bluuebunny/crossref_metadata_2025 huggingface dataset:
The metabolism of tralkoxydim in field‐grown spring wheat and maize plant cell suspension culture
Authors: Hadfield Stephen T. , Wilson Anahita , Kuet Sui F. , Mason Robert
Published: November 2006

Abstract: The metabolism of tralkoxydim was studied in wheat grown under field conditions and treated at a rate equivalent to 345 g a.i. ha −1. Maize plant cell suspension culture was used as a means of indicating the nature of the primary metabolic process, and also as a source of material for structural elucidation. The principal metabolic process in wheat involved hydroxylation of the p‐methyl function of the aromatic ring. This occurred in conjunction with a range of possible transformations of the (ethoxyimino)propyl function, or oxidative cleavage of the cyclohexanedione ring. All the initial metabolic products were amenable to further conjugation with a range of endogenous sugars.
Photolysis of pirimicarb in water under natural and simulated sunlight conditions
Authors: Romero Esperanza , Schmitt Phillipe , Mansour Mohamed
Published: November 2006

The photostability of pirimicarb, (2‐dimethylamino‐5,6‐dimethylpyrimidin‐4‐yl dimethylcarbamate) in aqueous media, under natural and artificial sunlight irradiation conditions, is reported. The pH of the irradiated solutions remained constant during degradation time. The photodegradation mechanism seemed to be similar under both conditions, but the half‐life was found to be about three times longer under natural than under artificial conditions. Four main photo‐products (1, 2, 3 and 4) were isolated and identified by spectroscopic methods. It is proposed that a common photodegradation pathway exists for pirimicarb under both irradiation conditions. The results obtained from the photodegradation of pirimicarb and of its four main products isolated on solid phase permit the construction of a possible photodegradation pathway. Photoproduct 4 (2‐methyl‐formylamino‐5,6‐dimethyl‐4‐hydroxypyrimidine) is here described for the first time.
Influence of carbon and nitrogen application on the mineralization of atrazine and its metabolites in soil
Authors: Assaf Nasser A. , Turco Ronald F.
Published: November 2006

It has been proposed that levels of carbon and nitrogen in soil affect the rate at which triazine herbicides degrade. The present study was designed to investigate the effects of varying the levels of initial soil carbon and nitrogen as well as the effects of a later carbon addition on the mineralization of atrazine and its metabolites in soil. Atrazine degradation in soils amended with carbon as mannitol, and with nitrogen as urea, at levels of 10, 30, 50, or 80 mg kg−1 mannitol, urea, or mannitol and urea was similar to degradation in unamended soils. Only 39% of applied atrazine was mineralized after 326 days regardless of the initial carbon or nitrogen treatment. In contrast, a second mannitol amendment of 1 g kg−1 soil at day 140 increased [14C]carbon dioxide evolution by an additional 17% as a result of enhancing the mineralization rate of the atrazine metabolites. This conclusion is supported by our finding that periodic extraction of the soil with methanol followed by quantification on HPLC showed complete dissipation of the parent atrazine in 120 days. The metabolites hydroxyatrazine (HA), deisopropylatrazine (DIA), deethylatrazine (DEA), and diaminochlorotriazine (DACT) began to appear in the methanol extract 10 days following atrazine application. The greatest concentrations of HA, DEA, DIA. and DACT in the methanol extracts were 19, 12.4, 10.1, and 6.7% of applied atrazine, respectively. These concentrations were observed at day 95 except for DEA where the concentration continued to increase until day 142. A second soil extraction with hydrochloric acid (1m) + methanol (20 + 80 by volume) recovered additional HA, deethylhydroxyatrazine (DEHA), deisopropylhydroxyatrazine (DIHA), and DACT. When the extraction data were combined, 31.9, 12.4, 10.1. 10.2, 12.0 and 7.8% of applied atrazine was recovered as HA, DEA, DIA, DEHA. DIHA, and DACT, respectively. Combustion of the extracted soil showed 20% of the applied atrazine remained as soil‐bound residues after 326 days.
Cuticular sorption and desorption of a nonionic diethylene glycol monooleate surfactant
Authors: Tan Siyuan , Crabtree Garvin D.
Published: November 2006

Sorption and desorption of ‘Pegosperse’ 100‐O(PEG 100‐O; diethylene glycol monooleate, containing 15% diester) surfactant by unaltered (CM) and dewaxed (DCM) adaxial cuticle membranes isolated from apple (Malus pumila M.) leaves were studied. The aim of this study was to understand interactions between surfactants and cuticles. Enzymatically isolated cuticles were soaked in buffer or PEG 100‐O solution (pH 7–0). and the weight changes of cuticles were measured to determine the amount of surfactant sorbed or desorbed by the cuticles. For very low surfactant concentrations, sorption was measured by changes in the surface tension of the solutions. PEG 100‐O sorption by both the CMs and the DCMs occurred mainly in the first three hours and was concentration‐dependent. The DCMs always sorbed more surfactant than the CMs. Desorption of PEG 100‐O from both CMs and DCMs was rapid in the first few hours and then decreased to a relatively low rate until the surfactant was totally desorbed from the cuticles after about two months. The sorption and complete desorption of the surfactant by both CMs and DCMs show that PEG 100‐O interacts with both cutins and waxes of the cuticles and the interactions are reversible.
Solid‐phase thermal decomposition of benomyl
Authors: Bartolomei Monica , Cignitti Maurizio , Cotta‐Ramusino Marina , Iela Maria T. , Soccorsi Laura
Published: November 2006

Solid‐phase decomposition of benomyl has been investigated by thermo‐gravimetric analysis; the degradation process (heating rate of 1°C min−1 under nitrogen flux) starts at c. 65°C. Semi‐empirical quantum mechanical methods have been used to characterize the benomyl molecule and to obtain information on a possible degradation mechanism.
Mechanisms of dicarboximide ring opening in aqueous media: Procymidone, vinclozolin and chlozolinate
Authors: Villedieu Jean C. , Calmon Michelle , Calmon Jean P.
Published: November 2006

The hydrolysis kinetics of the dicarboximide fungicides procymidone, vinclozolin and chlozolinate in neutral and alkaline solutions of pH 60 to 13·7 at 25°C have been determined conjointly by ultraviolet spectrophotometry and by high performance liquid chromatography. Under alkaline conditions, the fungicides undergo attack by the hydroxide ion on a specific carbonyl group and the rate of hydrolysis increases proportionally to the hydroxide ion concentration. Procymidone gives quantitatively and irreversibly 2‐(3,5‐dichlorophenylcarba‐moyl)‐l,2‐dimethylcyclopropanecarboxylate. The reaction is not subject to general base catalysis and experimental data are in agreement with a rate‐determining attack by the hydroxide ion. After a rapid hydrolytic loss of the ethoxycarbonyl substituent from chlozolinate, the dicarboximide ring cleavage of the two other fungicides leads, by mechanisms which differ with respect to the type of base catalysis and the rate‐determining step, to the corresponding anilides, producing as intermediates the carbamic acids, which undergo loss of carbon dioxide. The hydrolysis of vinclozolin and chlozolinate yields, respectively, N‐(3,5‐dichloro‐phenyt)‐2‐hydroxy‐2‐methylbut‐3‐enanilide and N‐(3,5‐dichlorophenyl)‐2‐hydroxy‐propanilide.
Metabolism of amitrole in apple: III. Model systems
Authors: Schneider Bernd , Stock Manfred , Bohm Hartmut , Schneider Gernot , Schütte Horst‐Robert , Schreiber Klaus , Brauner Angela , Köster Johannes , Kaußmann Ernst U.
Published: November 2006

Excised shoots from apple trees and cell suspension cultures were used as model systems to study the metabolism of [3,5‐14C]amitrole in Malus domestica Borkh. Significant differences in the metabolism of the compound applied were observed with excised shoots, cultured cells and whole apple trees. The major metabolite in excised shoots was aminotriazolylalanine which occurred both in the free form and as conjugates. The major metabolite from whole plants. triazolylalanine, was detected in shoots in minor amounts only. In cell suspension cultures, the type of metabolism strongly depended on the concentration of amitrole when initially applied. At 10 −3 m or lower, mainly aminotriazolylalanine was formed. Depending on the concentration of the active ingredient, this metabolite predominantly occurred in free form or as glycosides. At concentrations above 5 × 10−4 M a new metabolite, 3,5‐dihydroxytriazole, was detected which was the only metabolite found at 5 × 10−3M. Significant amounts of nonmetabolized amitrole remained in the medium.
2‐Trichloromethylbenzimidazole, a new selective chromogenic reagent for detection of some heteroaromatic pesticides on thin‐layer chromatographic plates
Authors: Konopski Leszek
Published: November 2006

A highly selective method for the detection of several pesticides containing a heteroaromatic ring in the molecule (e.g. nicotine, pyrifenox or prochloraz) on thin‐layer chromatographic (TLC) plates is described. The necessary detection condition is the presence in the ring of at least one tertiary nitrogen atom without substitutents on the two adjacent carbon atoms and, in the case of azoles, the protection of a secondary NH group by an alkyl or acyl group. The detection is realized by spraying the developed chromatogram with an acetone solution of 2‐trichloromethylbenzimidazole and subsequently heating at 100‐150°C in a drier. The detection limit is 20 ng to 10 μg depending on the detected compound. Some pesticide formulations may be analyzed using this method.
Differential effects of the acylurea insect growth regulator teflubenzuron on the adults of two endolarval parasitoids of Plutella xylostella, Cotesia plutellae and Diadegma semiclausum
Authors: Furlong Michael J. , Verkerk Robert H. J. , Wright Denis J.
Published: November 2006

The acylurea chitin synthesis inhibitor, teflubenzuron (‘Nomolt’® SC) showed no apparent activity against adult males of Diadegma semiclausum Hellén or Cotesia plutellae Kurdj. when applied to foliage at a rate ( = 50 g a.i. ha−1) approximating to 2 × field usage. In contrast, the pyrethroid cypermethrin (‘Cymbush’® EC) showed appreciable foliar activity (at rates = 10–50 ga.i. ha−1) to D. semiclausum but showed low activity against C. plutellae. When single adult female D. semiclausum were pre‐treated with teflubenzuron (= 50 g a.i. ha−1) and then exposed to 5. 10. 25, 50 or 100 second‐instar host larvae, the number of purasitoid cocoons formed was significantly reduced compared with controls except at the lowest host density (P 0‐05). However, there was no evidence that teflubenzuron had a host density‐dependent effect on parasitism by D. semiclausum. Teflubenzuron had no significant effect on host parasitism in an equivalent experiment with C. plutellae (P > 0‐05) except at the median host density. When batches of ten host larvae were introduced at hourly intervals to female D. semiclausum pre‐treated with teflubenzuron (= 50 g a.i. ha−1), the number of cocoons formed in the first two batches was not significantly different from untreated controls (P > 0‐05), whereas teflubenzuron significantly reduced the number of cocoons in the next three batches of host larvae (P < 0‐05). This suggests that teflubenzuron may affect chitin synthesis in developing eggs within female D. semiclausum but has little or no effect on pre‐formed eggs which are more likely to be oviposited first. Teflubenzuron had no significant (P > 0‐05) effect on parasitism by C. plutellae when presented with batches of host larvae. When female D. semiclausum and C. plutellae were placed in the same host arena, the former showed a 3‐fold greater rate of parasitism. Pre‐treatment with teflubenzuron significantly reduced parasitism by D. semiclausum (P > 0‐05) but had no significant effect with C. plutellae (P > 0‐05) although the latter species failed to exploit the reduction in parasitism by D. semiclausum. The differential response of D. semiclausum and C. plutellae to insecticides is discussed in relation to the relative rates of establishment of these species in Malaysia.
Chemical versus microbial degradation of cyanazine and atrazine in soils
Authors: Blumhorst Michael R. , Weber Jerome B.
Published: November 2006

A 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 degradation.
Extended summary joint BCPC/SCI symposium seed treatment: Progress and prospects.
Authors: Brent Keith J.
Published: November 2006

The following extended summary represents an overview of the topics and points of interest raised at the above meeting organised by T. J. Martin, British Crop Protection Council, and held at the University of Kent, Canterbury, UK on 5–7 January 1994. The summary is a personal and highly selective appraisal of the meeting and any views expressed do not necessarily reflect those of the Editorial Board of Pesticide Science.
N‐(pyrid‐3‐yl)thioureas and derivatives as acaricides. I. Synthesis and biological properties
Authors: Pascual Alfons , Rindlisbacher Alfred
Published: November 2006

In the course of optimization studies around diafenthiuron, the central aromatic nucleus linked directly to the thiourea unit was replaced by a pyridine moiety. A series of N‐(pyrid‐3‐yl)thioureas, ‐isothioureas and ‐carbodiimides was synthesised and evaluated for acaricidal activity. The synthetic methodology used and the screening results against some spider mites (Tetranychus spp. and Panonychus ssp.) are discussed.
Esterase isozymes in Lygus hesperus: Characterization and relationship with organophosphate resistance
Authors: Xu Gang , Brindley William A.
Published: November 2006

Esterases of Lygus hesperus Knight from five field and one laboratory populations were separated by non‐denaturing polyacrylamide gel electrophoresis and were characterized for inhibition and substrate specificity. There were six zones of esterase activity toward naphthyl ester substrates. Significant inter‐ and intra‐populational polymorphisms were observed. All the isozymes were carbo‐xylesterases that were sensitive to inhibition by paraoxon and insensitive to eserine or EDTA (ethylenedinitrilotetraacetic acid). Carboxylesterases from L. hesperus more readily hydrolysed naphthyl esters with short side chains. Molecular weight estimation by non‐denaturing polyacrylamide gel electrophoresis revealed that Est‐1, the specific band of older females and eggs, contained two enzymes with relative molecular masses of 140000 and 112000. The four esterase allozymes in Est‐3 had an average relative molecular mass of approximately 106000. The frequency of one putative allozyme in Est‐3 was directly correlated with the LC50 values of trichlorfon (to which L. hesperus has become resistant). The developmental and distribution variability of the esterase isozymes are compared.
Association between elevated activity of aryl acylamidase and propanil resistance in Jungle‐rice, Echinochloa colona
Authors: Leah Jon M. , Caseley John C. , Riches Charles R. , Valverde Bernal
Published: November 2006

Aryl acylamidase (aryl‐acylamine amidohydrolase, EC 3.5.1.13) activity has been measured in crude extracts from leaves of propanil‐susceptible (S) and propanil‐resistant (R) biotypes of the grass weed. Echinochloa colona (L.) Link from Columbia. Both specific and total amidase activity increased with plant age up to 15 days (four‐leaf stage), then decreased beyond 20 days to about 50% of the maximum at 36 days in both R and S E. colona biotypes. Specific activity with propanil in the R biotype was about 80% of that obtained for rice (Oryza sativa L.), compared to 25% in the susceptible biotype. The specific activity of the propanil amidase was three‐fold higher in the R biotype than in the S. Partially purified amidase extracts from rice and both S and R biotypes of E. colona were compared biochemically. Both rice and E. colona amidases had a pH optimum of 7.5 and native relative molecular masses, estimated by gel filtration, of 179 000 and 181 000, respectively. Out of six substrates tested, three produced appreciable activity (propanil, 4‐chloroacetanilide and acetanilide) in both rice and E. colona. Michaelis constants showed that the rice amidase had a higher affinity for propanil (0.36 mM) than had the E. colona enzyme (1.1 mM). Carbamates and organo‐phosphorus pesticides were shown to inhibit amidase activity in partially purified rice and E. colona extracts. Additional preliminary data have implicated peroxidase in the next step of propanil metabolism in vitro. These data demonstrate that increased aryl acylamidase activity contributes to resistance to the herbicide propanil in E. colona weeds. Also, a biochemical comparison of purified aryl acylamidases from S and R biotypes of E. colona is presented for the first time.
A review of biochemical mechanisms of warfarin resistance in the house mouse
Authors: Macnicoll Alan D.
Published: November 2006

The biochemical mechanisms of warfarin resistance in the house mouse (Mus musculus L.) have not been fully investigated. In some populations of warfarin‐resistant mice there is a reduction in sensitivity of hepatic vitamin K‐epoxide reductase to inhibition by warfarin. This is similar to a proposed mechanism of anticoagulant resistance in the Norway rat (Rattus norvegicus Berk.). The same enzyme in other warfarin‐resistant populations is, however, sensitive to warfarin inhibition. Other studies have indicated that detoxification may play a role in conferring warfarin resistance in house mice.
Warfarin‐based rodenticides: Mode of action and mechanism of resistance
Authors: Thijssen Henk H. W.
Published: November 2006

Warfarin and related substances have been in use as rodenticides for fifty years. They act by binding to the enzyme vitamin K 2,3‐epoxide reductase, thereby interrupting the cellular recycling of vitamin K. Vitamin K in its hydroquinone form is an essential cofactor for the synthesis of functional prothrombin and related blood‐clotting factors. The binding with the reductase is essentially irreversible, indicating these compounds have a prolonged half‐life in target tissues; 7–10 days for warfarin and congeners and over 100 days for the second generation rodenticides or ‘superwarfarins’ such as difenacoum, brodi‐facoum, and flocoumafen. Rat liver contains 1–2 nmole of enzyme per gram tissue which is a 4–5 fold overcapacity for maintaining effective vitamin K recycling. The use of warfarin as a rat poison has resulted in the natural selection of warfarin‐resistant rats. The resistance is inheritable. Two distinct warfarin resistance genotypes, Welsh and Scottish, have been identified, clearly differing in their biochemistry of vitamin K epoxide reductase. In the Welsh strain, resistance arises from an altered enzyme expressing reduced reactivity to warfarin, whereas the reductase from the Scottish strain is as sensitive as the normal enzyme, but the interaction with warfarin is now readily reversible. The altered enzyme leaves the Welsh rat in need of higher dietary vitamin K intake. The superwarfarins cope with the resistance by having their structures firmly bind with the altered enzymes. Reduced sensitivity to warfarin‐based rodenticides may also be pharmacokin‐etically based, arising from increased warfarin biotransformation. This mechanism may be responsible for resistance to some of the superwarfarins such as difenacoum. A third resistance mechanism may arise from an enhanced capacity to synthesize vitamin K from menadione, a commonly used additive in animal foods on farms. The choice of rodenticide in the case of warfarin resistance should be guided by the underlying mechanism of resistance.
1,3‐dichloropropene distribution in soil when applied by drip irrigation or injection in pineapple culture
Authors: Schneider Randi C. , Green Richard E. , Wolt Jeffrey D. , Loh Rhonda K. H. , Schmitt Donald P. , Sipes Brent S.
Published: November 2006

The fumigant nematicide, 1,3‐dichloropropene (1,3‐D VL; ‘Telone’ II) and a soluble liquid formulation, 1,3‐D SL were tested in a pineapple field experiment to evaluate the vapor movement of the two formulations in soil gas as well as the movement and persistence of 1,3‐D SL in soil profiles. Prior to planting, 1,3‐D VL (407 kg ha−1) was hand‐injected into the soil in two parallel rows per planting bed to approximate the practice of chisel injection. 1,3‐D SL (407 kg ha−1) was applied with 6 mm of water by drip irrigation through a drip tube in the center of the bed. Post‐plant applications of 1,3‐D SL (113 kg ha−1) were made at three‐month intervals during a two‐crop cycle. 1,3‐D concentrations in soil gas were lower at the plant line in the drip treatment compared with the 1,3‐D VL treatment, owing to differences in application method and fumigant placement. 1,3‐D in the vapor phase reached peak concentrations 24 h after injection in the 1,3‐D VL treatment compared with a peak at 48 h in the drip treatment. Post‐plant applications of 1,3‐D SL resulted in a three‐fold difference in peak 1,3‐D soil gas concentrations between replicate applications, the concentration being inversely related to soil moisture at the time of sampling. Drip application of 1,3‐D SL resulted in a relatively uniform distribution of 1,3‐D across the bed and to a depth of 45 cm. There was no effect of formulation on downward movement of 1,3‐D and persistence in soil profiles sampled two weeks and one month after application. Rainfall which occurred 9 days after pre‐plant 1,3‐D fumigation resulted in leaching of 1,3‐D to a depth of 150 cm in soil profiles. Due to the short half‐life of 1,3‐D, significant penetration of 1,3‐D in the soil was observed only when irrigation or rainfall occurred soon after application.
Movement of pesticides to surface waters from a heavy clay soil
Authors: Brown Colin D. , Hodgkinson Robin A. , Rose Derek A. , Syers J. Keith , Wilcockson Steve J.
Published: November 2006

A field experiment at Cockle Park, Northumberland on a clay loam soil (Dunkeswick series) cropped with winter wheat investigated the effects of drainage and season of application on pesticide movement. Isoproturon, mecoprop, fonofos and trifluralin were applied in two consecutive seasons at normal agricultural rates to three hydrologically isolated plots each of 0.25 ha. Two of the plots were mole‐drained and the third was an undrained control. Surfacelayer flow and drainflow from each plot were monitored at 10‐min intervals. Samples of flow were analysed for pesticides to evaluate transport of applied chemicals from the site. Despite widely differing properties (Koc 20–8000 ml g−1, t1/2 10–60 days), all four pesticides were found in surface‐layer flow and mole drainflow from the site. Maximum concentrations of pesticides in flow ranged from 0.1 to 121 μg litre−1 (aqueous phase) and < 0.2 to 48 μg litre−1 (particulate phase). Over two contrasting seasons, total losses of pesticides in flow followed total amounts of flow and were approximately four and five times larger, respectively, in 1990/91 than in 1989/90. The maximum loss occurred from the undrained plot and was 2.8 g isoproturon (0.45% of that applied). Total losses of autumn‐applied pesticides from an undrained plot were up to four times greater than losses from a mole‐drained plot. Mole drainage decreased movement of pesticides from this slowly permeable soil by reducing the amount of surfacelayer flow. Maximum concentrations of mecoprop and isoproturon in drainflow were 10–20 times larger following spring application than after application in autumn. Bypass flow down soil cracks was an important process by which pesticide was lost from the site, with transport to the drainage system via mole channels (55 cm depth) after less than 0.5 and 6.7 mm net drainage in the two winters.
Further studies in increased sensitivity to N‐phenylanilines in benzimidazole‐resistant strains of Botrytis cinerea and Venturia nashicola
Authors: Ishii Hideo , Josepovits Gyula , Gasztonyi Maya , Miura Tamiko
Published: November 2006

The ring‐substituted N‐phenylanilines, N‐(3‐chlorophenyl)aniline (MC‐1) and N‐(3,5‐dichlorophenyl)aniline (MC‐2) were tested for their antifungal activity against Botrytis cinerea Pers. ex Fr. and Venturia nashicola Tanaka et Yamamoto. In both fungi, increased sensitivity to MC‐1 and MC‐2 was clearly observed in ‘highly carbendazim‐resistant, diethofencarb‐sensitive’ (HR, S) phenotypes. Sensitivity was low in ‘carbendazim‐sensitive, diethofencarb‐resistant’ (S, R) and ‘intermediately carbendazim‐resistant, diethofencarb‐resistant’ (IR, R) strains. On cucumber cotyledons, other strains of B. cinerea, possessing the phenotype ‘highly carbendazim‐resistant, diethofencarb‐resistant’ (HR, R) were not controlled by either MC‐1 or MC‐2. Response to MC‐2 was also examined using random ascospore progenies from V. nashicola crosses. In these progenies, high‐level carbendazim resistance and MC‐2 sensitivity always segregated together. Sensitivity to MC‐2 is controlled by a single gene which is either identical to or very closely linked to one conferring high‐level resistance to carbendazim.
Pyriproxyfen, a novel insect growth regulator for controlling whiteflies: Mechanisms and resistance management
Authors: Ishaaya Isaac , Horowitz A. Rami
Published: November 2006

Pyriproxyfen, a novel juvenile hormone mimic, is a potent suppressor of embryogenesis and adult formation of the sweetpotato whitefly, Bemisia tabaci (Gennadius), and the greenhouse whitefly, Trialeurodes vaporariorum (Westwood). Dipping of cotton or tomato seedlings infested with 0 to 1‐day‐old eggs in 0.1 mg litre−1 resulted in over 90% suppression of egg hatch of both B. tabaci and T. vaporariorum. Older eggs were affected to a lesser extent. Exposure of whitefly females to cotton or tomato seedlings treated with pyriproxyfen resulted in oviposition of non‐viable eggs. The LC90 values for egg viability of B. tabaci and T. vaporariorum exposed to treated plants were 0.05 and 0.2 mg litre−1, respectively. Treatment of whitefly larvae with 0.04–5 mg litre−1 resulted in normal development until the pupal stage; however, adult emergence was totally suppressed. Second instars of B. tabaci exposed to 5 mg litre−1 pyriproxyfen, excreted honeydew at a level similar to the control level until the fourth instar (pupation), after which a strong reduction was observed. Inhibition of egg‐hatch on the lower surface of cotton leaves was observed when their upper surface was treated with 1–25 mg litre−1, indicating a pronounced translaminar effect. These findings indicate that pyriproxyfen is an efficient control agent of both B. tabaci and T. vaporariorum. The compound has been used successfully for controlling whiteflies in Israeli cotton fields since 1991.

Adults of B. tabaci collected from a rose greenhouse and from adjacent cotton fields were monitored during 1991–1993 for their susceptibility to pyriproxyfen. A high level of resistance was recorded in whiteflies collected from a greenhouse after three successive applications of pyriproxyfen. Based on LC50 values, the resistance ratio for egg‐hatch suppression was 554‐fold and, for adult emergence failure, 10‐fold. However, a single treatment of pyriproxyfen in cotton fields during the summer season (according to an insecticide resistance management (IRM) strategy) did not alter appreciably the susceptibility of B. tabaci to this compound. In order to prevent development of resistance, an attempt should be made to restrict its use to one treatment per crop season applied during the peak activity of the pest.

Pyriproxyfen can be alternated with other novel compounds such as buprofezin and diafenthiuron for controlling whiteflies in cotton, vegetables and ornamentals as part of integrated pest management (IPM) and IRM strategies. In pyriproxyfen‐ or buprofezin‐resistant strains of B. tabaci or T. vaporariorum, no appreciable cross‐resistance was observed among pyriproxyfen, buprofezin and diafenthiuron.
Urine excretion of pentachlorophenol (PCP) in occupational exposure
Authors: Barbieri Franco , Colosio Claudio , Schlitt Helmut , Maroni Marco
Published: November 2006

The pharmacokinetics of pentachlorophenol (PCP) excretion in urine was examined in four workers exposed to the biocide in the tannery and wood industries. PCP concentration in urine was significantly higher in morning samples than in afternoon or evening samples. This excretion pattern was observed during an exposure of several shifts and following a four‐week holiday period. The estimated half‐life for PCP urine excretion was 10 days. Biological monitoring of occupational exposure to PCP should be carried out by measuring the concentration of the compound in urine collected in the morning or before the workshift.
Synthesis and fungicidal activity of 1,4‐dithiino[2,3‐b]quinoxaline‐2,3‐dicarbonitriles
Authors: Romer Duane R. , Aldrich Brian L. , Pews R. Garth , Walter Richard W.
Published: November 2006

A series of eleven 1,4‐dithiino[2,3‐b]quinoxaline‐2,3‐dicarbonitriles was prepared by reaction of 2,3‐dichloroquinoxalines with disodium (2)‐2,3‐dimercapto‐2‐butenedinitrile in N,N‐dimethylformamide. These products were tested for in‐vitro fungicidal activity by a Minimum Inhibitory Concentration (MIC) method. Several of these compounds showed broad‐spectrum fungicidal activity. The activity exhibited by these compounds was greatly dependent upon the substituents of the quinoxaline ring, with the nitro‐substituted derivatives showing the highest levels of antifungal activity. None of the compounds prepared, however, showed fungicidal activity comparable to that of the commercial fungicides screened.
Phytotoxicity of trifluoromethyl‐ and methyl‐substituted dinitroaniline herbicides on resistant and susceptible populations of black‐grass (Alopecurus myosuroides)
Authors: James Elizabeth H. , Kemp Malcolm S. , Moss Stephen R.
Published: November 2006

A Petri‐dish assay was used to determine the phytotoxicities of the dinitroaniline herbicides pendimethalin, trifluralin, benfluralin and ethalfluralin, and the methyl‐substituted analogues of the last three herbicides, on susceptible (Rothamsted) and multiple‐herbicide resistant (Peldon) populations of blackgrass Alopecurus myosuroides Huds. The Peldon population showed a high degree of resistance to pendimethalin, which possesses a 3,4‐dimethyl substitution. The two populations were equally sensitive to trifluralin, benfluralin and ethalfluralin which do not possess ring‐methyl groups but contain a 4‐trifluoromethyl group. Substitution of the 4‐trifluoromethyl with a methyl group, as demonstrated by the analogues, reduced phytotoxicity, but to a much greater degree in Peldon than in the Rothamsted population. The study indicates that resistance to pendimethalin in the Peldon population is attributable to an oxidative degradation of the 4‐methyl group, analogous to that which occurs with resistance to chlorotoluron. The lack of cross‐resistance to the other dinitroaniline herbicides appears to be due to the absence of ring‐methyl or other groups which are vulnerable to oxidative degradation, trifluoromethyl groups being particularly resistant to this form of reaction.
Fenbutatin oxide, fate in soil after extensive commercial use in Italy and Spain
Authors: Gray Alan , Dutton Alan J. , Eadsforth Charles V.
Published: November 2006

The long‐term fate of the acaricide, fenbutatin oxide, in soil has been investigated. Residues of the compound and its two principal metabolites have been determined in soil samples obtained from citrus orchards in Italy and Spain where the product had been applied commercially over a period of 6–10 years.

The average fenbutatin oxide content in the upper 0–15 cm soil layer ranged from ⩽ 1 mg kg−1 to 5 mg kg−1 in sites receiving single and double applications per year. The residues were located primarily (> 95%) in the top 0–30 cm layer and there was virtually no movement of the compound through the soil to lower depths. Below 0.5 m depths, the sites contained average concentrations of ⩽ 0.01 mg kg−1, the limit of determination. No significant build‐up of residues was observed and the data indicate an approximate half‐life in soil of just less than one year.

Residues of the two metabolites, dihydroxy‐bis(2‐methyl‐2‐phenylpropyl)stan‐nane and 2‐methyl‐2‐phenylpropyl stannonic acid, were on average 11% and 16% of the fenbutatin oxide concentration, respectively. As with fenbutatin oxide, there was no significant movement through the soil to lower levels.
The use of computer‐generated electrostatic surface maps for the design of new ‘GABA‐ergic’ insecticides
Authors: Whittle Alan J. , Fitzjohn Stephen , Mullier Graham , Pearson David P. J. , Perrior Trevor R. , Taylor Robin , Salmon Roger
Published: November 2006

A computer model was constructed based on the observation that a number of structurally dissimilar compounds gave rise to similar biological activity. Mode of action work confirmed the link. The model was then used to prioritise targets for synthesis and successfully predicted many active series. The major limitation of the model was that it was unable to predict potency or spectrum. It is thought likely that the factors controlling these limitations are linked with LUMO energies, but this hypothesis has not been proven.
Adsorption and ED50 values of five soil‐applied herbicides
Authors: Pedersen Hanne Juul , Kudsk Per , Helweg Arne
Published: November 2006

The soil partition coefficients (Kd values) and ED50 values of carbetamide, isoproturon, propyzamide, trifluralin and pendimethalin were determined on various soil types. Adsorption increased in the order carbetamide < isoproturon < propyzamide < trifluralin < pendimethalin, whereas the influence of soil types on herbicide efficacy increased in the order isoproturon < carbetamide < pendimethalin < trifluralin < propyzamide. The relationship between adsorption and ED50 values of the herbicides was examined by estimating the herbicide concentration in soil water solution. Adsorption and ED50 values on common Danish soil types (0.6% carbon and 12% clay to 2.3% carbon and 4.4% clay) differed by factors of up to three and four, respectively, indicating a possibility of adjusting the herbicide dose according to soil factors.
Occurrence of organochlorine agrochemical residues in Spanish cheeses
Authors: Bentabol Antonio , Jodral Manuela
Published: November 2006

A total of 146 samples of different kinds of cheeses produced in Spain were analysed in order to ascertain the specific contamination pattern. The organochlorine compounds studied were those most commonly investigated in previous surveys: α‐HCH, β‐HCH, γ‐HCH (lindane), γ‐HCH, chlordane, aldrin, dieldrin, endrin, heptachlor, heptachlor epoxide, and the isomers and metabolites of DDT. α‐HCH, β‐HCH, γ‐HCH, chlordane, p,p′, DDT, and p,p′‐DDE were found in more than 76% of samples; p,p′‐DDE and γ‐HCH were the most frequently detected, with frequencies of 100 and 97.9% respectively. γ‐HCH, aldrin, dieldrin, heptachlor, heptachlor epoxide, o,p′‐DDT, p,p′‐DDD and o,p′‐DDD were observed at lower frequencies. No residues of endrin were detected in any sample. Insecticides exceeding the maximum residue limits (MRLs) were chlordane, β‐HCH, α‐HCH and γ‐HCH, with 42, 20, eight and six samples respectively. Mean residues of organochlorines found were as follows (μ kg−1 butterfat): α‐HCH = 46.3; β‐HCH = 46.5; γ‐HCH = 54.2; δ‐HCH = 16.9; aldrin = 16.7; dieldrin = 9.7; heptachlor = 15.9; heptachlor epoxide = 14.8; chlordane = 50.2; o,p′‐DDT = 5.1; p,p′‐DDT = 12.4; o,p′‐DDT = 19.6; p,p′‐DDD = 46.7; o,p′‐DDE = 6.9; p,p′‐DDE = 40.7 (.DDT = 55.0).

Estimated dietary intakes (EDIs) from cheese consumption were compared to acceptable daily intakes (ADIs) for the pesticides where residues exceeded the MRL. EDIs calculated were in all cases below ADIs, and, therefore, based on the ADIs, there is no health risk involved in the consumption of cheese from Spain arising from organochlorine residues.
Integration of chemical and biological control systems for arthropods: Evaluation in a multitrophic context
Authors: Wright Denis J. , Verkerk Robert H. J.
Published: November 2006

The methods used to evaluate and categorise the effects of pesticides on beneficial arthropods are reviewed, including the potential significance of indirect, ‘sub‐lethal’ activity and the importance of bioavailability of pesticides under semi‐field or field conditions. Interspecific and intraspecific differences in the susceptibility of natural enemies (parasitoids and predators) to pesticides are considered, including the use of resistant strains in Integrated Pest Management (IPM) systems. The potential impact of pesticide resistance in the target pest on its natural enemies is also discussed. The need to assess the influence of the host plant/cultivar on the efficacy of pesticides for use in integrated control programmes (ditrophic effects) and of the possible effects of such chemicals on host plant/cultivar‐pest‐parasitoid systems (tritrophic effects) are then described with specific reference to the diamondback moth and key endolarval parasitoids. Finally, the potential for manipulation of tritrophic interactions to enhance parasitism by application of low doses of toxicants is demonstrated.
Chronic effects of dimethoate on the reproductive potential of the fresh‐water teleost, Clarias batrachus
Authors: Begum Ghousia , Vijayaraghavan Shantha
Published: November 2006

In a study of the fresh‐water teleost Clarias batrachus L., fish were exposed to a commercial 300 g litre−1 EC formulation (of dimethoate at 10.8 mg AI litre−1) for a period of six months extending over prespawning, spawning and postspawning phases of the annual reproductive cycle. A parallel group of fish without dimethoate served as control. Significant reduction in the fecundity pattern of exposed fish was noticed throughout the experimental period. The gonadosomatic indices of both male and female exposed fish were reduced when compared with the control fish. The reduction continued until the termination of the experiment. It was inferred from the present study that, at this level, this pesticide affects the reproductive potential of this fish.
Transformation of aldicarb sulfoxide and aldicarb sulfone in four water‐saturated sandy subsoils
Authors: Smelt Johan H. , Van De Peppel‐Groen Ariette E. , Leistra Minze
Published: November 2006

The transformation of aldicarb sulfoxide and aldicarb sulfone was studied in incubations with water‐saturated subsoils under simulated field conditions at 10°C. The subsoils were collected at four locations from beneath the water table at a depth of 2.5 to 3.5 m. In three of the subsoils, the half‐life of sulfoxide, incubated at concentrations of 0.14‐0.17 mg litre−1, ranged from 0.7 to 2.8 years. At higher concentrations (8‐13 mg litre−1), its half‐life ranged from 3.4 to 6.4 years. At the lower concentration, a large fraction of sulfoxide was transformed into sulfone. The rates of transformation of the sulfone at the lower concentration in the three subsoils corresponded to half‐lives of 3.3 to 8.1 years, but in only one subsoil was a significant transformation rate (half‐life 6.7 years) measured at the higher concentration during the 2.3‐year incubation period. The half‐lives at the lower concentrations were more like those in field studies, and perhaps would still underestimate transformation rates under field conditions. After a year, 2.5‐15% of the higher sulfoxide and sulfone doses had been trapped as [14C] carbon dioxide. In the fourth subsoil, with more anaerobic conditions, the half‐life of sulfoxide at both concentrations was less than 0.02 year and that of sulfone was about 0.04 year. Four or five radio‐labelled transformation products could be traced in this subsoil and about half of the dose of both compounds was trapped as [14C] carbon dioxide.
Metal chelate molluscicides: The redistribution of iron diazaalkanolates from the gut lumen of the slug, Deroceras reticulatum (Müller) (Pulmonata: Limacidae)
Authors: Clark Suzanne J. , Coward Nicola P. , Dawson Glenn W. , Henderson Ian F. , Martin Andrew P.
Published: November 2006

Two related iron chelates, one toxic to slugs by ingestion, the other not, were introduced into the foregut of D. reticulatum. The subsequent movement and redistribution of the metal within the slug tissues was studied by labelling the chelates with the radioactive isotope 55Fe. In slugs which survived treatment approximately half of the 55Fe was voided in faeces. The iron retained became unevenly distributed, the highest concentration occurring in the digestive gland, irrespective of the chelate used. At high doses, slugs treated with tris(1‐oxo‐1,2‐diazabutan‐2‐oxido)Fe(III) were fatally poisoned while those treated with the homologue, tris(1‐oxo‐1,2‐diazaoctan‐2‐oxido)Fe(III) were not. Slugs killed by the toxic chelate consistently contained proportionally less iron in the digestive gland and proportionally more in the body wall and reproductive system. Dosing slugs already killed by carbon dioxide asphyxiation gave a similar pattern, suggesting that the greater mobility of the iron from the toxic chelate was not a function of the slugs' metabolism.
Management of microbial processes in cattle‐dipping vats containing coumaphos
Authors: Karns Jeffrey S. , Ahrens Elmer H. , Davey Ronald B. , Shelton Daniel R.
Published: November 2006

The organophosphate veterinary insecticide coumaphos [O‐3‐chloro‐4‐methyl‐2‐oxo‐2H‐chromen‐7‐yl O, O‐diethyl phosphorothioate] is used by the Animal and Plant Health Inspection Service of the United States Department of Agriculture in its program designed to prevent re‐entry of the southern cattle tick (Boophilus microplus Can.) and the cattle tick (B. annulatus Say) into the United States from Mexico. Large amounts of waste acaricide are generated annually in this program. One event that triggers disposal of coumaphos dips is the accumulation of potasan [O, O‐diethyl O‐4‐methyl‐2‐oxo‐2H‐chromen‐7‐yl phosphorothioate]. This process was shown to occur under anaerobic conditions and to be inhibited by mercury ions, indicating that anaerobic micro‐organisms were responsible for a reductive dechlorination. Maintaining coumaphos suspensions at pH < 7 prevented the reductive dechlorination of coumaphos and left a suspension that was amenable to disposal by biodegradation. A field trial on an 11000‐litre capacity coumaphos dipping vat demonstrated the applicability of using acid to extend the life of coumaphos solutions and of biodegradation for the disposal of spent material.
Improved method for the analysis of imazapyr in soil
Authors: Helling Charles S. , Doherty Michael A.
Published: November 2006

A method for the analysis of imazapyr [2‐(4‐isopropyl‐4‐methyl‐5‐oxo‐2‐imidazolin‐2‐yl)nicotinic acid] residues in tropical and temperate soils was developed. Imazapyr residues, extracted from soil with ammonium hydrogen carbonate and cleaned‐up by centrifuging, anion‐exchange solid‐phase extraction (SPE), pH adjustment, and C18 SPE, were determined by HPLC. Recoveries from soils from Hawaii (Halii sandy clay loam), Texas (Houston Black clay), and Maryland (Codorus loam), USA, fortified with imazapyr (0‐5 μg g−1 soil) and equilibrated for 12‐18 h, were 99(±3)%, 104(±4)% and 89(±2)%, respectively. Recoveries were independent of fortification level, but dependent upon soil type. Methods previously described in the literature produced imazapyr recoveries of less than 60% with Halii soil. This improved method has a limit of detection of 5 ng g−1 (equivalent to or better than other methods) and affords higher recovery of imazapyr residues from tropical soil.
Mode of action of the anilino‐pyrimidine fungicide pyrimethanil. 2. Effects on enzyme secretion in Botrytis cinerea
Authors: Milling Richard J. , Richardson Caroline J.
Published: November 2006

The effect of pyrimethanil on the levels of cell wall degrading enzymes secreted by Botrytis cinerea Pers. was investigated in diseased plant tissues and in liquid B. cinerea cultures. Total proteinase activity isolated from infected carrot slices which were treated with 5.0 μM pyrimethanil was decreased by 76%, 3 d after inoculation. Polygalacturonase, cellulase, proteinase and laccase activities were all decreased in the medium of three day‐old cultures grown in the presence of pyrimethanil. The pyrimethanil concentrations resulting in 50% reduction in total enzyme activities (IC50) were approximately 0.25 μM for polygalacturonase, cellulase and proteinase, and approximately 1.0 μM for laccase. No significant growth inhibition was observed at these pyrimethanil concentrations. Pyrimethanil did not inhibit the enzymes directly, nor did it inhibit the synthesis of cytosolic proteins. Therefore, it was proposed that the fungicide inhibits protein secretion at a post‐translational stage in the secretory pathway.

Large differences were found in the effects of pyrimethanil on the growth of B. cinerea in liquid cultures and on agar plates, depending on the composition of the medium. In liquid media containing cellulose and protein as carbon and nitrogen sources, growth inhibition occurred at 5.0 μM pyrimethanil, whilst no growth inhibition was observed with 50 μM pyrimethanil in malt extract. Similarly, growth occurred on potato/dextrose agar (PDA) at 0.5 μM pyrimethanil, but no growth was seen at this concentration on agars containing cellulose and protein. Thus it appears that pyrimethanil is most active in media where the fungus has to utilise extracellular enzymes to mobilise the nutrients it requires for growth.
Sterol composition and resistance to DMI fungicides in Erysiphe graminis
Authors: Senior Ian J. , Hollomon Derek W. , Loeffler R. S. Thomas , Baldwin Brian C.
Published: November 2006

The effects of the fungicides, flutriafol, triadimenol and an experimental compound (2,2‐dimethyl‐3‐(2‐chlorobenzyl)‐4‐(1,2,4‐triazol‐1‐yl)‐butan‐3‐ol), on conidial viability and lipid composition, have been examined in strains of barley and wheat powdery mildew (Erysiphe graminis DC.) sensitive or resistant to DMI fungicides. In the absence of fungicides, these strains had the same sterol composition, regardless of their sensitivity to DMIs. Following treatment with the compounds, conidia contained eburicol and obtusifoliol, indicating inhibition of the 14α‐demethylase. There was also an accumulation of episterol, suggesting that introduction of the 5,6‐double bond was also inhibited. The changes in sterol composition induced by the fungicides were small. The fatty acid composition of sensitive and resistant strains was also determined. Triadimenol treatment caused an increase in the saturation of C22 and C24 acids in all strains examined, but changes were not correlated with the biological effects of the fungicide. No single mechanism of resistance emerged from the study.