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COMPANY NEWS AgraQuest relocation Biotechnology firm AgraQuest of California is transferring manufacturing operations to a $7 M facility in Tlaxcala Mexico. The firm which specialises in natural pest control products will use the facility to manufacture its new environmentally friendly fungicide Serenade. The fungicide is currently being produced by a third party contractor in the US but production will be handled by the Tlaxcala facility when it begins operating in March 2001. The plant was acquired from pharmaceutical firm Abbott Labs in December 2000 through funds generated from a $15 M private placement (http:// agraquest.com). PGR claims disputed BASF has heavily criticised claims by Syngenta that trinexapac-ethyl (Moddus) is the only plant growth regulator to increase rooting tillering and control lodging.BASF says chlormequat achieves the same results and at much lower costs. Both plant growth regulators are anti-gibberellins but Moddus blocks gibberellin synthesis near the end of the pathway which causes a very rapid halt to growth. There is also often a rush of compensatory growth following Moddus application. Trinexapac-ethyl also requires a relatively high temperature at which to operate unlike chlormequat. Disputes …American Cyanamid settlement Over 400,000 farmers may recover overpayments they allegedly made for chemicals manufactured by chemical producer American Cyanamid. American Cyanamid has agreed to settle two lawsuits involving the sale of its crop protection chemicals.While agreeing to the settlement American Cyanamid vigorously denies all allegations raised by the lawsuits. The crop protection chemicals involved were sold in all 50 US states and the District of Columbia. The bulk of the sales were made in the Midwest of US with the top five states in terms of Please send any contributions to the NEWS sections in Pesticide Outlook to Hamish Kidd The Royal Society of Chemistry Thomas Graham House Science Park Cambridge CB4 0WF. FAX +44 (0)1223 420247; email KIDDH@RSC.ORG. 82 Pesticide Outlook – June 2001 This journal is © The Royal Society of Chemistry 2001 total purchasers being Iowa Illinois Minnesota Indiana and Missouri. According to the terms of the settlement those eligible to participate must have purchased crop protection chemicals manufactured by American Cyanamid for their own consumption and not for resale during the period from 30 January 1991 through 27 June 1997.…Monsanto / Aventis settle Monsanto and Aventis have settled lawsuits relating to the development and commercialization of GM varieties of cotton. The settlement relates to intellectual property for common traits and stacking of multiple insect protection traits. Monsanto will permit Aventis to license Monsanto’s Roundup Ready and Bollgard technologies in Aventis’ FiberMax cotton varieties in the US. Aventis will license its insect-resistant management patents relating to Bacillus thuringiensis genes to Monsanto.Other existing cotton transformation patents will be cross-licensed. Sales and acquisitions …Bayer rejects call for split Bayer has rejected calls from a shareholder to split into three parts. It has also confirmed it is considering acquiring DuPont’s drugs business and Aventis CropScience. Tweedy Browne & Co which holds 0.1% of Bayer shares proposed splitting up Bayer into chemicals drugs and agrochemicals businesses. But Bayer says this would be detrimental to long-term shareholder value. However Bayer has been forced to allow shareholders to vote on the motion. Bayer says its present structure helps in the running of the business and allows it to capitalise on existing synergies and provides scope to move quickly on acquisition opportunities in the life science sector.The company is to seek shareholder approval to use a capital increase to raise up to EUR 8 bn for acquisitions. …BASF sells cyanazine products to Feinchemie Schwebda in Eschwege BASF sold the entire business based on the active herbicide ingredient cyanazine for the European economic region to the German company Feinchemie Schwebda of Eschwege. The active ingredient targets grasses and broad-leaf weeds in maize soybean cereals and vegetables and is marketed under the tradenames Bladex Fortrol and Bullet. Cyanazine had been acquired by BASF as part of the American Cyanamid take-over. This acquisition by Feinchemie Schwebda follows its recent acquisition of carbetamide and dimefuron and of some European registrations of bifenox from Aventis Crop Science (http:// www.feinchemie-fcs.com).…Monsanto buys fungicides and herbicides In order to increase its share in its second largest market Monsanto is seeking to purchase fungicide and herbicide producers in France. It is understood to be interested in acquiring parts of Aventis Crop Science although it is also rumoured that Bayer is also interested in the acquisition. The sale of genetically modified organisms has been suspended in France by Monsanto for the time being. …Mitsui & Co Ltd of Japan through a wholly owned subsidiary entered the US crop protection market and expanded its global Agri-Science operation by completing the purchase of Thermo Trilogy Corp assets from Thermo Electron Corp. The new company is called Certis USA. The acquisition includes production facilities in Wasco CA Decatur IL and Cardiff UK. Certis headquarters will remain in Columbia MD. It will be a leading producer of foliar Bacillus thuringiensis bioinsecticides neem-based botanical biopesticides and beneficial viruses nematodes and pheromones. (http://www.mitsui.co.jp) DOI 10.1039/b104730m

ISSN:0956-1250    

DOI:10.1039/b104730m

出版商:RSC    

年代:2001

数据来源: RSC

摘要:

IN PRAISE OF DDT Amir Attaran of Harvard University’s Centre for International Development argues the case for the retention of DDT in the battle against malaria as the POPs Convention reaches the signing stage Following an agreement at Johannesburg in December 2000 more than 100 countries signed the Convention on Persistent Organic Pollutants (POPs) in Stockholm on 22-23 May 2001. This POPs Convention seeks to ban the production and use of 12 chemicals the so-called “dirty dozen” l the pesticides aldrin chlordane DDT dieldrin endrin heptachlor mirex and toxaphene l the industrial chemicals polychlorinated biphenyls (PCBs) and hexachlorobenzene which is also a pesticide l the combustion byproducts dioxins and furans One hard-fought exemption in this Convention was for the continued use of DDT for public-health use principally against mosquitoes that spread malaria.Malaria was eradicated from the developed world in the 1950s using DDT but it still affects more than 300 million people in the developing world and a million die from it annually. DDT now produced only in China and India is one of the best and certainly the cheapest antimalarial tools available even in the face of insecticide resistance in some areas. DDT started to get a bad press when populations of birds declined because of brittle eggshells through the largescale agricultural use of DDT. The public health use of DDT however involves the application by trained sprayers of small quantities of DDT on the interior walls and eaves of homes in endemic regions.The quantities involved are minimal (2 g m–2) and unlike agricultural uses which inject tonnes of DDT into the outdoors indoor house spraying results in little harmful release to the environment. No other cheap insecticide is as effective as DDT against malariatransmitting mosquitoes and attempts to stop its public health use under pressure from environmental groups has resulted in an increase in malaria. The examples of this are striking. South Africa had been almost malaria-free since using DDT in the 1940s. But under pressure from environmentalists it switched to other insecticides in 1996. This allowed a particularly aggressive mosquito species (Anopheles funestus) to re-invade South Africa after a 50-year absence leading to a dramatic resurgence of disease malaria cases rose from 4117 in 1995 to 27,238 reported cases in 1999 (or possibly as many as 120,000 judging by pharmacy records).Neighbouring Swaziland which never stopped using DDT experienced no such resurgence. Faced with this mounting epidemic South Africa was forced to resume DDT use last year. These results are not unique. Starting in the 1950s Sri Lanka used DDT to lower malaria from 2.8 million cases and 7300 deaths to 17 cases and no deaths. Progress was reversed after the US government cut funding for the program and within a decade Sri Lanka rebounded to half a million cases. Despite these obvious benefits of retaining DDT for public health use some environmentalists urge that the human health risks of DDT justify its being banned precautionarily.But this argument churns the very notion of “precaution” to nonsense in the vast epidemiological literature there is not one adverse human health effect of DDT exposure which has withstood independent experimental replication while many studies show the consistent health benefit of DDT in malaria control. Banning DDT precautionarily therefore illogically places speculative risks glimpsed only through animal toxicology studies over the known and large human health benefits in malaria control. The health risk and benefit must accordingly be balanced just as they are when physicians administer highly toxic medicines to obtain a greater therapeutic benefit. Alternatives to DDT house spraying (for example pyrethroid-impregnated bednets and integrated vector management) can substitute in some but not all cases.Research is also being carried out on the development of new safer insecticides and anti-malarial vaccines but until there is an effective low-cost alternative there is a strong case for retaining DDT for antimalarial use in developing countries. While the POPs Convention gives DDT a reprieve in the form of an exemption for public health use more voices are urgently needed to ensure that poor and politically weak developing countries are allowed to use DDT without fear of retribution from environmentalists and well-meaning aid agencies whose poorly informed pressures have been so damaging – and fatal – in the past. DOI 10.1039/b104731k This journal is © The Royal Society of Chemistry 2001 Pesticide Outlook – June 2001 Further reading Attaran A.; Maharaj R. (2000) DDT for malaria control should not be banned. British Medical Journal 321 1403–1404. Attaran A.; Roberts D.; et al. (2000) Balancing risks on the backs of the poor. Nature Medicine 6(7) 729–731. Curtis C. F.; Lines J. D. (2000) Should DDT be banned by international treaty? Parasitology Today 16(3) 119–121. Kidd H (2000) POPs negotiations in Bonn. Pesticide Outlook 11(3) 123. Roberts D.; et al. (2000) DDT house spraying and re-emerging malaria. Lancet 356 330–332. http://irptc.unep.ch/pops/ http://www.fightingmalaria.org/ VIEWPOINT 83

ISSN:0956-1250    

DOI:10.1039/b104731k

出版商:RSC    

年代:2001

数据来源: RSC

摘要:

