摘要:

SUMMARYPrevention of the use of DDT has been made the target of a powerful propaganda drive in certain prosperous countries because, it is stated, DDT is a danger to man and harms wild life. On the other hand, DDT is by far the most economical, effective and safe insecticide for many uses, particularly for protecting men from certain insect‐borne diseases and for enabling cotton to be grown in poor countries. Some risks can be reduced by eliminating those uses of DDT for which adequately safe, economical and effective substitutes exist, whether chemical or not; other risks can be reduced in other ways. The known risks to men are trivial, except when DDT concentrate is deliberately drunk, and the scare is made up of unknown risks ‐which could equally exist with any object or material, new or old. Risks to wild life have been greatly exaggerated and scares depending on falsehoods have become current. The postulated threat of progressive accumulation of DDT along a long food chain is not adequately supported by evidence, much of which has been misinterpreted.Thus the main dilemma is how to balance the great and undoubted benefits of DDT to millions of men, women and children against harm to wild life, sometimes genuine and remediable and sometimes dubious.People who campaign for banning have possibly failed to recognize this dilemma. On the other hand, they may have made a deliberate choice in favour of wild life. In that case, to be logical, they should also oppose all other means of preventing premature death of other people, which they might justify as a means of postponing over‐population. The use or abuse of DDT is a minor component in the rise of the worl's popul

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1972.tb01276.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SUMMARYFrom 1967 to 1971, wheat bulb fly females caught by sweeping from a number of localities contained mature eggs from the third week of July to the end of August.In 1971 when female wheat bulb flies were caught by sweeping, by white water traps, by suction traps as well as by light traps, the first flies containing mature eggs were caught 29 days after the first detected emergence while the first batch was laid 29–58 days after first emergence. The peak period of egg laying occurred in the fourth week of July, 24–38 days after the peak emergence. The second batch of eggs was laid when the flies were 8 weeks old, 29 days after the first; the peak for this batch was 35 days after the first. A few females laid a third batch of eggs 28 days after the first record of the laying of the second batch. A female that lives sufficiently long to lay the third batch of eggs is at least 12 weeks old. In 1970, when emergence started earlier in June, ripening and laying of eggs of the three batches was also earlier.After the harvest of cereal crops more females were caught by white water traps placed on the fallow than by other methods.The most important pathogen affecting adult wheat bulb flies was a fungus, probablyEntomophthora muscae.When infection occurred early in July, fewer eggs from the first batch were laid than when infection developed later. Fewer flies were infected in 1971 than in 1970.To be effective against wheat bulb fly in the early spring, control measures‐should be applied against adults before their eggs mature in early July of the preceding

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1972.tb01277.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SUMMARYWhen sugarbeet leaves were inoculated simultaneously with the parasiticPhoma betaeand the saprophyticAureobasidium pullulansorTorulopsis Candida, the development of expanding lesions caused byP. betaewas curtailed. Two other common saprophytes,Sporobolomyces pararoseusandCladosporium cladosporioides, also decreased numbers and sizes of expanding lesions in the presence of pollen. The numbers of saprophyte cells applied to inoculum areas were similar to those occurring naturally on sugarbeet leaves in the summer.Lesion development was not affected by a mixture of heat‐killed cells of the four saprophyte

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1972.tb01278.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SUMMARYThe fungal microflora of orchard (cock's‐foot) grass seed(Dactylis glomerataL.) was determined for 140 samples obtained from thirteen countries. The microflora was assessed by visual examination of dry seed (20–50 x), by microscopic examination of centrifuged seed washings and by incubating seed on 2 % malt extract agar (MA) under a 10‐day regime of diurnal cycling of temperature (23‐9oC/i8‐3oC) and near‐ultraviolet radiation (12 h NUV/ 12 h dark). More than twenty‐five species of potentially pathogenic fungi and forty species of saprophytes were detected. The pathogens included anAscochytasp.,Botrytis cinerea, nine species ofDrechsleraincludingD. dactylitis(infested 23% of seed lots) andD. Useptatum(10% of seed lots), five speciesoiFusariumincludingF. avenaceum(5 % of seed lots),Lep‐tosphaeriasp.,Phleosporasp.,Phomasp.,Phomopsissp.,Pyrenochaetasp.,Rhizoctoniasp.,Rhynchophomasp.,Septoriasp. andStagonosporasp. Many more fungi were identified from seed plated on MA and exposed to NUV than by examination of seed washings or visual examination of dry seed. Several of the fungi that were detected are known to pro

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1972.tb01279.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SUMMARYPure cultures of fifty‐two species of plant pathogenic and saprophytic fungi isolated from orchard (cock's‐foot) grass seed(Dactylis glomerataL.) were incubated either in total darkness or exposed to a diurnal cycle of near‐ultraviolet (NUV) radiation (12 h NUV/12 h darkness). Twenty‐four species sporulated only after exposure to NUV including seven species ofDrechslera, five species ofFusarium, as well as speciesolAscochyta, Photna, Septoria, Pyrenochaeta, RhynchophomaandStagonospora;six species sporulated moderately in darkness but more profusely following exposure to NUV; twenty species sporulated whether they were irradiated or not; and only two species failed to sporulate. To assess the pathogenic fungal microflora of orchard grass seed accurately, seeds should be incubated under a daily regime that includes NUV to induce spor

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1972.tb01280.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SUMMARYThe uptake of14C and movement of14C‐labelled assimilates in wheat plants inoculated withOphiobolus graminiswas examined following exposure of the second youngest leaf to14CO2. Autoradiographs of plants with infected seminal roots showed that assimilates were not translocated past the sites of root infection but accumulated in the undamaged portions of infected root systems, in particular the developing crown roots. There was no evidence that assimilates accumulated in the vicinity ofO. graminislesions.The net assimilation of14CO2by wheat plants over a 5 h feeding period was not significantly affected byO. graminisinfection. However, infection reduced the amount of14C lost through respiration. Infection delayed the transfer of labelled assimilates from the fed leaf to the remainder of the plant but increased the proportion translocated to the roots. The latter effect was not apparent when infected plants were continuously irrigated during, and for 20 h following, the feeding perio

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1972.tb01281.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SUMMARYOulema melanopaandO. lichenisboth transmit cocksfoot mottle and phleum mottle viruses with similar efficiencies. The viruses were serologically dissimilar and did not cross‐protect against each other in barley. Both viruses were acquired after a few minutes feeding, but longer acquisition feeding periods increased both the efficiency of transmission and persistence in the vectors. Acquisition of either virus increased vector mortality whilst acquisition of both together did not. When both viruses were ingested, only one was transmitted. Each virus could be recovered from haemolymph and faeces, but regurgitation was not observed and could only be induced with the greatest difficulty. The results suggest possible circulative transmission of some beetle‐borne viru

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1972.tb01282.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SUMMARYSevere stunting of parsley plants, with leaf chlorosis and reddening was reported from four localities in Britain in 1968‐70. Affected plants were collected from thirteen sites in Bedfordshire, Buckinghamshire, Cheshire and Bristol, and five viruses (designated PV1‐PV5) were isolated from them. The viruses were distinguished by electron microscopy, host range and type of aphid transmission.From diagnostic reactions in a range of host species and its transmission byCavariella aegopodiiScop., the most frequently isolated virus (PV4) and the principal cause of the parsley disease was identified as carrot mottle virus (CMotV).The other four viruses were infrequently isolated. PV1, PV2 and PV3 were transmitted in the non‐persistent manner byMyzus persicaeSulz. Each was purified and identified serologically as western celery mosaic virus, cucumber mosaic virus and broad bean wilt respectively. PV5 was not fully identified, but was transmitted byC. aegopodiiin the presence of CMotV and had particlesca.500 nm in length. Each of these viruses was re‐transmitted to parsley, but induced slight symptoms

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1972.tb01283.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SUMMARYA non‐persistent, aphid‐transmitted virus (PV3) found in parsley in Britain was cultured inChenopodium quinoa.It was mechanically transmissible, relatively stablein vitroand had polyhedral particles approximately 30 nm in diameter.Virus particles occurred within the cells as crystals, scrolls and tubular structures. In purified preparations, virus particles were mostly aggregated, especially in the presence of salts.PV3, nasturtium ringspot virus and broad bean wilt virus were found to be closely related serologica

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1972.tb01284.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SUMMARYIn 1966‐9 the spread of leaf roll and severe mosaic (Virus Y) was investigated in seed and ware areas in South Wales. The use of disulfoton granules at planting time greatly reduced the spread of leaf‐roll virus in both areas but had less effect on the spread of severe mosaic. Foliar sprays with formothion did not reduce the spread of either virus. Practical considerations are briefly discus

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1972.tb01285.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY