摘要:

AbstractThree pesticides, dimethoate, pirimicarb and fenpropimorph, had a negative impact on the colonization of a sterilized soil by a natural population of soil protozoa. Fenpropimorph has an effect at the lowest concentration applied; 25 mg litre−1. Dimethoate reduced the soil respiration significantly for about 10 days after application. In single species cultures of soil protozoa in liquid media, a flagellateCercomonassp., was a better test organism than a ciliate,Colpodasp., or an amoeba,Acanthamoebasp., with respect to interpretation of dose‐response curves and ease of observat

ISSN:0031-613X    

DOI:10.1002/ps.2780420202

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractA laboratory study was performed to investigate the relationship between chemical (non‐biological) and microbial degradation of cyanazine and atrazine in soils ranging in pH from 5.3 to 8.1. Atrazine degradation was dominated by chemical processes in both a moderately acidic and a neutral pH soil, but showed a significant microbial involvement in the neutral pH soil. The primary cyanazine degradative mechanism was dependent on soil properties. Cyanazine was short‐lived in neutral to slightly basic soils, due to rapid microbial degradation. Cyanazine amide and cyanazine acid were the major metabolites formed. In a moderately acidic soil, microbial degradation was slowed and chemical processes were the primary means of cyanazine degradat

ISSN:0031-613X    

DOI:10.1002/ps.2780420203

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe nonsteroidal ecdysteroid agonist tebufenozide (RH‐5992) was tested on larval stages of a number of lepidopteran species by topical application and by feeding on treated leaves. LC50, values in the range 0.03–0.10 mg litre−1were obtained for third to sixth instars ofSpodoptera exempta(Walker) when insects were fed on leaves dipped in aqueous emulsions of the compound, while first to fifth instars ofSpodoptera exigua(Hübner) were less susceptible (LC50values in the range 2.5–10.5 mg litre−1). When insects were topically treated, susceptibility of last‐instar larvae of Lepidoptera tested decreased in the orderSpodoptera exempta, Mamestra brassicaeL.,Spodoptera littoralis(Boisd.)S. exiguaandGalleria mellonellaL. Tebufenozide induced a premature and lethal larval moult in larval Lepidoptera within 24 h of treatment. Most larvae died in their old larval cuticle. Other aberrations included inhibition of weight gain and feeding, extrusion of the hindgut, loss of hemolymph and an abnormal and lethal pupation. In contrast, tebufenozide at similar doses/concentrations had no activity on larval instars ofLeptinotarsa decemlineata(Say) andDiabrotica virgifera virgifera(LeConte), nymphs ofPodisus sagitta(F.) and larvae ofLocusta migratoria migratorioides(R.&F.). It had a chemosterilizing activity inS. exigua, resulting in a total inhibition of oviposition within two days of continuous treatment at doses of ⩾ 10 mg litre−1.On the other hand, all deposited eggs were viable. Similar effects on reproduction occurred inL. decemlineata, but at highe

ISSN:0031-613X    

DOI:10.1002/ps.2780420204

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe promotion of hydrolysis of some organophosphorus pesticides by mercury(II) ion was studied. The presence of mercuric chloride at 20 mg litre−1increased the initial hydrolysis rates of malathion, fenitrothion, fenthion and parathion‐methyl in pH 5.5 buffer by two to three orders of magnitude. The hydrolysis was found to be first order with respect to both mercury(II) ion and the pesticide. The main hydrolysis product was 3‐methyl‐4‐nitrophenol for fenitrothion, and 4‐nitrophenol for parathion‐methyl. It is postulated that the reaction involves the formation of a 1:1 complex and a very slow regeneration of the mercury(II) ion from the reacted complex. Mercury(II) ion had little effect on the organophosphorus pestici

ISSN:0031-613X    

DOI:10.1002/ps.2780420205

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe effects of application rate, volume, solvent and soil moisture content on the kinetics of mineralization and degradation, of [14C] permethrin have been studied in a sandy loam soil under standard laboratory conditions. During the incubation period, up to 32 days, the temperature and moisture level of the soil were controlled. Apart from the effects of application rate, which have been widely reported, application volume had the most significant effect on mineralization rate andT1/2. [14C]Permethrin, at a level of a 1 mg kg−1in the soil, applied in 100 μl of methanol, resulted in the evolution of 14% of the applied radiochemical as [14C] carbon dioxide over 30 days. The same level applied in 1000 μl mineralized at a faster rate, with 30% [14C]carbon dioxide evolved over 30 days.The test chemical applied to soil in methanol mineralized at a significantly faster rate than a similar concentration applied in ethanol. There was no significant difference when comparing applications made using acetonitrile with those using methanol or ethanol. The addition of formulation ingredients resulted in little or no variation in mineralisation rate compared to an equivalent application volume of methanol/wa

ISSN:0031-613X    

DOI:10.1002/ps.2780420206

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractA spectrophotometric method has been developed for the determination of ziram (zinc bis(dimethyldithiocarbamate)) and zineb (zinc ethylenebisdithiocarbarnate) by converting these into a zinc‐4‐(2‐pyridylazo)resorcinol complex, which is dissolved in acetone and water and the absorbance measured at 490 nm against a reagent blank. Beer's law is obeyed over the concentration ranges 0.025‐1.25 and 0.025‐1.5 mg litre−1for ziram and zineb respectively in the final solution. The method is sensitive and can be used for the direct determination of ziram and zineb in commercial formulations, grains (rice and wheat) and synthetic mixtures (in the presence of various other dithiocarbamates). The limit of determination of ziram and zineb from foodstuffs in