REGULATORY NEWS European ruling on generic pesticides Intellectual Property lawyers from Addleshaw Booth & Co have set an important legal precedent in the European Court of Justice (EJC) to allow producers of generic pesticides to compete with the world’s largest manufacturers. The firm was acting on behalf of Clayton Plant Protection Ltd. in a dispute brought by Monsanto plc who challenged a decision by the UK Pesticides Safety Directorate (PSD) which allowed Clayton to sell a glyphosate product essentially identical to Roundup. Monsanto had been seeking to extend their protection by submitting further unsolicited data to the PSD and claiming that generic producers had to match such data. The EJC ruling was that this unfairly stifled competition and that when an application is made for authorisation to market a generic product equivalent to a product already on the market then it should rely only upon the same data that was submitted in support of the original application Italian government forced to biotech compromise The Italian government has retreated from its tough stance on biotechnology following a protest by influential scientists.It has agreed to field trials to assess the impact of GMOs. The government has been strongly influenced by the Green Party and possibly by the Roman Catholic Church. It has refused to implement the EU directive on biotechnology patenting and will not allow imports of genetically modified organisms even when these are EU-approved.However it is thought that these influences may now be on the wane. The centre-right alliance which may shortly come to power backed the scientists. Italy has only 46 biotechnology companies. Assobiotec the industry association says Italy now faces an opportunity of rare strategic importance. 84 SP dip containers under scrutiny UK government advisors have raised concerns over containers for synthetic pyrethroid sheep dips. Organophosphate sheep dips were withdrawn for 10 months in the UK in 2000 while improved containers were developed. Now synthetic pyrethroids which can be 1000 times more active might be similarly regulated unless producers improve on the packaging. According to the Veterinary Products Pesticide Outlook – June 2001 This journal is © The Royal Society of Chemistry 2001 Committee there are defects in the container design for these substances.Concerns are focusing on the ease of opening of the containers spillage and the dip pooling cap. Exposure to organophosphates has been associated with chronic ill health but there are fewer operator concerns over synthetic pyrethroid usage. Brussels threatens action over Biocides Directive Legal action could be taken by the European Commission against 11 member states if the 1998 Biocides Directive is not transposed into national law within two months. The law should have been in force by May 2000. Safety and environmental standards for products such as disinfectants and pesticides for non-agricultural use are set out by the Directive and a new procedure for the approval of biocide products was introduced.The Directive has already been transposed in Italy Sweden Denmark and Austria. US pesticide re-assessment postponed The deadline for the Environmental Protection Agency to withdraw from a proposed settlement in a lawsuit involving a schedule for pesticide reassessments has been extended from 2 March to 19 March 2001. On the last day of the Clinton administration the EPA and the Natural Resources Defence Council entered into a consent decree that would impose additional deadlines on the EPA as it conducts pesticide safety reassessments under the Food Quality Protection Act of 1996. Before it can take effect the settlement must be approved by a federal court in California.EPA moving forward on pesticide review The Environmental Protection Agency has re-assessed the safety of about half of the riskier pesticides that it planned to review under the federal food safety law of 1996. As of October 2000 the EPA had reassessed 2275 of 5542 tolerances for group 1 pesticides 424 of 1684 tolerances for group 2 pesticides and 521 of 880 group 3 pesticides. The EPA raised 183 tolerances retained 1688 lowered 146 and revoked 1487. In group 1 of the 225 active ingredients reviewed 159 were for pesticides used on food and 66 were pesticides no longer used on food. By 2006 the FQPA requires the EPA to have reassessed 8961 pesticide tolerances.UK government funds health investigation into OPs The Ministry of Agriculture Fisheries and Food announced in mid-March an extended research programme costing £1.4 M into the effects of organophosphates (OPs) on human health. Government funding of an analytical survey of health complaints by personnel involved in the dipping of sheep is also being undertaken. The all-party OP parliamentary group approved the announcement but criticised the time taken to have got to this stage. The OP Information Network a campaign group criticised the rejection of research proposals from independent researchers with extensive clinical experience of OP poisoning. Halting diazinon Despite an agreement between the Environmental Protection Agency and the manufacturer (Syngenta) to withdraw diazinon from home garden uses by 2004 six state attorneys general are pressing major retailers to immediately withdraw the herbicide.The attorneys general claim that the EPA’s own assessment shows the product to be unsafe but Syngenta maintain that the product is safe and that the voluntary withdrawal was a commercial decision. CPA calls for action to ensure pesticide tax stays away Although the threatened pesticide tax was absent from the March UK budget the Crop Protection Association (CPA) calls for pesticide manufacturers farmers and distributors to pull together urgently to deliver the voluntary measures acceptable to the government. Agreement is expected soon between the industry and government on the environmental factors against which the industry will be measured.The first report is aimed to be back to the government by 1 October. Some measures can be implemented quickly such as promoting best practice producing pesticide environmental data sheets and appointing a biodiversity officer for the industry. The pesticide stewardship consortium representing the agrochemical and agricultural industries are considering the 27 measures proposed as an alternative to the pesticide tax. The final protocol is DOI 10.1039/b104732a due to be agreed within 8 months leading to a pilot scheme within 1 year on-farm uptake within 2 years and the involvement of 30% of arable land by 2006.A summary of the CPA measures can be downloaded from http://www.cropprotection. org.uk/ Rotterdam Convention Export notification procedures drawn up in the Rotterdam Convention which cover export of hazardous chemicals and pesticides restricted or banned in the EU are being applied by Cefic (the European Chemical Industry Council) and the European Crop Protection Association (ECPA) on a voluntary basis. The Convention is expected to take two years to implement fully. Prior informed consent has to be secured before the materials are exported. Signing the POPs treaty The Persistent Organic Pollutants (POPs) Convention agreed at Johannesburg in December 2000 will be signed was signed in May 2001 in Stockholm by more than 100 countries including the USA.For more information on the POPs Convention see Pesticide Outlook 2000 11(3) 123. Picoxystrobin receives its first registration On 31 May 2001 Syngenta announced the first registration worldwide of its new broad-spectrum strobilurin fungicide picoxystrobin. It has been granted registration in Germany for use on wheat barley oats and rye and will be marketed as Acanto®. This is the first of a number of cereal fungicide registrations expected largely in other European countries. Further information is available at http://www.syngenta.com. The next issue of Pesticide Outlook will contain an article on strobilurins especially picoxystrobin. EC lists substances requiring strict water environmental protection measures The European Commission has developed a procedure that will enable the listing of priority substances (PS) for which farreaching measures must be taken to protect aquatic environments.In addition priority hazardous substances (PHS) will be listed for which even more stringent measures are required to protect these environments. A third list has been drafted of 11 substances for which classification as PS or PHS is uncertain. It is proposed that a formulation be drawn up within 2 years to regulate PS emissions and establish water quality standards these substances are alachlor benzene chlorfenvinphos dichloromethane 1,2-dichloroethane diuron isoproturon nickel simazine and trichloromethane. For PHS emission control proposals must lead to a complete phasing out of discharges over a 20-year period these substances are brominated diphenyl ether (only pentabromodiphenyl ether) cadmium chloroalkanes hexachlorobenzene hexachlorobutadiene hexachlorocyclohexane mercury nonyl phenols polycyclic aromatic hydrocarbons pentachlorobenzene and tributyl tin compounds.No decision has yet been made on the substances and substance groups that are under consideration as priority substances; these are anthracene atrazine chlorpyrifos diethylhexylphthalate endosulfan lead naphthalene octyl phenols pentachlorophenol trichlorobenzene and trifluralin. These proposals will be considered by the European Parliament and the Board of Environmental Ministers over the next few months.An Expert Advisory Forum drawn up from all EU member states and the European chemical industry organisation Cefic will also be involved in the discussions. MAFF is dead – long live DEFRA Following the recent UK General Election the functions of the former Ministry of Agriculture Fisheries and Food (MAFF) including pesticide regulation will be carried out by a new Department for Environment Food & Rural Affairs (DEFRA). DEFRA also brings together the Environment Protection Group and the Wildlife and Countryside Directorate of the former Department of the Environment Transport and the Regions (DETR) and responsibility for certain animal welfare issues and foxhunting from the Home Office. DEFRA will also sponsor a number of important non-Departmental Public Bodies e.g.the Environment Agency the Countryside Agency Meat and Livestock Commission Kew Gardens English Nature Food from Britain and the Royal Commission on Environmental Pollution. For further details on the web see http://www.maff.gov.uk/ (this website will be reorganised shortly to reflect the recent changes). Another name change The Global Crop Protection Federation (GCPF) previously known as GIFAP has changed its name again to CropLife International. It is styling itself as a global federation representing the plant science Pesticide Outlook – June 2001 REGULATORY NEWS industry – i.e. broadening its scope to include both crop protection and agricultural biotechnology.It is also dedicating itself to become more attuned and responsive to the issues and concerns of society. Snippets …replacement for gamma-HCH Bayer product expected in two years Bayer has a replacement for gamma-HCH. UK894 contains imidacloprid and betacyfluthrin for use against insects such as adult flea beetle cabbage stem flea beetle and aphids on oilseed rape. Results have surpassed those of gamma-HCH. UK894 is already sold in some countries as Chinook. …The European Commission have added the following active substances to Annex I of Directive 91/414/EEC on placing plant protection products on the market amitrole diquat pyridate thiabendazole bentazone and fenhexamid. …EPA abandons split biotech registration The type of split pesticide registration which permitted StarLink corn to be approved for animal feed but not for human use has been eliminated as a regulatory option by the US Environmental Protection Agency.The decision was quickly endorsed by the US biotechnology industry. Research commissioned by the EPA has found that StarLink’s Cry9C protein is eliminated from the corn by wet milling but not by dry milling. …accelerated approval of pesticides in the Netherlands The EU Commission called on the Netherlands to speed up their approval proceedings from generic pesticides and parallel imports. The commission initiated the second stage of a lawsuit for treaty infringement against the Netherlands. Approval of new pesticides already manufactured and marketed in other EU states can take up to 2 years in the Netherlands. The EU Commission considers 45 days a more appropriate period. …European Union settles differences with China over intellectual property protection China has reached an agreement with the European Union in which new members of the EU will benefit from the same intellectual property protection as the other member countries. China had previously refused to give protection to pharmaceutical and agrochemicals from Austria Finland and Sweden which only joined the EU in 1995. 85

ISSN:0956-1250    

DOI:10.1039/b104732a

出版商:RSC    

年代:2001

数据来源: RSC

摘要:

AWARD AMERICAN CHEMICAL SOCIETY HONOURS DON CROSBY Ann Lemley from Cornell University reports of this year’s recipient of the International Award for Research in Agrochemicals The International Award for Research in Agrochemicals sponsored by BASF and awarded by the Agrochemical Division of the American Chemical Society was presented to Emeritus Professor Donald G. Crosby on Monday April 2 2001 in San Diego California. Dr. Crosby was presented with a cheque from BASF and a plaque from the Agrochemical Division that extolled his creative research on pathways of transformation of pesticides in the environment emphasizing chemical and photochemical pathways. Dr. Crosby gave the award address in which he discussed the powerful influence that ultraviolet radiation particularly sunlight has on pesticides.He showed how this theme has been the dominant aspect of his research over the years and discussed in some detail important direct and indirect photochemical transformations illustrating his talk with seminal work carried out in his laboratory. Dr. Crosby’s talk was followed by a variety of presentations by former graduate students colleagues from the University of California at Davis and colleagues from all over the US and the world. Presentations were liberally interspersed with warmth and humor and fond recollections of working with Dr. Crosby (including some vintage pictures). Dr. Fritz Fuhr from Institute of Chemistry and Dynamics in Julich Germany and a former winner of the International Award in Agrochemicals described his sabbatic visits to Crosby’s lab and how his discussions there influenced his own research using wind tunnels to study the volatility and photochemistry of pesticides.Dr. Richard Zepp of the US Environmental Protection Agency described his work on the influence of dissolved organic matter on agrochemical photoreactions in the aquatic environment and how this work depended on the pioneering studies by Don Crosby. Dr. Donald Mackay from Trent University in Ontario Canada also spent some sabbatic leaves at Crosby’s lab and spoke about his work on assessment of agrochemicals for their persistence bioaccumulation toxicity and long range transport and how the environmental fate work of the Crosby group was an important aspect of these broader models.A hallmark of Crosby’s impact through the years has been the variety of graduate students from different fields with whom he worked and who have now developed important and successful careers in academia industry and government laboratories. Many of the projects with these graduate students were collaborations between Crosby and colleagues at UC Davis who were in other fields such as toxicology or wildlife specialties. Crosby brought a multidisciplinary approach to the solution of environmental problems before it became the fashionable thing to do. Born in Portland Oregon in 1928 Don Crosby grew up in Southern California. He received his AB in chemistry at Pomona College (1950) and a PhD in chemistry and biology at CalTech (1953).In 1961 he was invited by Chancellor Emil Mrak to join the University of California at Davis and has been there ever since. As Professor in the world’s first Environmental Toxicology Department much of his research centered on pesticide photochemistry and aquatic metabolism continuing his research and teaching even well past his 1991 “retirement.” Don organized the ACS Division of Pesticide Chemistry (now the Agrochemicals Division) in 1968 served as its first chairman (1969) and Councillor (1971-80) was on the Board-Council Committee on Environmental Improvement for 6 years and became a Division Fellow in 1972. With Wendell Phillips and Jim Minyard he initiated the Division’s International Award in Pesticide Chemistry and presented the first Award to his UC colleague John Casida in 1969.also served 9 years as U.S. representative on the IUPAC Commission on Pesticide Chemistry Former students made presentations about reactions rates of mercury in the gas phase the role of hydroxyl radicals and carbonate radicals in the photodegradation of pesticides applications of accelerator mass spectrometry in assessing the fate of chemicals and fate of turf pesticides in aquatic ecosystems. Dr. Donald Crosby is a very worthy recipient of the International Award for Research in Agrochemicals and the award symposium was a joyous celebration for all involved. Pesticide Outlook – June 2001 This journal is © The Royal Society of Chemistry 2001 DOI 10.1039/b104734p 86

ISSN:0956-1250    

DOI:10.1039/b104734p

出版商:RSC    

年代:2001

数据来源: RSC

摘要:

Resistance …Strobilurin resistance increasing Dow AgroSciences reports that resistance by wheat mildew spores to strobilurin fungicides has risen from less than 5% in 1999 to 70% in Scotland and 60% in south-east England in 2000. Equivalent figures in Germany and France in 2000 are 77% and 80% respectively. The frequent spraying by growers of low rates of the strobilurins (many wheat crops are given 3 or even 4 applications) without the use of mixtures of other fungicide products are seen as a major cause. The practice is against the recommendations of the inter companies’ Fungicide Resistance Action Committee (FRAC) that recommends a limit of 2 treatments per season thereby prolonging the lives of the strobilurins. …Syngenta defends new seed treatment Syngenta has developed a new second generation seed treatment for control of insects such as virus-carrying aphids in sugar beet and other crops.Thiamethoxam sold as Cruiser Adage and Helix in some markets is a second generation member of the neonicotinoid class of chemistry. It is seen as a challenger to imidacloprid sold as Gaucho which dominates the sugar beet market with some 75% share. The first pest resistance to imidacloprid has been recorded in glasshouse crops in Greece and fear has been expressed that its chemical similarity to thiamethoxam could increase the speed of resistance development to both compounds. Syngenta argues however that its compound affects different receptors in aphids is used at lower rates and distributed in the plant more quickly.…breeding can help to protect bees from Varroa mites The Varroa mite has become a serious problem for bee keepers as they reduce the bees’ energy and productivity and can kill a colony within two years unless treated with pesticides. Unfortunately even these expensive chemicals are becoming less effective as the mites develop resistance to them. Workers at Minnesota State University have bred a colony of bees that were able to remove the parasites and their larvae from the hives and maintain honey production levels. Unfortunately when more than 15% of the bees were infested they were overwhelmed by the mites but used in conjunction with pesticides they are clearly a useful tool for the protection of bees from this harmful parasite.DOI 10.1039/b104736c Organic production …Serenade biofungicide approved as an organic agriculture product AgraQuest Inc has entered the organic farming industry after a new formulation of its biofungicide Serenade was registered by the US Environmental Protection Agency and added to the list of approved crop protection products by the Organic Materials Review Institute (OMRI). The California Environmental Protection Agency’s Department of Pesticide Registration and the Washington State Department of Agriculture’s Organic Food Program also have approved the new formulation. Serenade is based on AgraQuest’s patented strain of Bacillus subtilis a microorganism that is effective against several crop damaging pathogens including powdery mildew walnut blight Botrytis bunch rot and fire blight.The original wettable powder and the newly registered organic formulation of Serenade are approved for use on vines fruits hops peanuts vegetables and walnuts. Three new crops - carrots broccoli and onions - have been added to the US EPA label for the organic formulation. Used on grapevines Serenade is the one product that effectively controls all major diseases including powdery mildew Botrytis bunch rot and sour rot in addition to suppressing downy mildew. …organic orchards are more profitable than conventional ones Workers at Washington State University have compared orchards growing Golden Delicious apples using conventional integrated and organic methods.The study lasted six years and although they took longer to reach profitability by the end of the trial organic methods were placed first in environmental sustainability profitability and energy efficiency. Integrated practices were placed second with conventional farming methods last. In a blind taste test untrained tasters rated the organic apples as the sweetest. (For more information see J. P. Reganold et al. 2001 Sustainability of three apple production systems. Nature 410 926-930). …garlic – new organic insecticide? Organic farmers are using increasingly large quantities of ‘natural’ insecticides to help combat the infestation of their crops by phytophagous insects.Garlic Barrier is a strong liquid garlic concentrate that when diluted and sprayed onto crops repels Pesticide Outlook – June 2001 This journal is © The Royal Society of Chemistry 2001 Methyl bromide replacements Dow AgroSciences has developed a new soil fumigant InLine proven to be as good as methyl bromide in eliminating soil dwelling organisms that damage crops. Inline contains around 60% 1,3-dichloropropene and 35% chloropicrin. Strawberry plots treated with InLine have generated crop yields of 95-110% compared to methyl bromide according to a study conducted by US Agricultural Research Services in California. Methyl bromide is currently sold at $3.50/lb while InLine sells for just below $2/lb. The company is awaiting state and federal approvals to use Inline on strawberries as a replacement for R&D NEWS insects and thereby protects the crop.It is claimed that the odour disappears in minutes but the repellent effect lasts it is harmless to birds farm workers and the environment (http://www.garlicbarrier.com for more information). …organic Austria? Within the European Union Austria has more organic farming than any other member state with approximately 10% of its land in organic production. The government has encouraged this by using European subsidies to support farmer conversions. It is now being urged by a consortium of four environmental groups (Greenpeace WWF Global 2000 and Vier Pfoten) to double this commitment. …the Philippines goes organic The potential market for organic food production has been identified by the Philippine Department of Agriculture as a means of establishing a dependable and high value export market.As such the Department is to establish a committee designed to encourage and support farmers who wish to change to organic production. The programme will be monitored by certification programmes that will comply with US and EU organic standards. …Japanese organic supply unit Sumitomo has announced that it is to establish a new subsidiary in Japan to advise organic growers on preventative insect control use of crop protection agents in organic crops and marketing organic produce. The subsidiary Nihon EcoAgro will also supply products for use in these crops.87 R&D NEWS methyl bromide. Methyl bromide is schedule to be phased out by 2005. Exotic water weed control The USDA Agricultural Research Service (ARS) has entered into a 3-year Cooperative Research & Development Agreement (CRADA) with SePRO Corporation of Carmel Indiana to mass produce and formulate the fungus Mycoleptodiscus terrestris as a biocontrol agent to control hydrilla. Hydrilla is an exotic weed originally from Asia that grows so competitively with other aquatic plants that biological diversity may be threatened in many lakes and streams. It is notorious for clogging marinas snarling fishing lines and interfering with flood control and hydroelectric power generation. In times of drought these weeds can also obstruct the flow of irrigation water.Destruction of sheep dip solutions The EA Technology Environmental Group has shown that the patented DEM Cell electrochemical oxidation process can provide effective economical and environmentally safe destruction of organophosphate (OP) sheep dip solutions. It has been shown in 18 months of laboratory and pilot-scale trials that the DEM Cell which uses dished electrode membranes to oxidise toxic organic substances breaking them down to carbon dioxide nitrogen and water rapidly destroyed sheep dip solutions containing diazinon. Heat treating packaged fruit Instead of the use of ethylene dibromide (EDB) to control fruit flies exporters on the Cook Islands are using a hightemperature forced-air (HTFA) treatment comprising a treatment at 47.2°C for 20 minutes in sealed chambers.The method has been demonstrated with papaya and mangoes and there are plans to expand exports to other produce including aubergines. If carried out properly the treatment even enhances the market quality of the fruit. It produces an even colour on the fruit and slows down the rate of internal ripening. This helps to extend fruit shelf-life and the fruit flesh does not develop the bitterness which is characteristic of fruit treated with EDB. The treatment can also be adapted to the control of temperate pests in avocadoes litchis bell peppers nectarines and apricots. Pesticide Outlook – June 2001 88 Plant protection signalling by day and night De Moraes et al.(Nature 2001 410 577- 580) have shown that tobacco plants use different blends of volatile compounds by day and by night. In daylight plants under attack by herbivores emit blends that attract parasitic or predatory insects which destroy the herbivores. By night attacked tobacco plants release volatiles (mainly blends of small unsaturated derivatives of fatty acids) that repel nocturnal pregnant moths which are looking for somewhere to deposit their eggs. Duo controls Melaleuca Scientists at the USDA Agricultural Research Service Invasive Plant Research Laboratory at Fort Lauderdale Florida are working with colleagues from the University of Florida University of Adelaide in Australia the CSIRO and the ARS Australian Biological Control Laboratory to develop a team of two organisms – the Fergusonina fly and the nematode Fergusobia – to help to limit the spread of the invasive weed Melaleuca quinquenervia.The female Fergusonina fly carries the nematodes in her ovaries and deposits them along with her eggs into young Melaleuca buds. The female Fergusobia nematodes and the fly larvae that hatch then feed on enlarged plant cells created by the microscopic nematodes. Eventually galls form on infested buds preventing flowers and seeds from developing. Plant-stroking machine Researchers from the University of Greenwich and Hadlow College have developed a plant-stroking machine which they believe can improve the quality of young plants especially vegetables and bedding plants – producing shorter stockier specimens – by a process called thigmomorphogenesis (a change in growth or form as a result of touch).The electronically controlled machine brushes the tips of young plants. The idea is based on the fact that plants generally respond to an increased degree of physical disturbance from touch or wind movement by growing shorter and stockier. It is hoped that thigmomorphogenesis could help to overcome some of the growth problems of plants in protected environments without resorting to the use of chemical growth regulators. See http:// www.hadlow.ac.uk/chelsea2.htm Tesco boosts organic crop research The UK supermarket chain Tesco is aiming to set up the biggest research project into organic crop production in the world.Large tracts of agricultural land have been set aside for study into organic production and a special research centre funded substantially by Tesco has been established at Newcastle University (http://www.tesco. com/organic/). Snippets …a new active ingredient the first in the blight market since 1994 joins battle with fluazinam cymoxanil and mancozeb. Zoxium comes from Rohm and Haas and will be marketed in mixture with mancozeb as Electis by Interfarm UK and as Roxan by Dalgety. The compound has a novel mode of action and no resistance to any phenylamide resistance strain has been detected in the laboratory. …scientists at the Horticultural Research Institute (HRI) Wellesbourne have isolated and patented two genes from bacteria that produce substances toxic to certain nematodes. Added to a carrier bacterium they could be used to control nematode pests. …Celgro Corp. of Warren New Jersey USA have been awarded a US patent for S-imazalil the chirally pure version of imazalil covering the composition and methods of use of the fungicide. …the new Syngenta herbicide pyriftalid which controls grasses (especially Echinochloa) in rice paddies has received its first registration in South Korea. Further registrations are expected to follow in major rice-growing countries throughout Asia. …according to a report in Nature Biotechnology (2001 19 371) George Wagner and colleagues at the University of Kentucky at Lexington have genetically modified tobacco plants so that they produce large quantities of a aphidrepelling substance called cembratrienediol within tiny glands called trichomes. The modifed plants were significantly less colonised by aphids than in normal unmodified plants.

ISSN:0956-1250    

DOI:10.1039/b104736c

出版商:RSC    

年代:2001

数据来源: RSC

摘要:

Phoenix to release new GM insect terminator In summer 2001 Phoenix will carry out the first release of a genetically modified insect which should protect cotton against harmful insects. The GM insect dubbed terminator by farmers is sterile but sexually active and it is hoped will breed with the harmful insects thus reducing mating between non-sterile insects so that eventually there are no offspring. Around 3600 larvae will be released in a sealed field. The terminator has been given a fluorescent jelly fish gene in order that the process can be monitored. Greenpeace is opposed to the experiment saying that because insects breed quickly mutations could arise which might be difficult to control. It also has doubts as to whether the insect is truly sterile.GM maize in Austria An EC scientific committee for plant evaluation has made public its opinion against the prohibition in Austria of a genetically modified (GM) maize which is tolerant to the herbicide glufosinateammonium (Liberty). The maize supplied by Aventis was approved by the EU in 1998. The committee reports that it can find no scientific justification for the ban. The Austrian government has argued that the maize may have a negative impact on the alpine ecosystem. This is the third time that an EC committee has been opposed to decisions made by member states regarding the banning of GM crops. GM crops in China In China several genome-research centres are being spun-off from state-run academies and institutes.Other Asian countries notably Japan Korea and Singapore are recognising China’s potential and seeking collaborative projects. But such projects will suffer from a poor domestic legal framework weak enforcement of intellectual property rights and poor compliance with international standards; for example market analysts are sceptical about China’s signing of the International BioSafety Protocol. There are concerns about the spread of genetically modified (GM) crops in China. The country has been cautious about edible GM crops but has VISIT OUR WEBSITE Have a look at the Pesticide Outlook Website on http://www.rsc.org/po DO1 10.1039/b104738h BIOTECHNOLOGY NEWS rapidly commercialised non-food crops such as GM cotton and tobacco.DuPont seed ruling A federal judge has determined that a licence held by DuPont to sell seeds containing Monsanto’s Roundup herbicidetolerant technology was terminated by DuPont’s acquisition of Pioneer Hi-Bred on 1 October 1999. Monsanto says the ruling means that all sales of Roundup Ready soybean and canola seeds by Pioneer since October 1999 were unauthorised. DuPont is to appeal. Syngenta funds sequencing of a key wheat pathogen In an attempt to find leads for new more specific and environmentally friendlier ways of protecting crops from attack by fungal pathogens Syngenta has signed an agreement with Plant Research International on a project to sequence the genome of the pathogen Mycosphaerella graminicola (Septoria tritici).A key part of the project will also examine the interactions between the fungus and the pathogen with a view to its exploitation to develop wheat cultivars with a durable resistance to the pathogen. Enhancing natural defence mechanisms It has been known for many years that plants produce a number of natural chemicals that help to protect them from attack by insects and pathogens. Many of these chemicals are produced in trichomes on the leaves and recent work reported in Nature Biotechnology (April 2001) has demonstrated that modification of the levels of trichome-specific cytochrome P450 enzymes gave a 20-fold increase in the levels of diterpenes in the trichomes and this increased the plant’s resistance to attack by aphids.Mosquito genome to be sequenced The 260 million base pairs of the mosquito (Anopholes gambiae) are to be sequenced in a joint programme between Celera Genomics and Genoscope. The genome will be broken into fragments and each piece Pesticide Outlook – June 2001 This journal is © The Royal Society of Chemistry 2001 Thailand halts GM crop trials Thailand has extended its ban on the commercial growing of GM crops to cover their testing in the field. It is expected that the move will end trials by Monsanto on GM maize and cotton. will be sequenced. Celera will then reassemble these into the complete genome. It is expected that the project will cost less than $10 M and that it will be completed by the end of 2001.Genes for resistance to soybean nematodes identified Soybean cyst nematode causes losses of $1 billion annually and they are very few varieties that show resistance to all 14 nematode races. Workers at the US Agricultural Research Service are examining soybean genes that are associated with resistance. Using microarrays 1200 genes from six different soybean cultivars have been screened for activity in nematode challenged and nematode free plants. This technique allows the workers to identify all genes that are associated with nematode attack and thereby to isolate gene products that are important in resistance (and susceptibility). UK “Farm Scale” Trials Concerns have been expressed by environmental groups over GM maize to be grown in Warwickshire as part of the UK Government’s official farm-scale trials. The site is within 2 miles of Europe’s largest research center for organic crops at Ryton near Coventry by the Henry Doubleday Research Association. The centre is home to one of the world’s foremost organic seed banks and protestors fear possible contamination of the seed bank. US biotechnology Monsanto revealed that in the USA 54% of the soybean area and 61% of the cotton area in 2000 were sown to genetically modified (GM) crop varieties; equivalent figures as forecast by the US Department of Agriculture for 2001 are 63% and 64%. However Monsanto’s GM NewLeaf potatoes modified to be resistant to Colorado beetle have been withdrawn after McDonald’s withdrew support. 89

ISSN:0956-1250    

DOI:10.1039/b104738h

出版商:RSC    

年代:2001

数据来源: RSC

摘要:

INSECT CONTROL Figure 1. Bipyramidal protein toxin crystals (each ca. 1m) produced by the bacterium Bacillus thuringiensis. Photo BACILLUS THURINGIENSIS IN PEST CONTROL H Denis Burges1 retired from Horticulture Research International (UK) describes the biology and present use of Bacillus thuringiensis (Bt) and its toxins then discusses their future courtesy of John Norris. Copyright Syngenta. natural environment. This character is of enormous practical diagnostic value. The name has stood the test of time and I believe it will continue to do so. Biology Bt was first found in Lepidoptera larvae. Cadavers often liquefied revealing body contents loaded with the developmental stages of the bacterium i.e. phase bright spores less phase bright bipyramidal crystals often mixed with vegetative phase dark rod-shaped bacterial cells many with a spore and a crystal clearly forming inside.Cadaver contents smeared over the bodies of healthy DOI 10.1039/b104591c 90 Introduction During the late 1940s when I was working on the control of insect pests in stored food I used to daydream about the perfect insecticide. I imagined a chemical systemic in the plant able to kill all pest insects and no other animals – certainly not beneficial invertebrates. It would be totally harmless to man suitable for addition to human food and preferably of nutrient value. Utter daydream? Little did I know that a protein with virtually all these desirable features had been tentatively marketed as the product Sporeine in France before the 1939–45 war but totally unrecognised for what it was! This wonder insecticide is contained in the bipyramidal toxin crystals (Figure 1) of the aerobic sporeforming bacterium Bacillus thuringiensis (Bt).Sporeine contained spores and toxin crystals of Bt both readily visible under the high power light microscope. The spore was regarded as a specific orally infectious invasive pathogen of lepidopterous caterpillars but no one realised that the main active ingredient was a complex of specific proteinaceous gut poisons called delta-endotoxins which formed the bulk of each crystal. However Sporeine was expensive and had many commercial disadvantages in comparison with the broad-spectrum contact insecticides developed so rapidly and effectively after the war.Many of these have since been banned while Bt has been developed into modern effective competitive insecticidal products listed by Glare and O’Callaghan (2000). The crystal is the key not only to the insecticidal action of Bt but also to its specific scientific name. This bacterium is a member of the Bacillus cereus group of soil dwelling bacteria. Apart from possession of the crystal all features are identical to those of B. cereus itself. However the ability to form the crystal can sometimes be lost and the resulting acrystalliferous strain becomes indistinguishable from B. cereus. Vice versa delta-endotoxin genes can be transmitted from a strain of Bt to B. cereus by direct cell to cell contact. The resulting crystalliferous B.cereus is indistinguishable from Bt. Over the years this has led to a simmering debate as to whether really only one species is involved. Recently a high degree of genetic similarity between the two species has been demonstrated by taxonomists resurrecting the debate. I perhaps among the majority of practically orientated bacteriologists stick to the name Bt because it is based on a functionally key character of prime ecological significance which distinguishes bacteria that are ever present in the 1 21 Withdean Ave Goring-by-Sea Worthing West Sussex UK Pesticide Outlook – June 2001 This journal is © The Royal Society of Chemistry 2001 larvae did not kill them so these objects had no contact action. If these same contents were generously coated on to a larva’s food feeding stopped within 20 min movement stopped often after two hours and larvae died in 1–2 days.Pure suspensions of crystals had the same effect and were demonstrated to be highly potent gut poisons with a specific mode of action. Sectioning the midguts of larvae at increasing time intervals after ingesting crystals showed a typical sequence. Cilia on the brush border of epithelial cells became entangled then the cells started to swell. Eventually the cells disintegrated and separated from the basement membrane filling the gut lumen outside the peritrophic membrane with a structureless mush. At or near larval death gut bacteria and Bt spores (if initially included with the crystals) invaded the body cavity and bred.However absolutely spore free but intact crystals injected into the body cavity did not upset the gut or kill the larvae. But gut symptoms ensued if before injection the inert crystals were first dissolved in vitro in alkaline buffer then digested by certain proteases releasing a stable mixture of smaller proteins the activated delta-endotoxins. Thus the activated endotoxins in the body cavity had actually penetrated gut epithelial cells from the body cavity side of the basement membrane demonstrating the specificity of their mode of action. Approaching these epithelial cells from the usual direction of the gut lumen each activated toxin molecule could be shown to bind with specific sites on the brush border cell membrane facing the gut lumen.The toxin then opened up lytic pores in the brush border membrane which destroyed control of movement of electrolytes and other solutes between gut lumen and epithelial cell cytoplasm causing the observed cell swelling. Thus the toxins alone were lethal. When toxins were applied orally symptoms and time to larval death were dose-dependent. What is the role of the spores? At rapidly lethal dosages of spore-crystal mixture spores germinate after insect death and bacteria permeate the cadaver. In some insect host species after lower sublethal dosages of crystal the high pH of the gut rapidly falls which allows spores to germinate in the gut and bacterial numbers to increase. Vegetative rods group near the basement membrane and produce hyaluronidase that erodes the membrane permitting penetration of bacteria into the body cavity while the larva is still alive.The resulting septicaemia increases mortality. When the body contents can support no more bacteria spores are formed allowing the species to survive until further healthy larvae are infected when they cannibalise diseased larvae or eat food fouled by faeces and by bacteria from disintegrating cadavers. Each Bt strain is highly potent in only a limited range of host species. Different strains may exhibit different ranges although these ranges frequently overlap. Thus there is a degree of strain specificity. Subspecies and host range Many methods have been used to identify and classify the thousands of strains of Bt which were collected from natural INSECT CONTROL sources in many decades of Bt research.These methods began with bioassays and traditional biochemical methods then serotyping and bacteriophage typing moving on to plasmid profiles sequencing and polymerase chain reaction (PCR) etc. The most useful early system proved to be serotyping based on H (or flagellar) antigens. The H serotypes led to the present growing list of subspecies now numbering over 80 listed by Glare and O’Callaghan (2000). Strains belonging to one subspecies attack predominantly one family of insects. Most e.g. kurstaki attack Lepidoptera; some e.g. israelensis attack Diptera; a few e.g. morrisoni (= tenebrionis) attack Coleoptera; a few invertebrates outside the Insecta such as certain nematodes are susceptible too (catalogued by Glare and O’Callaghan 2000).Most strains of Bt contain and express more than one delta-endotoxin gene. The various genes differ in their DNA sequences. The delta-endotoxins produced may differ in their amino acid sequences and the levels and ranges of insecticidal activity. Strains have many different combinations of delta-endotoxins with extensive overlap of individual toxins between subspecies. Accordingly there is only a weak correlation between bacterial subspecies and susceptible genera of hosts but a very strong correlation between particular toxins and host species. Classification of strains by specific activity due to combinations of toxins is rapidly becoming more important than classification by subspecies.Toxins are classified by amino acid sequence homology (Crickmore et al. 1998). At present 89 different delta endotoxin genes have been cloned from Bt and two other species (http://www.biols.susx.ac.uk/Home/Neil_ Crickmore/Bt/). de Maagd et al. (2001) have reviewed the likely course of evolution of the toxins in relation to their host insects. Study of the structure and function of the crystal is at the cutting edge of Bt research. In most Bt endotoxins there are two zones. The C-terminal zone is not part of the active toxin. It is believed to control crystal formation and on reaching the insect midgut it is cut off by proteases (Schnepf et al. 1990). In three toxins the N-terminal zone has been shown to be toxic and its three-dimensional structure revealed by X ray crystallography to consist of three domains I II III.Domain I comprising three alpha helices is involved in membrane insertion and pore formation while domains II and III are involved in receptor recognition and binding. Ecology The most obvious ecological niche for Bt is primary parasitism of insects. An inundative foliar spray outdoors usually kills at best 95% of larvae and foliage feeding adults leaving all other developmental stages unharmed. Exposed spores are rapidly killed by solar UV radiation while crystals are denatured rather more slowly. UV combines with weathering to inactivate deposits in 2-20 days depending on climate weather and position both on the leaf and in the foliar canopy.Natural spread of the bacteria to the next insect generation is poor so sprays have to be repeated frequently to continue pest control over the insect’s seasonal reproductive span. Carry over on foliage 91 Pesticide Outlook – June 2001 INSECT CONTROL until the next year is very poor. It depends on spores surviving passage through the guts of predators and in faeces as well as in host insect cadavers. Spores survive fairly well on reaching the soil by various means but return of spores from soil to foliage is poor. Surprisingly another ecological niche for Bt is that of a soil saprophyte. A wide variety of subspecies are fairly common in soil including israelensis (Martin and Travers 1989; Bernhard et al. 1997). That spores become airborne is evidenced by their presence deep in the polar ice cap (Martin and Travers 1989).Bt grows well in autoclaved soils that are near neutral to alkaline but not acid. However it does not grow readily in unheated soils. When spores were applied to soil their numbers declined progressively except for modest increases in early summer presumably in response to increasing soil temperature and to nutrients released in the soil by decay and freezing in the winter fallow period (A. Meikle personal communication). Thus Bt appears to be a poorly competitive soil organism. It is much less common than the ubiquitous soil bacterium B. cereus. For example it comprised 1.1% of B. cereus group isolates found in a survey of the Ryukyus islands in Japan (Ohba et al.2000). More surprisingly Bt is present among the bacteria on the surfaces of many species of plant leaf (Smith and Couche 1991). As to their origin they could have come from soil e.g. in wind blown dust although spores in sprays of Bt products survive on leaves only a short time. However visualisation of a vegetative rod of a non commercialised strain by Vaid and Bishop (2000) suggests an ability of Bt to grow and reproduce on certain leaves. Bt insecticides on land and in water Post 1939-45 war Steinhaus (1951) mass produced a sporecrystal preparation on agar in large Roux bottles for a historic field experiment. He successfully controlled the alfalfa caterpillar on field alfalfa in the USA. Thus encouraged he invited representatives of the fermentation industry to a meeting at a time when many companies had spare fermentation capacity.Hearsay has related that his audience misinterpreted the dosage required as 1g/acre. Excited they rushed off to grow his strain in their fermenters resulting in over six embryo products. However in fact several pounds weight per acre was needed to control field caterpillars still a highly feasible proposition. Whatever the production of Bt received a kick-start in the USA. Because of various teething troubles these products were not competitive with contact insecticides like DDT despite their obvious desirable biological qualities. Early field use took little account of what was known of Bt biology at the time. The spray technology was primitive following blindly practices for chemical contact insecticides.Three main companies survived in this field and progressively improved their products. Research followed two directions product development described in detail by Burges and Jones (1998a) and strain improvement (Jarrett and Burges 1986). Improving efficiency and efficacy drove down the cost of producing and applying Bt products. The fermentation and harvest processes were optimised (Bernhard and Utz 1993). Pesticide Outlook – June 2001 92 At harvest after filtration or centrifugation there was the option of making a liquid or a dry product both containing spores that must be kept alive and proteinaceous toxins that degrade relatively easily. A liquid avoids the cost and possible damage of drying is easier to mix and spray and has been developed recently into some very cost effective ready to use high potency products for ultra low volume application.However suspension agents are needed to prevent the particles settling during storage; relative instability of liquid formulations requires preservatives; some liquid products have difficulty in meeting a minimal shelf life of 18 months at ambient temperatures although I stored a 1961 emulsion for 18 years at 2–5 °C without measurable loss of potency. Powders incur the high cost of spray drying but they are lighter in weight to transport than liquids; their main advantage is long shelf life even at quite high temperatures. These features suggest a practical place for both types of product in fact both sell nearly equally.Post application spray quality and persistence have also been vastly improved. Spores and crystals being particulate are more difficult to spray than soluble active ingredients like many chemicals. Careful choice of fermentation ingredients as well as materials added at harvest reduces the formation of large particles and aggregates and also gives friability for the grinding of dry products. Free flow agents are added to dry products to make powders pour easily and suspension agents are added to support wettable powders in spray suspensions. Since Bt must be eaten to take effect good even persistent foliar cover is required which is attained by adding wetters stickers and UV protectants either to the on-shelf product or at spray mixing.Research has also developed a range of phagostimulants but these are not yet widely used industrially (Burges and Jones 1998a; Jones and Burges 1998; Bernhard and Utz 1993). The same types of formulation but containing ssp. israelensis are applied to water bodies to control mosquito and simuliid blackfly larvae (Burges and Jones 1998a). The most suitable products are those with the smallest particles that remain suspended in the water longest and so are most easily extracted by the filter feeding larvae. Formulation in ice pellets gives good suspension (Becker 2000). Particles sinking to the bottom are soon covered by mud and lost from the larval feeding zone. Some specialist granules have been developed for mosquito species with a variety of different feeding habits and other products for slow release to extend the interval between applications.The quality of the earliest products was very variable so methods for quality control were developed (Burges and Jones 1998a). In store dry products tended to absorb moisture from the air and cake solid. This was remedied by drying to 7% moisture content or less and storing in moisture proof containers. Sometimes plastic canisters of early liquids exploded in store due to gas production and build up of pressure particularly in warm climates. This build up was cured by improving the preservatives and by checking quality. Manufacturers cool-stored their liquids at 10 oC or less until release to wholesalers and some provided direct delivery to site of use in refrigerated bulk tankers.However the greatest quality control problem was measurement and standardisation of potency. It took comprehensive international co-operative research in the 1960s to demonstrate that spore count was a virtually useless potency indicator and that bioassay against a standard should be used (Burges 1967b). For bioassay of the early products based on ssp. thuringiensis a stable standard powder E61 was produced stored carefully and distributed (Burges 1967a). As soon as more effective subspecies were adopted by industry in the 1970s their greatly increased activity made E61 impracticable to use and two new homologous standard powders were produced for kurstaki and israelensis respectively.Two standard insects were agreed upon the moth Trichoplusia ni and the mosquito Aedes aegypti. The adoption of more Bt subspecies and of modified strains in the 1990s drove firms to using their own internal standard powders for the new strains. Many alternative easier less expensive potency measures were researched such as serological assays and various approaches to quantify crystal proteins. However all these have shortcomings due to the complexity of the reaction of Bt with its host insects. Therefore they should be used only in conjunction with bioassay. Potency is still quoted on labels in the original bioassay units together with the percentage by weight of active ingredient which may be ex fermenter material or an estimate of total crystal content.Because of the differences in individual toxins even Figure 2. The European corn borer (Ostrinia nubilalis) is the pest most dreaded by the maize grower; it eats its way right through the stalk of the maize plant. Photo courtesy of John Norris. Copyright Syngenta. INSECT CONTROL researchers and other experts find it harder than ever to interpret such data to predict field performance. Thus at present the only realistic unit of potency information for the end user may be the manufacturer’s recommended dosage for each individual pest pitted against the retail price of the product. Over the years the potency of products has been increased dramatically. Since 1959 the use of new strains has produced an increase of over 10-fold.Also in three decades kurstaki products have shown a 6-fold increase in stated label potency due to improved fermentation harvest formulation and application technology. The resultant 60- fold improvement – in reality probably more – has progressively enabled less product to be applied less frequently in the field at greatly reduced cost (Burges and Jones 1998a b). Search for improved Bt strains To increase the available toxin gene pool extensive strain search and assessment programmes were undertaken e.g. Martin and Travers (1989); Meadows et al. (1992); Bernhard et al. (1997). Primary assessment of strains was by bioassay later greatly improved by use of biochemical methods. By sequencing genes and recognising key toxin sequences PCR could be used to search for specific toxin genes.The method can investigate whether the potency exhibited by a new isolate is due to excessive toxin production by a known gene or whether the isolate might harbour a novel gene. For example Zhong et al. (2000) found the first gene known to be active albeit moderately so simultaneously in three insect orders Diptera Coleoptera and Lepidoptera. Some new strains are highly potent against difficult pests not well controlled by existing products and were developed into new products. Delta-endotoxin genes are carried mainly on plasmids exchangeable between strains by conjugation. The various combinations of toxin genes found in naturally occurring strains often do not confer optimal spectra of insect activity Figure 3.LEFT – Conventional maize attacked by the European corn borer larvae. RIGHT – Bt maize showing builtin protection to attack by European corn borer larvae. Photos courtesy of John Norris. Copyright Syngenta. 93 Pesticide Outlook – June 2001 INSECT CONTROL for the control of particular insect pests or pest complexes. By conjugation strains may be tailored to fit particular important pest complexes as exemplified by strain GC-91 (Jarrett and Burges 1986) which has been commercially developed and is sold under various trade names. It is a conjugant of two strains each containing desirable toxin genes and was found by selecting amongst the progeny of conjugation. This process is essentially the same as used in traditional plant breeding.Since it is a naturally occurring process its registration follows the same rules as for natural isolates. The same results could have been achieved of course by recombinant DNA technology but release of recombinant Bt strains into the environment was not permitted until recently. Transgenic plants producing toxins Each toxin protein is the product of a single gene that can be engineered into plants. Selected plants express the toxin systemically at levels sufficient to control susceptible insect pests while having only minor effects on crop yield. The genes are seed-transmitted and seeds of the best plants have been mass-produced for sale as insect resistant varieties – my daydream of the perfect systemic insecticide come true.At present only three crops engineered with Bt maize cotton and potato are grown commercially. Resistant varieties of at least 23 other plant species involving at least 10 toxin genes have been produced. The most favoured toxins are from ssp. kurstaki for control of a relatively wide spectrum of Lepidoptera pest species (Figures 2 and 3) and from ssp. morrisoni for control of the Colorado potato beetle. However because of the limited range of insecticidal activity exhibited by individual toxins the different species of Lepidoptera vary in susceptibility so some species may not be adequately controlled and others not controlled at all. For example in some early trials Heliothis virescens was well controlled but damaging populations of the less susceptible secondary pest H.zea survived. Thus local pest complexes must be assessed when deciding where to plant particular ‘insect resistant’ varieties. Luckily more than one toxin each with a different insecticidal range can be engineered into a single plant variety. The burgeoning planting of transgenic plants mostly with single genes and often in large areas of monoculture has suddenly vastly increased the spectre of resistance appearing in insects. Resistance to Bt No insect resistance has appeared yet to transgenic ‘Bt’ crops. Industry is very aware of the danger and many seed vendors insist on customer agreements to apply preventative measures. At present the favoured preventative method is planting a proportion of the crop area in refugia of nontransgenic varieties that would dilute out any resistance genes.This has been welcomed by farmers but possibly not all are applying it. A refuge can also be managed to favour biological control of other pests not controlled by the toxins e.g. aphids. Also plant varieties with more than one toxin gene (thus less likely to cause resistance) are just Pesticide Outlook – June 2001 94 beginning to become available. In 1971 I predicted that ‘Microbial control programmes should be studied in sufficient detail to reveal any resistance that may develop’ (Burges 1971). Resistance to kurstaki insecticides in the field has appeared in the diamond back moth in areas of intensive usage at first in Hawaii but now fairly wide ranging.Meanwhile it has been induced in laboratory populations of many moth species serially challenged with ssp. kurstaki. Resistance developed most quickly using strains modified to carry only one toxin gene. In contrast no mosquito species has become resistant to ssp. israelensis either in laboratory or field (Becker 2000). This subspecies has a distinct advantage over chemical insecticides used in water. These chemicals have induced resistance rapidly in mosquitoes and have also caused pest population resurgence. Resistance has probably been prevented so far in ssp. israelensis by the presence in its crystals of a multiple of five toxins. These include Cyt1A with a somewhat different mode of action to the Cry toxins and synergistic to them.Presumably the appearance of resistance events simultaneously to five toxins is far less likely than resistance events involving only one single toxin. The presence of a multiple of four toxins in ssp. kurstaki may explain the late appearance of resistance to products containing this subspecies in terrestrial pests. By far the most important mechanism by which an insect becomes resistant is change to the high affinity binding sites on the brush borders of gut epithelial cells i.e. sites that are recognised by particular toxins. Laboratory insect stocks bred for resistance to a toxin often have no or reduced binding capacity for that particular toxin (Schnepf et al. 1990). Safety Bt has a remarkably good safety record.When first registered as an insecticide ca. 1959 it was realised that tests were required for infectivity as well as for the usual toxicity demanded of chemicals so an extended range of safety tests was applied. This range was much more extensive than tests required for insect pathogens today and included infectivity/toxicity tests on human volunteers as well as allergy tests and tests for genetic stability (Fisher and Rosner 1959). In the four decades since then the ultimate test – practical usage – involved the application of thousands of tons of commercial products. Many tons were sprayed by air repeatedly over major cities in North America and New Zealand to eradicate imported moth pests; the exposed human populations were screened; every commercial product has been subjected to its own set of safety tests.Bt is regarded as one of the safest modern insecticides. Most of the safety data have been assembled and assessed by Glare and O’Callaghan (2000) and critically reviewed by Siegel (2001). There are some reports of isolation of industrial Bt strains from humans revealed by plating of samples. All except two have been cases attributed to soiling with dormant Bt spores. The first is a corneal ulcer developed by a farmer splashed in the face by the commercial kurstaki product Dipel. The second is a bacterial infection after an accidental self-injection in the hand of a researcher with a ssp. israelensis preparation contaminated by Acinetobacter calcoaceticus var.anitratus. In both cases growing vegetative Bt cells were not demonstrated in the lesion. The evidence for active infection by Bt itself is inconclusive because the Bt colonies on plates made from test samples could readily have grown from dormant inactive spores surviving in the lesion until the plating induced germination. Both cases were cured by antibiotic treatment. A wide variety of safety tests have been made on laboratory animals using most routes of application including the intracerebral route. Doses have been maximised and compared with high doses of other nonpathogenic bacteria. Unsurprisingly if enough spores were applied by very sensitive routes most species would kill or cause lesions so yardstick doses were elaborated.For example 106 spores with crystals of Bt injected intraperitoneally per mouse consistently caused no mortality the spores were rapidly eradicated from the mouse body. This contrasts with an LC50 of 3-8 spores/mouse of the virulent mammalian pathogen Bacillus anthracis. By the nasal/pulmonary route some mortality followed application of 108 spores of Bt per mouse but none after application of 107 spores which is equivalent weight for weight of 1011 spores applied to humans (Siegel 2001). Such an equivalent single harmless application is 100 million fold higher than the maximum cumulative exposure of spray operators or the general public in a city spray campaign (Elliott et al. 1988). It is also a thousand fold higher than the maximum exposure of a spray operator recorded for the entire spray season in field operational studies.Both exposure levels recorded in practice are less than proven safe levels by impressive margins. With transgenic plants infection is not a factor and the crystal toxin is not a poison in mammals. Allergy is unlikely as none of the toxins currently used commercially except one Cry 9C are affected by any of the six criteria used by the EPA to predict the possible potential of proteins to cause food allergies. A maize hybrid engineered with the Cry 9C toxin was registered only for use as animal feed simply because it was not destroyed by simulated human acid gastric fluid one of the EPA criteria for possible allergy. However this hybrid ran into practical trouble when some of the maize crop was illegally used in the production of taco shells and so entered the human food chain although no adverse effects were recorded.EPA purchased all known ‘contaminated’ food for resale as animal feed at the (costly) expense of the seed vendor. The hybrid was voluntarily withdrawn from the market. It must be emphasised that the perceived hazard was purely theoretical and probably very small i.e. just one of the EPA’s six indicator criteria was not met and no allergenicity tests had been performed. Thus in the present climate of public opinion pressure groups were powerful enough to force the EPA’s reaction. Some Bt strains produce exotoxins cyclodepsipeptides that can cause gastric and liver disorders in hens.From the 1960s a potential problem was avoided by banning exotoxin-producing strains by law from conventional Bt insecticides. Some but by no means all strains of B. cereus produce INSECT CONTROL enterotoxins and are implicated in mild food poisoning and some gut infections. As a result B. cereus has been classified as mildly (class 2) pathogenic to man while Bt is classified as non pathogenic (class 1). Recently inexpensive in vitro test kits to detect enterotoxins have been marketed. Using these kits with Bt strains researchers have shown that a surprisingly high proportion give a positive reaction among them the commercial strains. Products based on these strains have of course passed extensive in vivo testing as required for registration.Two facts point to a likely explanation of these apparently contradictory results. l Production of enterotoxin is favoured by richer media than those used in commerce. l These toxins are soluble in water and secreted during the vegetative growth phase after which sporulated cultures are concentrated by centrifugation removing the bulk of all soluble compounds. Thus enterotoxins are unlikely to be present at detectable levels in Bt products for sale. However if large numbers of spores were to enter moist food incorrectly kept warm for long periods they might germinate and produce these toxins. This could happen only if gross food-preparation malpractice is involved which is normally stamped out immediately by the food and health authorities.In these mal-conditions common food poisoning organisms or B. cereus are much more likely to intervene. Enterotoxins have not been considered a practical hazard of Bt except occasionally by some theorists out of touch with Bt ecology. Thus during the 40 years that industrial strains of Bt have been used for practical pest control the accumulation of knowledge has revealed few potential hazards. None has realistically impaired the excellent safety record of Bt. Among non-industrial subspecies of Bt konkukian was recently found in severe human wounds contaminated with soil in a land mine explosion. The wounds healed in 3 weeks after surgical cleansing and treatment with antibiotics (Hernandez et al. 1998). Another strain non-motile so it could not be serotyped was recovered from severe burns treated with water contaminated with the bacterium (Damgaard et al.1997). In both cases it was thought that infection was permitted by severe trauma impairing activity of the immune system. The mechanism is similar to occasional B. cereus infections in traumatised humans. These two Bt cases appear to be ecologically similar to B. cereus as possible sources of rare curable infections in exceptional circumstances. Dendrograms based on DNA genetic techniques may indicate possible genetic relationships within the Bacilli. Bt konkukian maps in a group containing most of the mammalian-pathogenic subgroup I Bacilli whereas the industrial Bt isolates map distant from this group (Paul J. Jackson personal communication).B. cereus and Bt do not have the specific toxins and cell capsule that make B. anthracis pathogenic in mammals nor are they likely to grow vegetatively and simultaneously in situations that would permit DNA exchange with B. anthracis to constitute a hazard. To eliminate the possibility of B. anthracis accidentally contaminating a product the original registrations 95 Pesticide Outlook – June 2001 INSECT CONTROL of Bt products required that samples of every fermenter batch are injected into mice as a routine mouse safety test. Due to its specificity Bt is very environmentally friendly (Glare and O’Callaghan 2000). It is a pathogen of insect herbivores and infects or poisons virtually no beneficial predators and parasites in fact the toxin has poisoned only one predator a lacewing (Schuler et al.2000). During successful pest control predators and parasites suffer a shortage of prey but this is an inevitable consequence of pest reduction by whatever means including chemical insecticides. Unlike chemicals Bt does not compound this effect by killing beneficial insects by direct poisoning. Bt does attack some non-target insect species closely related to pests including aquatic insects such as midges but because of its short persistence and poor spread it causes limited temporary collateral damage to non-targets only in treated areas. Crops genetically modified with Bt are even more environmentally friendly (Schuler 2000). Future The ‘wonder’ insecticide the crystal toxin has found a role in transgenic plants as the systemic active principle for a very safe group of insecticidal plants.Farmers’ adoption of transgenic plants in general in the past four years has been unprecedented (Figure 4). Future growth potential is several times greater than the current size of the whole crop protection chemical market. However an anti-transgenics lobby has successfully throttled public acceptance of food from transgenic crops. New epoch-making breakthroughs in technology e.g. the steam engine have typically attracted initial public suspicion and even violent opposition but they have survived. By the same token I believe that the present stranglehold will be temporary because transgenic plants are an economic success bringing great benefits to public health and prosperity also because many current objections and worries are not based on rational evidence.Industry must learn to inform the public about advantages and perceived problems in a clear palatable and attractive way. Extensive monoculture of transgenic plants makes insects potentially likely to become resistant to Bt. As already described industry is currently forcing farmers to take Figure 4. Use of Bt transgenic corn and cotton in the USA (1996-1999) Pesticide Outlook – June 2001 96 precautions against the development of resistance to Bt but in future these precautions must be reinforced by a variety of additional methods. Production of guidelines and international standards such as those for the chemical pesticides developed by the European Plant Protection Organisation EPPO would help risk evaluation and analysis.The design of transgenic plants is likely to be refined. Site specific promoters can be used e.g. wound induced expression of the toxin would reduce the risk of resistant insects and lessen the reduction of yield caused by foreign genes. Toxin expression can be increased partly by promoters like Prrm in tobacco chloroplasts which induce toxin totalling 5% of soluble plant protein compared with 0.01–0.6% resulting from constitutive promoters. Several toxin genes possibly including the gene for the Cyt1A toxin may be put into a single plant to lessen the risk of insect resistance. They can be augmented by factors against more groups of insects e.g.lectins proteinase inhibitors and chitinase production to widen the pest-control spectrum. More research will be applied to collateral effects on the environment and model guidelines have already been designed for testing and for selecting indicator species (Schuler et al. 2000). Integrated Pest Control Programmes (IPMs) are likely to increase. The international development banks are shifting their investment support in pest management from chemical control programmes to technologies like IPM. Bt toxins are an important component because they are so safe specific and environmentally friendly. Also Bt insecticide is being used as one of the alternatives to help reduce pest resistance to chemicals. Its ability to eradicate moth pests by overspray of centres of dense human population has been proved so this practice should become less controversial.Ssp. israelensis is well established and increasing for mosquito and blackfly control and spores can be killed by gamma irradiation without reducing efficacy for use in some countries that forbid adding spores to potentially potable water supplies e.g. Germany (Becker 2000). However several multinational companies have sold their Bt insecticide interests over the last five years. Hopefully a stronger more focused industry may emerge to service an erratically increasing demand. The search for new or better strains/toxins for use in insecticides and transgenic plants is gaining momentum. At present the best products involve ca.2.5 g/ha of toxin in the most favourable applications. The target for new toxin combinations should approach the 0.5 g/ha active ingredient target for the development of new chemical insecticides. There is still scope for formulation improvement. On land phagostimulants may be used more. Greater sophistication tends to increase cost which must be balanced against both improved efficacy and reduction in the frequency of applications. For ultra low and low volume sprays rather than increasing additives in on-shelf products the additives should be put into the tank mixes and used only for those crops for which the extra cost is justified. For high volume microgranules/capsules allow economy of many types of additives by keeping them in juxtaposition to the active ingredient where they function best.Capsular protection can be maintained by delaying release of the toxin until it reaches the insect gut by using pH as a release trigger. The ratio of field studies to laboratory work has ebbed and flowed this is likely to continue. At present research emphasis is on microbiology genetics and ecology. This may continue for some time. Knowledge about mode of toxin action and causes of resistance should increase. Thus knowledge of Bt and the B. cereus group of spore-forming bacteria forms a fascinating and rapidly expanding segment of the science of bacteriology featuring ecology toxins and genetics in particular. On the practical insect control front Bt should continue to be the leading and pioneering microbial control agent by a very wide margin.References Becker N.(2000). Bacterial control of dipterans – general strategy and further development. In Proceedings of the 13th European Society for Vector Biology Meeting (S. S. Caglar B. Alten and N. Ozer eds) pp. 63–70. DTP Ankara. Bernhard K.; Jarrett P.; Meadows M.; Butt J.; Ellis D. J.; Roberts G. M.; Pauli S.; Rodgers P.; Burges H. D. (1997). Natural isolates of Bacillus thuringiensis worldwide distribution characterisation and activity against insect pests. Journal of Invertebrate Pathology 70 59–68. Bernhard K.; Utz R. (1993). Production of Bacillus thuringiensis insecticides for experimental and commercial uses. In Bacillus thuringiensis an Environmental Biopesticide Theory and Practice (P.F. Entwistle J. S. Cory M. J. Bailey and S. Higgs eds) pp. 255-267. John Wiley Chichester. Burges H. D. 1967a. Standardization of Bacillus thuringiensis products homology of the standard. Nature (London) 215(5101) 664–665. Burges H. D. 1967b. The standardization of products based on Bacillus thuringiensis. Proceedings of the International Colloquium of Insect Pathology and Microbial Control Wageningen 1966 306–314. Burges H. D. 1971. Possibilities of pest resistance to microbial control agents. In Microbial Control of Insects and Mites (H. D. Burges and N. W. Hussey eds.) pp. 445. Academic Press London. Burges H. D.; Jones K. A. (1998a). Formulation of bacteria viruses and Protozoa to control insects.In Formulation of Microbial Biopesticides Beneficial Microorganisms Nematodes and Seed Treatments (H. D. Burges ed.) pp. 33–127. Kluwer Academic Publishers Dordrecht. Burges H. D.; Jones K. A. (1998b). Trends in formulation of microorganisms and future research requirements. In Formulation of Microbial Biopesticides Beneficial Microorganisms Nematodes and Seed Treatments (H. D. Burges ed.) pp. 311–332. Kluwer Academic Publishers Dordrecht. Crickmore N.; Zeigler D. R.; Feitelson J.; Schnepf E.; Van Rie J.; Lereclus D.; Baum J.; Dean D. H. (1998). Revision of the nomenclature for the Bacillus thuringiensis pesticidal crystal proteins. Microbiology and Molecular Biology Reviews 62(3) 807–813. Damgaard P. H.; Granum P. E. R.; Bresciani J.; Torregrossa M.V.; Eilengerg J.; Valentino L. (1997). Characterization of Bacillus thuringiensis isolated from infections in burn wounds. FEMS Immunological and Medical Microbiology 18 47–53. INSECT CONTROL Elliott L. J.; Sokolow R.; Heumann M.; Elefant S. L. (1988). An exposure characterization of a large scale application of a biological insecticide Bacillus thuringiensis. Applied Industrial Hygiene 3 119–122. Fisher R.; Rosner L. (1959). Toxicology of the microbial insecticide Thuricide. Journal of Agriculture and Food Chemistry 7 686–688. Glare T. R.; O’Callaghan M. (2000). Bacillus thuringiensis Biology Ecology and Safety. Wiley Chichester. 350 pp. Hernandez E.; Ramisse F.; Ducoureau J. P.; Cruel T.; Cavallo J. D. (1998). Bacillus thuringiensis subsp.konkukian (Serotype H34) superinfection Case report and experimental evidence of pathogenicity in immunosuppressed mice. Journal of Clinical Microbiology 36 2138–2139. Jarrett P.; Burges H. D. (1986). Bacillus thuringiensis tailoring the strain to fit the pest complex on the crop. BCPC Monograph No. 34. Biotechnology and Crop Improvement and Protection 259–264. Jones K. A.; Burges H. D. (1998). Technology of formulation and application. In Formulation of Microbial Biopesticides Beneficial Microorganisms Nematodes and Seed Treatments (H. D. Burges Ed.) pp. 7–30. Kluwer Academic Publishers Dordrecht The Netherlands. de Maagd R. A.; Bravo A.; Crickmore N. (2001) How Bacillus thuringiensis has evolved specific toxins to colonise the insect world.Trends in Genetics 17(4) 193–199. Martin P. A. W.; Travers R. S. (1989). Worldwide abundance and distribution of Bacillus thuringiensis isolates. Applied and Environmental Microbiology 55 2437–2442. Meadows M. P.; Ellis D. J.; Butt J.; Jarrett P.; Burges H. D. (1992). Distribution frequency and diversity of Bacillus thuringiensis in an animal feed mill. Applied and Environmental Microbiology 58(4) 1344–1350. Ohba M.; Wasano N.; Mizuki E. (2000). Bacillus thuringiensis soil populations naturally occurring in the Ryukyus a subtropic region of Japan. Microbiological Research 155(1) 17–22. Schnepf H. E.; Tomczak K.; Ortega J. P.; Whiteley H. R. (1990). Specificity-determining regions of a lepidopteran-specific insecticidal protein produced by Bacillus thuringiensis.Journal of Biological Chemistry 265 20923–20930. Schuler T.H. (2000). The impact of insect resistant GM crops on populations of natural enemies. Antenna. Bulletin of the Royal Entomological Society 24(2) 59–65. Schuler T. H.; Poppy G. M.; Denholm I. (2000). Recommendations for assessing affects of GM crops on non-target organisms. Proceedings of the Brighton Crop Protection Conference – Pests and Diseases 3 1221-1229. Siegel J. P. (2001). The mammalian safety of Bacillus thuringiensis-based insecticides. Journal of Invertebrate Pathology 77 13–21. Smith R. A.; Couche G. A. (1991). The phylloplane as a source of Bacillus thuringiensis variants. Applied and Environmental Microbiology 57 311–315.Steinhaus E. A. (1951). Possible use of Bacillus thuringiensis as an aid in the biological control of the alfalfa caterpillar. Hilgardia 20 359–381. Vaid A.; Bishop A. H. (2000). Whole-cell PCR of Bacillus thuringiensis recovered from the phylloplane. Journal of Invertebrate Pathology 76 147–148. Zhong C.; Ellar D. J.; Bishop A.; Johnson C.; Lin S.; Hart E. R. (2000). Characterization of a Bacillus thuringiensis d-endotoxin which is toxic to insects in three orders. Journal of Invertebrate Pathology 76 131–139. 97 Pesticide Outlook – June 2001 INSECT CONTROL H Denis Burges joined the Pest Infestation Control Laboratory UK in 1944. His first 16 years of research involved the biology of stored products’ pests as background information for the design of nonchemical pest control measures.Specifically this led to the quarantine of one pest species modification of buildings to eliminate another and the adoption of in store cooling of grain bulks by controlled aeration to prevent the development of the complex of grain pests. By 1958 study of straight insect biology was palling and he turned to study of pest control by insect pathogens mainly Bacillus thuringiensis stimulated by an outbreak of disease in his insects. In 1970 a move to the Glasshouse Crops Research Institute switched these studies to GHENT CONFERENCE 2001 Nearly 500 delegates attended the 53rd Ghent Conference heldon 8 May 2001. The conferences started with two plenary lectures followed by 60 oral presentations and 91 posters.Plenary lecture 1 – Potato blight Francine Govers associate professor at Wageningen University The Netherlands is doing pioneering work into the molecular genetics of late blight Phytophthara infestans. She said that since 1980 there had been a re-emergence of late blight problems primarily because of the emergence of a sexual mating form of P infestans which can overwinter as a hardy oospore as well as the vegetative form which remains in infected tubers. From 1994-1996 the research team led by Professor Govers characterised 2000 isolates of the organism and found at least 170 different genotypes. Progress in sequencing the genes in P. infestans has been slow but is improving. By 1997 eight genes had been sequenced and 11 by 1998 for inclusion in a public database (www.ncgr.org/pgc).By 1999 this figure had jumped to 770 as work focused on genes being expressed in the organism. More genes show homology to plant genes that to fungal genes. About 30% of the genes sequenced so far show no homology with any genomes in public databases. These may be unique to oomycetes and may be related to pathogenesis. Pesticide Outlook – June 2001 98 glasshouse pests integrating pathogens into biological systems already in place. By the 1960s Denis became interested in the broader issues that faced the use of insect pathogens and he became involved in the international scene largely through the World Health Organisation colleagues met during a Sabbatical Year spent in the USA and the Society for Invertebrate Pathology of which he became a President. The most important of these international activities involved pathogen safety and standardisation of potency measurement and expression. He produced three major books (1971 1981 and 1998) and published 152 research papers and reviews over the years. Plenary lecture 2 – Pesticides in field vegetables The other plenary lecture was given by Stan Finch of Horticulture Research International Wellesbourne UK who tackled the question of whether the world could cope without synthetic pesticides in field vegetables. He was forced to conclude that it could not. He commented that much progress had been made to reduce pesticide consumption especially with the use of insecticide film coatings on seed. Chlorfenvinphos rates could be cut from 2500 g ai/ha in the field to 100-200 g ai in modules and 2g ai/ha in film coats. Whilst control without chemicals is easier in carrots as there are only three main pests in the UK brassicas present much greater problems with 49 insect pests. Adult cabbage root flies are particularly problematical as no pesticides seem able to control them although they can control the larval forms. One of the problems in the UK has been the cultivation of oilseed rape which creates waves of cabbage root fly late in the season in the summer which are very hard to control. Vegetables are also “outside the profit tent” for pesticide companies. See http://allserv.rug.ac.be/~hvanbost/symposium/ for further details. Brian Hicks Crop Protection Monthly

ISSN:0956-1250    

DOI:10.1039/b104591c

出版商:RSC    

年代:2001

数据来源: RSC

摘要:

The concept of crop adapted spraying For an efficient use of pesticides targeted against diseases and pests which attack green plant parts and fruit a certain amount of active ingredient must be deposited per unit leaf area of the target plant. Measurements in commercial berry crops in various parts of Switzerland over the last 3 years have shown that the leaf area of strawberries raspberries blackberries and red currants increase by a factor of 8–12 from the early stages of growth till fruit maturing (Figure 1). This marked increase in leaf area implies that the dosage of the products would need to follow for practical reasons a stepwise increase approximately matching the increase of the leaf area. This concept of adapting the product dosage to the growing leaf area of a given crop coupled to the application of the product with a well-calibrated sprayer properly adjusted to reach all parts of the leaf canopy of the specific crop can be termed Crop Adapted Spraying (CAS).Commonly labels on crop protection products only state a certain amount of product in kilograms or litres to be used per hectare. It is left to the grower whether and how to adapt the dosage of the product to the growing crop. Onfarm observations have shown clearly that most growers are uncertain about what amount of product in which volume of water they should use at a given growth stage. Often products are grossly under- or overdosed and spray equipment is not or is poorly calibrated and adjusted to the specific crop. Thus our primary goal for developing CAS in berry crops was to provide growers with a guideline on how to use fungicides insecticides and acaricides more efficiently and economically.Testing the concept As a result of three years of intensive on farm research easyto-follow tables for crop adapted product use were devised for major berry crops. These tables state for four major consecutive growth stages the amount of the single strength spray volume the grower should apply with a properly calibrated sprayer. Most pesticides for legal use on berry crops in Switzerland have been tested and registered with a single strength concentration in a basic water volume of 1000 litres per hectare. The majority of growers apply spray broths of single strength.With stepwise increasing single strength spray broth volumes the tables provide an automatic increase of the amount of the product and active ingredient applied. The concept of CAS has been tested so far in a series of on farm experiments using properly calibrated and crop adjusted on farm spray equipment. DOI 10.1039/b104686c TOWARDS CROP ADAPTED SPRAYING (CAS) IN BERRY CROPS economical uses of pesticides Jacob Ruegg and Helena Bak of the Swiss Federal Research Station for Fruit Growing Viticulture and Horticulture at Wädenswil in Switzerland describe a simple spraying concept aimed at more efficient and Experimental results have shown that compared to farmers’ traditional spray practices CAS allowed to save between 30 to 50% of the amount and costs of crop protection products with equal or better biological efficacy and usually lower residues on harvested berries.While farmers usually sprayed clearly beyond run-off spraying in our experiments was always carried out without or with minimum run-off. This journal is © The Royal Society of Chemistry 2001 Pesticide Outlook – June 2001 Outlook For the forthcoming season 2001 we have organised four CAS-technology training courses for approximately 140 farmers in four distinct regions of German-speaking Switzerland. The implementation of CAS by selected key farmers will be followed up and evaluated. The emphasis will be on biological efficacy of the products sprayed savings in overall product use and residues on fruit at harvest time.Modifications to suit local conditions and preferences such as the application of reduced water volumes with multiple strength spray broths need to be tested and discussed with the industry. Implications of CAS for the registration of crop protection products in berry crops will be discussed within the registration authorities and with the industry as well. We believe that the CAStechnology has benefits to offer to the growers the environment and the end consumers. On farm evaluation of CAS in the next couple of years will reveal the practicality and viability of this crop tailored dosage and application of crop protection products in berry crops. Further work has been initiated to develop CAS also for selected vegetable crops such as tomatoes potatoes bushbeans and carrots. Figure 1. Total leaf and stem area and volume per ha of an Elsanta strawberry crop (Switzerland 2000) (6.7 plants per m2). The leaf area measured with an electronic leaf area meter was computed based on a sample of 5 harvested plants at each sampling date. The volume of the crop was computed based on crop height � crop width � length of crop rows. APPLICATIO

ISSN:0956-1250    

DOI:10.1039/b104686c

出版商:RSC    

年代:2001

数据来源: RSC

摘要:

APPLICATION density. MATCHING SPRAY APPLICATIONS TO CANOPY CHARACTERISTICS IN CEREAL CROPS Paul Miller Andrew Lane and Helen Wheeler from Silsoe Research Institute Wrest Park Silsoe Bedford MK 45 4HS UK describes a “precision farming” approach such materials by matching the characteristics of a delivered spray to those of the target crop canopy. The simplest form of such a relationship may be to adjust the volume application rate of a given tank mix of chemicals to the local value of leaf area or vegetative index in given parts of a field. However considerable research and practical development has been directed at defining other physical characteristics of a spray that influence both retention and efficacy of an application including droplet size distribution trajectory angle of the spray velocities of droplets within the spray and air conditions associated with the spray delivery.It may therefore be appropriate to adjust other factors controlling spray delivery to improve performance in given crop canopy conditions. The work described here has the main objective of linking spray applications to crop canopy characteristics so as to make recommendations relating to the improved use of fungicides and similar chemical sprays. 100 or 200 l/ha fine or medium vertical or 45° backwards The potential advantages There is now substantial evidence to indicate that in many arable crop situations improvements in both the financial and environmental aspects of crop production could be achieved by the appropriate management of spatial variability.The development of such “Precision Farming” approaches has been made potentially viable by technological developments relating to l field-scale location systems where the development of methods based on optical reflectance radio systems and most significantly satellite navigation (e.g. the Global Positioning System) has enabled location to be determined to typically better than ±2.0 m at an acceptable cost; l robust and relatively low cost computer systems for data collection manipulation and control that can be incorporated into or mounted along side existing systems used with field-based agricultural equipment; l appropriate sensor systems that enable a range of physical parameters to be measured such as the grain flow rate into the tank on a combine harvester for yield mapping or soil electromagnetic inductance to show differences in structure composition and moisture holding capacity across a field.For plant protection products such as fungicides that have a mode of action that is primarily associated with the surface of leaves then there may be scope to optimise the use of Figure 1. Map showing vegetative index measured in the winter wheat crop and divided into areas of high and low crop canopy 100 Pesticide Outlook – June 2001 This journal is © The Royal Society of Chemistry 2001 Field studies Experiments were conducted on two fields in crops of spring and winter wheat using spectral reflectance measurements as a measure of crop canopy density.Measurements of vegetative index across each field were made using radiometers mounted on a spray boom at a spacing of approximately 4 m and a height of 1.5 m above the crop. An arrangement for recording the output from the radiometers into a portable computer was devised such that vegetative index could be calculated and tagged with position in the field from a GPS system also connected to the computer. By driving along tramlines at a speed of about 10 km/h before the crop had reached growth stage 32 data from which a vegetation index map could be plotted was obtained. The contours between areas of different vegetative index were smoothed in a computer mapping program and the field area was then divided into approximately two equal areas on the basis of the measured vegetative index (see Figure 1).Application plots were then laid out randomly in both areas of high and low crop canopy density. Randomised replicated plots each 10 m by 20 m were laid out to enable the following application variables to be investigated l spray volume rate l spray quality l angle of delivery Applications were made are both growth stage 32 and 39. DOI 10.1039/b104594f Results The measured spray deposits for the main treatment effects are shown in Figure 2. The differences in deposit level between areas of high and low crop canopy density are small. It was expected that deposit levels per unit of plant weight would be higher where the crop density was lower but this was not the case (Figure 2a).The results however did show some important and expected trends namely:- l spray deposits tended to increase when using a fine rather than a medium quality spray (Figure 2b) with the largest increase at the earlier growth stage l using the lower volume application rate (100 l/ha) gave substantially higher deposits than the conventional volume rate (200 l/ha) again with the largest difference at the earlier growth stage (Figure 2c) l angling the delivery of the spray also increased the level of deposit at the earlier growth stage as expected (Figure 2d) Figure 2 Spray deposits for different treatments. (a) The effect of canopy density (b) The effect of spray quality (c) The effect of volume application rate APPLICATION l penetration into the canopy was much greater for the smaller canopy condition at the earlier growth stage (Figure 2e) l It is very noticeable that deposit levels per unit of plant weight are consistently higher at the earlier growth stage.This reflects the changes in canopy size between the two growth stages and the fact that no changes were made to the application to account for this increasing canopy size Whereas Figure 2 gives the mean deposit levels for the main treatment effects a statistical analysis of the results indicates that the interactions between the experimental variables may be important. This is to be expected since for example it is likely that angling the spray delivery will have a larger effect on deposition when treating a relatively low canopy density at an early stage of growth compared with a more dense and well established canopy condition.(d) The effect of angled delivery (e) The penetration of spray into the canopy at the two growth stages Pesticide Outlook – June 2001 101 APPLICATION Implications from the results Although the differences between deposit levels in the areas of high and low canopy density within a given field were small differences between the two growth stages were consistent and much larger. This result suggests that there is scope to improve application performance by matching spray delivery parameters to crop canopy structure and that changes should initially account for the effects of growth stage. Any strategy that aims at matching spray application to crop canopy structure requires a robust method of defining the canopy characteristics.Methods based on spectral reflectance measurements are being developed commercially to control the application of nitrogen fertilisers and are likely to be effective at early stages of growth but less discriminatory when the canopy is fully developed. The approach taken in the work reported here was to sense canopy characteristics at an early stage of growth when there was a high level of confidence in the sensor system being able to discriminate between differences in different parts of a field. However this strategy has an important weakness in that changes in canopy structure between sensing and treatment may be important and are not accounted for.Improved methods of sensing canopy structure may therefore be required. One approach that could be used to account for crop growth stage could be the use of growth rate keys with established relationships between the canopy and defined growth stage for the major cereal and/or oilseed varieties. Such an approach could then be implemented easily and at a relatively low cost. The results attained in the work are also dependent upon the fields used for the study. Although there was variation in these fields more information is needed on the range of variation in crop canopy conditions across a field. It is possible that larger variations in soil type aspect or drainage will give larger differences in canopy structure then those observed in this work and that the scope for spatially varying application parameters is greater.SILSOE RESEARCH INSTITUTE (SRI) SRI is the only research centre in the UK dedicated to the application of engineering and physical sciences to a wide range of biological systems and processes including applications in the food processing industry. SRI’s remit was to develop the mechanisation of UK agriculture but over the last 20 years there has been a strong move towards topics with a process engineering modelling and optimisation or environmental objective. Science groups l Environment l Biomaterials Group l Livestock Engineering l Mathematics & Decision Systems l Soil Science l Image Analysis l Chemical Applications l Heat & Mass Flow l International Development l Robotics & Automation Of particular interest to readers of Pesticide Outlook will be the Chemical Applications Group which has extensive experience of research on pesticide application systems and how the behaviour of sprays from nozzle to target influences losses to drift.For further information Silsoe Research Institute Wrest Park Silsoe Bedford MK45 4HS UK. (http://www.sri.bbsrc.ac.uk) 102 Pesticide Outlook – June 2001 This study shows the importance and potential for adjusting a number of parameters defining spray application other than volume and/or dose rates. The ability to adjust volume rate spray quality and the delivery angle of sprays is likely to provide opportunities for increased deposition improved targeting within the canopy and optimised pesticide use.Acknowledgements The main part of the project work was funded by the Home- Grown Cereals Authority The Ministry of Agriculture Fisheries and Food funded aspects of the original work on sensing crop canopy characteristics. Thanks are also due to colleagues from Silsoe Research Institute Tom Robinson (Novartis Crop Protection Ltd) and Ben Freer (Morley Research Centre). References Miller P. C. H; Lane A. G; Wheeler H. C. (2000) Matching the application of fungicides to crop canopy characteristics. Proceedings The BCPC Conference – Pests and Diseases 629–636. Miller P. C. H; Paice M. E. R. (1998) Patch spraying approaches to optimise the use of herbicides applied to arable crops. Journal of the Royal Agricultural Society of England 159 70–81. Paul Miller is an agricultural engineering graduate who joined what is now Silsoe Research Institute in 1971 and following research work relating to the sugar beet crop and grain drying was appointed to lead the Chemical Application Group in 1984. His research interests cover most aspects of agricultural chemical application particularly spray drift nozzle performance and sprayer control. In 2000 Paul was appointed to the post of Project Director and Head of Process Engineering Division that includes the Chemical Application Group. He is a Visiting Professor of Cranfield University and a Senior Research Fellow with the Home-Grown Cereals Authority with interests relating to precision farming approaches.

ISSN:0956-1250    

DOI:10.1039/b104594f

出版商:RSC    

年代:2001

数据来源: RSC

摘要:

Introduction The diseases caused by fungi that affect stem bases of cereals in the UK and much of continental Europe are eyespot the most important of them (Figure 1) caused by Tapesia yallundae and T. acuformis; sharp eyespot caused by Rhizoctonia cerealis; and brown (fusarium) foot rot (Figure 2) caused by Fusarium spp. and Microdochium nivale. The brown foot rot fungi also cause ear blight and can be seedborne. M. nivale can decrease plant emergence and also cause snow mould a serious disease of over-wintering cereals in northern latitudes. This group as a whole therefore has complex epidemiology that presents difficulties in control and in the choice of measures to achieve it. Fungicides as discussed by Leroux (1998) have been widely used for about 30 years specifically to control eyespot.Some recent reports (Burnett 2000; Nicholson and Turner 2000) however have inferred from field experiments that applying fungicides even highly active ones such as cyprodinil has often not been cost-effective. This paper examines by reference to recent research the reasons for this and the prospects for the situation continuing. It also considers new research that may contribute to more cost-effective environmentally sound disease management using an integrated approach. BIOLOGY AND CONTROL OF STEM-BASE DISEASES OF CEREALS IN THE UK disease management Geoff Bateman and John Jenkyn from IACR-Rothamsted examine the reasons that application of fungicides to control cereal stem-base diseases may often not be cost-effective and consider the prospects for integrated This journal is © The Royal Society of Chemistry 2001 Pesticide Outlook – June 2001 103 and in recent years has not always been considered by farmers as a major disease.This is despite estimates from official surveys that yield losses in England and Wales amounted to £16 million in 1999 the 10-year average being £17 million (N. Hardwick personal communication). Estimated losses in 2000 were the largest for 25 years at up to £22 million at current grain prices. This confirms eyespot’s significance and should not deter the development of new fungicides research on alternative control practices or integration of eyespot control into overall disease management strategies. Eyespot was relatively unimportant in the 1960s mainly because of effective resistance in Cappelle-Desprez and wheat cultivars derived from it.It was maintained at low levels subsequently by fungicides particularly the MBC group (benzimidazoles and thiophanates) and host resistance became less important. The benzimidazoles were largely replaced by other fungicides such as prochloraz when MBC-resistance developed in the 1980s and led to increased crop losses. Eyespot was then a research priority and much valuable epidemiological work was done (e.g. Goulds and Fitt 1991). In many recent field trials fungicides applied to control eyespot have often failed to increase yields significantly (Bateman et al. 2000; Burnett et al. 2000; Nicholson and Turner 2000).The small effects on yields in many individual trials suggest that the large total losses estimated from national survey data may be mainly a consequence of modest losses in many fields rather than more variable and sometimes large losses. Figure 2. Severe brown foot rot on wheat stems caused by Fusarium culmorum Changing importance and perceived significance in the UK Eyespot has fluctuated in importance as a target for control Figure 1. An eyespot-infected wheat crop showing severe lodging in 2000 a year in which the disease flourished in the UK. DOI 10.1039/b104740j DISEASE CONTROL DISEASE CONTROL Table 1. Putative factors affecting population changes in Tapesia spp. Suggested effect Factor Assessment MBCs and DMIs select for T.acuformis Fungicides Barley rather than wheat selects for T. acuformis Crop Late drilling favours T. yallundae Sowing date Weather Various e.g. spring frost delays T. acuformis Sharp eyespot can cause yield losses in localised patches within crops but has never been considered a major problem. Losses in the UK have never been great (estimated in England and Wales at £4 million in 1999 with a 10-year average of £3 million N. Hardwick personal communication) despite the absence of effective fungicidal control. The contribution of Fusarium species to stem-base disease has long been recognised but it came to prominence in the 1990s when research proliferated as concern about eyespot was declining. Losses are unlikely to be large. The main threat from Fusarium is ear blight for which stem-base disease may be an important inoculum source.So far mycotoxins that can occur in Fusarium-infected grain are at a low level in the UK but that situation could change if the climate changes. Eyespot pathogen populations and their significance The fast- and slow-growing pathogenic types of the eyespot fungus formerly referred to as W-type and R-type of Pseudocercosporella herpotrichoides have the teleomorph (sexual) stages Tapesia yallundae and T. acuformis. Fruiting bodies of T. yallundae (Figure 3) occur naturally on infested over-wintering stubble but those of T. acuformis are rare in the field. Most epidemiological research on eyespot has concerned epidemics arising from conidia asexual spores dispersed mostly over short distances by rain-splash.The fairly recent evidence for the production of air-borne ascospores has added a new dimension to the epidemiology Figure 3. Apothecia of the eyespot fungus Tapesia yallundae on a piece of barley stem. (Photo P.S. Dyer) 104 Pesticide Outlook – June 2001 Not proven for MBCs; good evidence for DMIs Good experimental evidence Good evidence from epidemiological research Some evidence but likely to be important only in individual crops of eyespot especially as they develop readily in uncultivated set-aside fields but their full significance has not yet been determined. Differences in the epidemiology of the two Tapesia spp. arise mainly from their different rates of development following infection.Tapesia yallundae develops more quickly and so is often found earlier in crops (Goulds and Fitt 1991). Weather can influence these differences for example it was thought that a cold winter caused loss of basal leaf sheaths that prevented further development of T. acuformis that had not yet penetrated them (Goulds and Fitt 1991). Both species of eyespot fungi can cause severe disease in wheat crops by the end of the growing season (Goulds and Fitt 1991). However the slower development of T. acuformis means that it is less likely to become severe. This was demonstrated in several field experiments but results from an experiment in which plots were inoculated with different amounts of the two fungi showed that symptoms of similar severity caused by the two pathogens were similarly damaging (Figure 4; Bateman and Jenkyn 2000).During the 1980s it became apparent that populations of the eyespot fungus in the UK generally changed from being predominantly the fast-growing type (T. yallundae) to predominantly the slow-growing type (T. acuformis) (King and Griffin 1985). A recent survey suggests that T. acuformis still predominates in UK populations (West et al. 1998). It was more frequent in wheat crops in Scotland and northern England than in the south. Putative causes and significance of population changes are discussed in the following sections and are listed in Table 1. Fungicides have undoubtedly been important in selecting Tapesia spp. MBC fungicides were implicated in the dramatic change to a predominance of T.acuformis which occurred along with resistance to these fungicides (King and Griffin 1985) but this was not proven experimentally (Bateman et al. 1990). Long-term experimentation suggested that this selection can occur as a result of using DMI fungicides such as prochloraz (e.g. Bateman et al. 1995). These fungicides were not used against eyespot in the early 1980s but their use against foliar diseases may possibly have affected the eyespot pathogens. Resistance to prochloraz has been found particularly in France but its significance there and in the UK is unclear. Repeated application to the same wheat plots at Rothamsted since 1984 has resulted in pathogen populations that are almost entirely T.acuformis because of its greater range of sensitivi-Table 2. Present and prospective management options for cereal stem-base diseases Problems and practicality Potential value Management option Stem-base diseases not a breeding priority Very good Host resistance Effects of break crops variable. Economics may favour intensive cereal growing Moderate Crop sequence Late sowing can reduce potential yield and often presents practical difficulties Good Late sowing Ploughing and non-inversion tillage affect different diseases differently Variable Cultivation Risk assessment not always reliable; over-use can lead to resistance; expensive Good Fungicide Excessive straw residues on the surface can affect drilling and crop establishment Variable Straw management Not known Biological control Effective treatments not available ties (Bateman et al.1995) but tests for resistance to prochloraz proved negative. Prochloraz-treated plots have often yielded most but the effects were never significant. This may be a consequence of the pathogen population having a large proportion even in untreated plots of the slower-developing T. acuformis. This suggests that the widespread use of prochloraz whilst not always controlling eyespot may have decreased losses and potential losses caused by eyespot by maintaining T. acuformis as the predominant fungus. Increased barley growing was suggested as a possible contributory cause of the change to predominantly T. acuformis after 1980. It was demonstrated subsequently that barley selects for populations with greater proportions of T.acuformis than does wheat (Bateman and Gutteridge 1996). The proportion of T. acuformis in wheat is greater in Scotland where barley constitutes a greater proportion of the cereal acreage than in southern England (West et al. 1998). This appears to be consistent with the experimental evidence although evidence from crop sequences sampled in Figure 4. Effect of eyespot severity on grain yield of winter wheat. Data for both eyespot fungi Tapesia yallundae (solid circles) and T. acuformis (open circles) fit a single regression line. This indicates that although the latter usually produces less severe disease similar amounts of disease caused by the two fungi are expected to have similar effects on yield.the survey (West et al. 1998) was less convincing. Where a large proportion of the cereal acreage is barley selection for T. acuformis may contribute to decreased potential losses in wheat crops. Husbandry practices may affect the two eyespot pathogens differently because of differences in their epidemiology. Earlier sowing of winter cereals is likely to be the main factor. Greater proportions of T. acuformis were found in earlier drilled wheat crops (West et al. 1998) which allowed more time for the slow-developing R-type epidemics to become severe. The longer growing season in more northerly latitudes may also favour T. acuformis. DISEASE CONTROL Biological interactions It is well known that there is often an inverse relationship between eyespot and sharp eyespot and that fungicides active against eyespot can increase sharp eyespot.The strobilurin fungicide azoxystrobin can decrease sharp eyespot if included in a stem-base treatment but the benefit from this effect is likely to be small. Eyespot and sharp eyespot were often more severe after ploughing than after non-inversion tillage but ploughing usually decreased fusarium foot rot (Prew et al. 1995). Straw management also affected eyespot and sharp eyespot both of which were typically more severe where straw was burnt despite depletion of inoculum sources than where it was incorporated. Incorporating straw decreased these diseases only with non-inversion tillage. Brown foot rot tended to be increased by incorporating straw.However in a year with favourable conditions for foot rot caused by F. culmorum (i.e. warm and dry in early summer) this disease was less severe after straw incorporation than after burning despite more propagules of the fungus in the soil after straw incorporation (Bateman et al. 1998). The mechanisms are unclear and the effects are variable although suppression by straw is easily demonstrated in glasshouse experiments (Bateman unpublished). Inoculum sources and targets for control A severe outbreak of eyespot in wheat grown after ploughing following a long period of non-inversion tillage Pesticide Outlook – June 2001 105 DISEASE CONTROL during which buried inoculum was not expected to have survived up to its return to the surface by ploughing provided indirect evidence for the importance of ascospore inoculum (Jenkyn and Gutteridge unpublished).On the other hand the continued prevalence of T. acuformis not known to produce ascospores commonly in the field suggests that the widespread production of T. yallundae ascospores particularly in set-aside fields has had little general impact. Infected straw is an important source of primary inoculum for stem-base diseases but as indicated above straw can also have other effects. Straw management would therefore seem to offer prospects for contributing to the control of these diseases. In particular it may be possible to exploit the disease-suppressive properties of straw whilst managing it in such a way as to minimise its role as an inoculum source.Eyespot fungi are poor colonisers of straw but can survive up to 3 years when buried. Fusarium culmorum is a more effective straw coloniser and populations can build up very rapidly. Infected straw is therefore a less clear target for control of this fungus than for control of eyespot. Fungicides are unlikely to provide adequate control of rapidly developing brown foot rot unless they can be applied later in the season than is normal for eyespot but only a small proportion of chemical applied at a later growth stage using conventional spray equipment usually reaches the stem base. Later applications would have additional perhaps greater value in protecting ears from inoculum originating from stem bases.Discussion and conclusions The evidence suggests that applying fungicides to control eyespot may often have small and statistically nonsignificant (in experiments) effects in individual fields. Widespread small effects appear sometimes to explain the relatively large estimated losses on a national basis. For the individual farmer the economic case for controlling eyespot may often therefore be doubtful and a fungicide that controls leaf diseases as well as eyespot might be easier to justify. Relatively small effects on yield are likely to result from the prevalence of the pathogen T. acuformis which may be being sustained by the use of DMI fungicides that are less effective against this species than against T. yallundae. Since the effectiveness of fungicides can not be assured additional control measures based on husbandry that may also be effective against other minor stem-base diseases should be implemented wherever possible.Cropdebris management may be a useful component of this integrated approach but further research is needed so that the effects seen in some experiments can be exploited in a consistent and effective way. Table 2 summarises some of the current and prospective options that might be considered as components in an integrated management system for stem-base diseases. Acknowledgement We thank the British Crop Protection Council for permission to reproduce parts of a contribution to the BCPC 106 Pesticide Outlook – June 2001 Conference – Pests & Diseases 2000 (Bateman and Jenkyn 2000) from which this paper is adapted.References Bateman G. L.; Edwards S. G.; Marshall J.; Morgan L. W.; Nicholson P.; Nuttall M.; Parry D. W.; Turner A. S. (2000) Diagnosis forecasting risk assessment and control of stem-base diseases of wheat using new molecular technologies. HGCA Project Report No. 216 145 pp. Bateman G. L.; Fitt B. D. L.; Creighton N. F.; Hollomon D. W. (1990a) Changes in populations of Pseudocercosporella herpotrichoides in successive crops of winter wheat in relation to initial populations and fungicide treatments. Crop Protection 9 135–142. Bateman G. L.; Gutteridge R. J. (1996) Incidence of eyespot and selection of W-type and R-type of Pseudocercosporella herpotrichoides in sequences of different cereal species.Aspects of Applied Biology 47 437–440. Bateman G. L.; Jenkyn J.F. (2000) Towards better understanding and management of cereal stem-base diseases. Proceedings of the BCPC Conference – Pests & Diseases 2000 1 119–126. Bateman G. L.; Landau S.; Welham S. J. (1995) Sensitivity to prochloraz in populations of the eyespot fungus Pseudocercosporella herpotrichoides in relation to fungicide treatments and their efficacy in continuous winter wheat. Annals of Applied Biology 126 235–247. Bateman G. L.; Murray G.; Gutteridge R. J.; Coskun H. (1998) Effects of straw disposal and depth of cultivation on populations of Fusarium spp. in soil and on brown foot rot in continuous winter wheat. Annals of Applied Biology 132 35–47.Burnett F. J.; Oxley S. P. J.; Laing A. P. (2000) The use of PCR diagnostics in determining eyespot control strategies. Proceedings of the BCPC Conference – Pests & Diseases 2000 1 107–112. Goulds A.; Fitt B. D. L. (1991) The development of eyespot on stems of winter wheat and winter barley in crops inoculated with W-type or R-type isolates of Pseudocercosporella herpotrichoides. Zeitschrift für Pflanzenkrankheiten und Pflanzenschutz 98 490–502. King J. E.; Griffin M. J. (1985) Survey of benomyl resistance in Pseudocercosporella herpotrichoides on winter wheat and barley in England and Wales in 1983. Plant Pathology 34 272–283. Leroux P. (1998) Progress and problems in the control of cereal eyespot fungi in France. Pesticide Outlook 9 1998 34–38. Nicholson P.; Turner A. S. (2000) Cereal stembase disease – a complex issue. Proceedings of the BCPC Conference – Pests & Diseases 2000 1 99–106. Prew R. D.; Ashby J. E.; Bacon E. T. G.; Christian D. G.; Gutteridge R. J.; Jenkyn J. F.; Powell W.; Todd A. D (1995) Effects of incorporating or burning straw and of different cultivation systems on winter wheat grown on two soil types 1985-91. Journal of Agricultural Science Cambridge 124 173–194. West S. J. E.; Booth G. M.; Beck J. J.; Etienne L. (1998). A survey of Tapesia yallundae and Tapesia acuformis in UK winter wheat crops using a polymerase chain reaction diagnostic assay. Proceedings of the 1998 Brighton Crop Protection Conference – Pests & Diseases 3 1029–1034. Geoff Bateman and John Jenkyn have spent 29 and 33 years respectively as plant pathologists based at Rothamsted. Both have wide experience of research on cereal diseases including their epidemiology effects and control.

ISSN:0956-1250    

DOI:10.1039/b104740j

出版商:RSC    

年代:2001

数据来源: RSC