ISSN:0031-613X    

DOI:10.1002/ps.2780420207

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractAt the beginning of the 1990s, insecticides with novel modes of action, such as buprofezin, pyriproxyfen and diafenthiuron, were introduced for controlling the whiteflyBemisia tabaci(Gennadius) in cotton and other crops. In order to delay the onset of resistance to these novel insecticides, as well as to the efficient conventional ones, an insecticide resistance management (IRM) strategy was implemented in 1987 in cotton fields in Israel. The main purposes have been to combat resistance to available, efficient insecticides and to prolong the life‐span of new insecticides by optimizing their use and preserving natural enemies during the peak of their activity. A rotation programme was applied, using insecticides of different modes of action, rotated according to the generation duration of the relevant pests. The strategy included explanatory and educational campaigns, and was accompanied by an extensive resistance monitoring programme conducted throughout the year in greenhouses and during the summer in cotton fields. Bioassays of whiteflies collected from cotton fields indicated that one treatment with pyriproxyfen in cotton fields during a one‐month period, followed by an additional treatment with buprofezin (if required), did not markedly alter the susceptibility ofB. tabacito either compound. In addition, no appreciable increase of resistance to the available conventional insecticides was observed, although some changes in susceptibility were noticed during the cotton season. In some greenhouses without an IRM programme, ac.tenfold increase in resistance to buprofezin was found after two or three applications of this compound in each season. Ac.500‐fold increase of resistance to pyriproxyfen was recorded after three successive applications of this compound in a greenhouse. These findings demonstrate the necessity for an IRM strategy to be implemented in both open fields and greenh

ISSN:0031-613X    

DOI:10.1002/ps.2780420208

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe cosmopolitan whitefly species,Bemisia tabaci(Gennadius) andTrialeurodes taporariorum(Westwood) have always been regarded as pests to a large range of worldwide crops. Both species are capable of transmitting plant viruses, withT. vaporariorumbeing the vector of only a few ‘clostero’‐like viruses andB. tabacithe vector of viruses in several groups. The largest group of viruses transmitted byB. tabaciare the geminiviruses andB. tabaciis known to transmit around 60 members.Until recently,B. tabacihad been associated with only a limited range of host plants within any one region, although its total potential host range was large. Virus transmission was confined within the plant host range of each regional population ofB. tabaci.The emergence of the polyphagous ‘B’ biotype ofB. tabaciwith its increased host range of more than 600 plant species, has resulted in geminiviruses infecting previously unaffected crops. As the ‘B’ biotype spreads further into Europe, European field and glasshouse crops have been shown to be susceptible to whitefly‐transmitted viruses already endemic to other parts of the world.More than 20 colonies ofB. tabaci, including both ‘B’ and non‐‘B’ biotypes from disparate global locations have been compared for their ability to transmit more than 20 geminiviruses. All but two highly host‐specific colonies were capable of transmitting most geminiviruses tested. However, some viruses were transmitted more efficiently than others. The virus coat protein or capsid is essential for vector recognition and transmission. By comparing transmissible viruses at the molecular level to viruses that are no longer whitefly‐transmissible, the active epitope on the virus coat protein could be identified for designing fu

ISSN:0031-613X    

DOI:10.1002/ps.2780420209

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractIn autumn 1987, the first observations were made in the Netherlands of a whitefly species identified as type ‘B’ of the sweet potato whitefly,Bemisia tabaci(Gennadius), on the host plant poinsettia,Euphorbia pulcherrimaWilld. ex Klotzsch. Although an eradication programme was initiated, total eradication was not obtained. Over the yearsB. tabacihas persisted on poinsettia and slowly spread to other crops like Begonia, Bouvardia, Gerbera and Hibiscus. Vegetables like tomato, cucumber and egg plant have also become infested.B. tabacioften develops extensively during the summer season due to its better adaptation to temperatures of ⩾25°C compared with the greenhouse whitefly, which develops more readily at 20°C. During the poinsettia growing season, high population numbers ofB. tabaciwill not develop, but any plants showing visible signs of infestation, such as an empty pupal case, are rejected at the auction. The integration of biological and chemical control is expected to show better potential than the use of insecticides, as insecticide resistance has already been observed. Several natural enemies, such as certain strains of the parasitoidsEncarsia formosaGahan andEretmocerus californicusHoward, as well as the predatorsDelphastus pusillusLeconte andMacrolophus caliginosusWagner, are being tested in green‐houses. Research is also carried out regarding the use of insectpathogenic fungi such asAschersoniaspp.,Verticillium lecanii(Zimm.) Viegas andPaecilo

ISSN:0031-613X    

DOI:10.1002/ps.2780420210

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe following are extended summaries based on papers presented at a meeting of the Physicochemical and Biophysical Panel of the SCI Pesticides Group, held on 25 January 1994 at the SCI, 14/15 Belgrave Square, London SWIX 8PS, UK. The summaries published here are entirely the responsibility of the authors and do not reflect the views of the Editorial Board of Pesticide Science.

ISSN:0031-613X    

DOI:10.1002/ps.2780420211

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY