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Background Fall armyworm (FAW), Spodoptera frugiperda (Smith), is an economically important pest worldwide. In this study, we selected a genotype of FAW resistant to chlorpyrifos from a field-collected population, characterized the genetic basis of resistance, evaluated cross-resistance and mechanisms of resistance using synergists. Results The LD50 values of chlorpyrifos for the resistant (Clorp-R) and susceptible (Sus) FAW genotypes were 24.26 and 0.023 μg larva-1 , respectively, representing a resistance ratio >1,050-fold. The LD50 values of chlorpyrifos against heterozygotes were 3.34 and 4.00 μg larva-1 , suggesting that resistance is autosomally inherited. The chlorpyrifos resistance in FAW was influenced by few genes, with the minimum numbers of segregations being 1.74 and 1.88. On chlorpyrifos-sprayed plants and leaves, Clorp-R and heterozygotes genotypes showed >95% and >52% survival, respectively, whereas the Sus genotype had no survival, indicating that the resistance is incompletely dominant at the field rate of chlorpyrifos. The Clorp-R genotype presented some cross-resistance to acephate, but low cross-resistance to thiodicarb, methomyl, chlorfenapyr, flubendiamide, methoxyfenozide, spinetoram, and teflubenzuron. The synergists piperonyl butoxide, diethyl maleate and S,S,S-tributyl phosphorotrithiotate did not have relevant effects on the Clorp-R genotype, suggesting a minor role for metabolic resistance. Conclusions The inheritance of chlorpyrifos resistance in FAW was characterized as autosomal, incompletely dominant and polygenic, with metabolic resistance playing a small role in the detoxification of chlorpyrifos. Low cross-resistance between chlorpyrifos and other Mode of Action (MoA) insecticides occurs in FAW, highlighting the importance of considering the rotation of MoA as a strategy to delay resistance. This article is protected by copyright. All rights reserved.

This study investigated the interactions between insecticides (acephate and indoxacarb) and fungal entomopathogens (Beauveria bassiana [Bals.-Criv.] Vuill. strain B27, Metarhizium anisopliae [Metschn.] Sorokin strain ECS1, and a commercial B. bassiana product, Velifer® Biological Insecticide) for controlling the macadamia seed weevil, Kuschelorhynchus macadamiae Jennings and Oberprieler, in the laboratory and glasshouse. In the laboratory, additive interactions between insecticides at their full field concentrations (776 mg AI/L of acephate and 75 mg AI/L of indoxacarb) and fungal entomopathogens at 107 conidia/ml (ECS1 and B27) or at full field concentration (0.5 ml of Velifer®/L) were seen at 6 days and 12 days post-application. Under the same experimental conditions, synergistic interactions against K. macadamiae were observed 6 days post-application when fungal entomopathogens at 2.5 × 106 conidia/ml or at 25% of full field concentration (Velifer®) were co-applied with insecticides at 25% of their full field concentrations, whilst additive interactions were again observed at 12 days post-application. In the glasshouse, additive interactions between insecticides (at full field concentrations) and fungal entomopathogens (at 107 conidia/ml, or at full field concentration for Velifer®) were obtained at 6 days and 12 days post-application. The results from this study suggest that acephate and indoxacarb have both synergistic and additive effects against K. macadamiae when deployed together with fungal entomopathogens, depending on the initial concentrations of mixture components. Combined application of entomopathogens with compatible insecticides promises to provide more effective management of K. macadamiae than individual chemical applications.

Background Integrating fungal biocontrol agents into crop protection programs dominated by synthetic pesticides is an important first step towards developing an IPM program, however their successful integration relies on an understanding of how their performance may be impacted by the remaining agrochemicals deployed for managing other pests and diseases. In this study we tested ten formulated pesticides used in macadamia production at different concentrations to determine their effects on the germination, mycelial growth and sporulation of Metarhizium anisopliae and Beauveria bassiana in vitro. Further tests with laboratory grade actives of the non‐compatible pesticides were conducted to determine whether any antagonistic effects were caused by the active constituent or by formulation additives. Results At their registered concentrations, formulated trichlorfon, acephate and indoxacarb were compatible with M. anisopliae, whereas B. bassiana showed compatibility with formulated trichlorfon, acephate, indoxacarb, sulfoxaflor and spinetoram. Bioassays using laboratory grade active constituents indicated that the adverse impact of formulated beta‐cyfluthrin on both fungal species and that of formulated methidathion on B. bassiana is probably due to components of the emulsifiable concentrate formulations rather than their active constituents. Diazinon was the only insecticidal active that showed high toxicity to both fungal species. The two fungicides, carbendazim and pyraclostrobin, were toxic to both fungal species at all tested concentrations. Conclusion Our results identify which pesticides used on macadamias in Australia are compatible and incompatible with entomopathogenic fungi. Future studies on pesticides degradation rates will help define the spray intervals required to eliminate these adverse effects.

Background Diagnosis of acute intoxication with organophosphate (OP) or carbamate (CM) pesticides in humans is achieved by measuring plasma butyrylcholinesterase (BuChE) activity. However, BuChE activity is not an ideal biomarker in experimental animal models. The aim of this study was to establish an experimental mouse model for evaluating exposure to OP and CM pesticides by monitoring BuChE activity using chimeric mice in which the liver was reconstituted with human hepatocytes. Results A single oral administration of acephate (300 mg/kg), chlorpyrifos (10 mg/kg), fenobucarb (300 mg/kg) or molinate (250 mg/kg) in chimeric mice led to inhibition of >95%, > 95%, 28% and 60% of plasma BuChE activity after 7, 0.5, 0.5 and 7 h, respectively. Dose-dependent decreases in plasma BuChE activity were also observed for acephate and chlorpyrifos. A 5-day repeated-dose study with 10 or 30 mg/kg acephate found a constitutive reduction in plasma BuChE activity to 80% and 70% of pre-dose levels, respectively. Conclusion Changes in plasma BuChE activity in chimeric mice with humanized liver clearly reflected the exposure levels of OP and CM pesticides. These results suggest that the humanized-liver mouse model may be suitable for estimating levels of exposure to these pesticides in humans. © 2017 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

BACKGROUND Detection of neonicotinoid resistance in populations of tobacco thrips, Frankliniella fusca Hinds, throughout the southeastern USA has motivated an examination of alternative insecticides to control problematic infestations on seedling cotton. The objective of this study was to refine understanding of stage-specific mortality and reduced oviposition of several common insecticides (acephate, abamectin, cyantraniliprole, spinetoram, imidacloprid, imidacloprid+thiodicarb, thiamethoxam) on neonicotinoid resistant and susceptible F. fusca populations under laboratory and field conditions. RESULTS Laboratory studies revealed that the average number of eggs per female and larval or adult survivorship responses differed by insecticide and were dependent on the resistance status of the population. In the presence of neonicotinoids, the resistant F. fusca populations exhibited lower mortality and higher egg counts than the susceptible population. In the field study, similar patterns of oviposition suppression were observed, indicating that some insecticides may impact reproductive rate. CONCLUSION This study shows that insecticides have different effects on F. fusca oviposition events, larval and adult mortality that are dependent on neonicotinoid resistance status. Because insecticides tested in this study have varied activity on specific F. fusca life stages (e.g. oviposition suppression, larvicidal activity, adulticidal activity), knowledge of stage-specific activity can be used to improve control and enhance long-term product stewardship. © 2017 Society of Chemical Industry.

The soybean looper Chrysodeixis includens (Lepidoptera: Noctuidae) is a pest of the soya bean, and increasing populations have been observed on several crops in Brazil. Control of this pest is accomplished using insecticides, particularly with new products recently launched in the market. The effectiveness of these insecticides against C. includens and their impact on natural enemies need further study. Therefore, this study aimed to determine the toxicity of nine insecticides for C. includens and their effects on the Blaptostethus pallescens. Toxicity was increased via the addition of an insecticide synergist, and behavioural changes in Blaptostethus pallescens, an anthocorid predator of C. includens, were assessed. Except for acephate, all other insecticides showed high toxicity to C. includens (mortality >80%). The estimated lethal time (LT50) for C. includens was shorter for methomyl, cartap and spinosad than others six insecticides tested in this work. Chlorantraniliprole, chlorfenapyr, deltamethrin, flubendiamide, indoxacarb and spinosad showed selectivity for the predator B. pallescens and exhibited a lower toxicity to the predator than to C. includens. The detoxifying enzymes monooxygenase and glutathione S-transferase may be involved in the selectivity mechanisms of these insecticides for the predator based on the results obtained with the synergized insecticides. Only the insecticides cartap, indoxacarb and spinosad changed the behaviour of the predator B. pallescens. These three insecticides are repellent, and the predator avoids them. However, the predator tended to remain on the surface treated with flubendiamide longer. Our results suggest that the insecticides chlorfenapyr, chlorantraniliprole, flubendiamide, spinosad and indoxacarb are the most promising compounds for use against C. includens. These compounds also preserve populations of B. pallescens and allow more sustainable integrated pest management programmes.

In this study, a molecularly imprinted capillary monolithic column that can recognize the acephate and phosphamidon was synthesized by the molecular imprinting technique combined with a nonhydrolytic sol–gel process using intermediate 4-(dimethoxyphosphorothioylamino)butanoic acid as the template molecule. The resulting material was characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. The potential of the prepared imprinted monolithic columns used as the stationary phase for capillary electrochromatography (CEC) was evaluated. The effects of operating voltage, pH, and acetonitrile content on the electroosmotic flow of the imprinted monolithic columns were evaluated in CEC. Under optimal conditions, the cucumber and lettuce samples spiked with acephate and phosphamidon were extracted and analyzed by this method with satisfactory recoveries ranging from 79.7 to 94.4%. The relative standard deviation for five replicates of 0.1 mg/L mixed solution of acephate and phosphamidon was in the range of 2.7–4.6%.

BACKGROUND The diamondback moth (DBM), Plutella xylostella, is one of the most harmful insect pests on crucifer crops worldwide. In this study, 19 cDNAs encoding glutathione S-transferases (GSTs) were identified from the genomic and transcriptomic database for DBM (KONAGAbase) and further characterized. RESULTS Phylogenetic analysis showed that the 19 GSTs were classified into six different cytosolic classes, including four in delta, six in epsilon, three in omega, two in sigma, one in theta and one in zeta. Two GSTs were unclassified. RT-PCR analysis revealed that most GST genes were expressed in all developmental stages, with higher expression in the larval stages. Six DBM GSTs were expressed at the highest levels in the midgut tissue. Twelve purified recombinant GSTs showed varied enzymatic properties towards 1-chloro-2,4-dinitrobenzene and glutathione, whereas rPxGSTo2, rPxGSTz1 and rPxGSTu2 had no activity. Real-time quantitative PCR revealed that expression levels of the 19 DBM GST genes were varied and changed after exposure to acephate, indoxacarb, beta-cypermethrin and spinosad. PxGSTd3 was significantly overexpressed, while PxGSTe3 and PxGSTs2 were significantly downregulated by all four insecticide exposures. CONCLUSION The changes in DBM GST gene expression levels exposed to different insecticides indicate that they may play individual roles in tolerance to insecticides and xenobiotics. © 2014 Society of Chemical Industry

The degradation and mineralization of acephate in aqueous solutions by 60Co-γ irradiation were investigated. The acephate was dissolved in different pH buffer solutions and purged for 30 min using anticipate gas. It was found that the degradation ratio of acephate increased gradually with the absorbed dose, and the inorganic ions, SO42−, PO43−, and NH4+, were generated in the irradiated solutions. For the solutions without oxygen, the degradation ratio of acephate in N2-saturated solutions containing t-BuOH was the highest, and that in N2-saturated solutions was higher than that in N2O-saturated solutions. However, the total concentration of inorganic ions in N2O-saturated solutions was higher than that in the other solutions. Moreover, the concentration of NH4+ in N2-saturated solutions containing t-BuOH was larger than that of SO42− and PO43−, whereas in N2- or N2O− saturated solutions, the concentrations of inorganic ions were in the order of SO42− > PO43− > NH4+. In the air-saturated and O2-saturated solutions, it was found that the concentration of inorganic ions generated was in the order of SO42− > PO43− > NH4+. The degradation degree of acephate and the concentrations of inorganic ions in O2-saturated solutions were higher than those in the air-saturated solutions. The result showed that both of the oxidative and reductive radicals could degrade the acephate, and the oxidative could improve the mineralization of acephate. It was further concluded that it was easier for the reductive radicals to attack the bonds around N than other bonds around S and P, and the SC and PS bond are easily attacked by oxidative radicals. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 324–332, 2015

BACKGROUND Laboratory selection is often employed in resistance mechanism studies because field-derived populations commonly do not have high enough resistance for such studies. In the present study, a field-collected Laodelphax striatellus population from eastern China was laboratory selected for chlorpyrifos resistance and susceptibility, and the developed strains, along with a field population, were studied for cross-resistance and resistance mechanisms at biochemical and molecular levels. RESULTS A 158.58-fold chlorpyrifos-resistant strain (JH-chl) and a chlorpyrifos-susceptible strain (JHS) were established after laboratory selection of 25 generations. Cross-resistance to deltamethrin, diazinon, methomyl, carbosulfan, acephate and imidacloprid were detected in JH-chl and a field-collected strain (JHF). Synergism and enzyme activity data suggested potential involvement of P450s and esterases in JH-chl as well as AChE alteration. Furthermore, CYP6AY3v2, CYP306A2v2, CYP353D1v2 and LSCE36 genes were significantly overexpressed in JH-chl (6.87–12.14-fold). Feeding of dsRNAs reduced the expression of the four target genes (35.6–56.8%) and caused significant adult mortality (75.21–88.45%), implying resistance reduction. However, mechanism(s) conferring chlorpyrifos resistance in JHF were unclear. CONCLUSION In contrast to previous reports, multiple overexpressed detoxification genes were potentially associated with chlorpyrifos resistance, as confirmed by RNAi feeding tests. Chlorpyrifos resistance exhibits cross-resistance with insecticides in the same and different classes. © 2013 Society of Chemical Industry

The present study investigated the effect of diphenyl diselenide [(PhSe)2 ] on metabolic disorders induced by acephate acute exposure in rats. We also investigated a possible mechanism of action of (PhSe)2 against hyperglycemia induced by acephate. (PhSe)2 was administered to rats at a dose of 10 or 30 mg/kg by oral gavage (p.o.) 1 hour prior to acephate administration (140 mg/kg; p.o.). Glucose and corticosterone levels as well as the lipid status were determined in plasma of rats. Cardiovascular risk factors and the atherogenic index were calculated. Glycogen levels as well as tyrosine aminotransferase (TAT) and glucose-6-phosphatase (G6Pase) activities were determined in livers of rats. Cerebral acetylcholinesterase (AChE) activity was assayed. Acephate induced an increase in glucose and corticosterone levels as well as in TAT and G6Pase activities. AChE activity was inhibited by acephate. Triglyceride (TG) levels and the cardiovascular risk factor TG/high-density lipoprotein-cholesterol (HDL) were increased by acephate. (PhSe)2 was effective against the metabolic disorders induced by acephate acute exposure in rats.

BACKGROUND: Trunk injections of systemic insecticides were evaluated for the management of avocado thrips. Insecticide residues were quantified in leaves to determine when after treatment, and for how long, toxic concentrations of the insecticides were present. Residues in fruit were quantified to determine whether trunk injection of insecticides might present a greater risk than traditional application methods for contaminating fruit. RESULTS: Residues of imidacloprid and dinotefuran were at least tenfold higher in leaves when trees were treated via trunk injection compared with soil application. Dinotefuran uptake was more rapid than imidacloprid, and no residues were detected within fruit. Acephate was also mobilized very rapidly and gave good control of thrips in bioassays; however, residues of acephate and its insecticidal metabolite methamidophos were detected in the fruit for up to 4 weeks after injection. Avermectin uptake was very slow, and it was ineffective against avocado thrips. CONCLUSIONS: Trunk injections of acephate and dinotefuran permitted rapid uptake into avocados, and they are strong candidates as control methods for avocado thrips. However, residues of organophosphates in fruit could necessitate increased preharvest intervals. Residues of neonicotinoids were below detection limits in fruit, suggesting that neonicotinoids may be the more suitable control option of the two chemical classes. Copyright © 2012 Society of Chemical Industry

Organophosphorous pesticides, commonly used in agriculture for achieving better quality products, are toxic substances that have harmful effects on human health. Recent research on pesticides, especially pesticide mixtures, has shown that they are one of the key environmental health issues. The aim of the present study was to investigate whether dichlorvos, acephate, dimethoate and phorate, either used separately or in combination, can induce oxidative damage in rat livers. The levels of superoxide dismutase, glutathione peroxidase, catalase and lipid peroxidation products (malondialdehyde) were used as criteria. Low, middle and high doses of pesticides in drinking water were continuously administered orally to rats ad libitum for 24 weeks. Results show that the antioxidative defense mechanisms and lipid peroxidation in the rat livers display different responses, depending on the pesticide treatments and doses. The parameters for acephate, dichlorvos, phorate and dimethoate in the low-dose group, and the corresponding low-dose co-treated group were not altered. The oxidative damage in rat livers showed different responses with increasing pesticide dose according to the different pesticide treatments. The combination group of dichlorvos, acephate, dimethoate and phorate displayed different responses compared with the single pesticide-treated group. However, these responses did not constitute the sum of the response produced by each pesticide in the liver.

Degradation of the 3 pesticides (acephate, omethoate, and dimethyl dichloroviny phosphate [DDVP]) by electrolyzed water was investigated. These pesticides were commonly used as broad-spectrum insecticides in pest control and high-residual levels had been detected in vegetables. Our research showed that the electrolyzed oxidizing (EO) water (pH 2.3, available chlorine concentration:70 ppm, oxidation-reduction potential [ORP]: 1170 mV) and the electrolyzed reducing (ER) water (pH 11.6, ORP: -860 mV) can reduce the pesticide residues effectively. Pesticide residues on fresh spinach after 30 min of immersion in electrolyzed water reduced acephate by 74% (EO) and 86% (ER), omethoate by 62% (EO) and 75% (ER), DDVP by 59% (EO) and 46% (ER), respectively. The efficacy of using EO water or ER water was found to be better than that of using tap water or detergent (both were reduced by more than 25%). Besides spinach, the cabbage and leek polluted by DDVP were also investigated and the degradation efficacies were similar to the spinach. Moreover, we found that the residual level of pesticide residue decreased with prolonged immersion time. Using EO or ER water to wash the vegetables did not affect the contents of Vitamin C, which inferred that the applications of EO or ER water to wash the vegetables would not result in loss of nutrition.

A gall midge, Pinyonia edulicola Gagne (Diptera: Cecidomyiidae) causes serious damage to pinyon, Pinus edulis Engelm., in urban areas of Colorado. The gall midges infest developing needles, causing them to grow abnormally into spindle-shaped structures and to drop from the tree at the end of the first year, some five to seven years prematurely. Heavy infestations may result in substantial defoliation. Tests to determine efficacy of several insecticidal materials for control of P. edulicola were conducted in a residential area of Fort Collins during 1981 and 1982. Observations were also made on the population levels of the parasitoid Platygaster sp. (Hymenoptera: Platygasteridae). Sticky traps, plastic collection bags, and periodic observations were used to determine the onset of adult emergence to facilitate timing of application of treatments. The materials tested included acephate, carbofuran, oxydemetonmethyl, dimethoate, and two soap products reported to have insecticidal properties. Results indicate that effectiveness of treatments is dependent upon proper rate, timing, and method of application. None of the materials tested in 1981 reduced the number of midge infested needles. Carborufan, dimethoate and oxydemetonmethyl reduced infestation levels significantly in 1982 trials but differences among those treatments were not significant. Infestation levels on trees treated with acephate and insecticidal soap were not different from the check plots. About 1.7 percent of the midge population was parasitized by Platygaster sp. Zusammenfassung Untersuchungen uber Schlupfen, Parasitierung und Bekampfung der Nadelgallmucke Pinyonia edulicola Gagne an Pinus edulis in Colorado In den Siedlungen von Colorado verursacht die Gallmucke P. edulicola an Pinus edulis erhebliche Schaden, indem sie an den Nadeln spiralformige Verkrummungen und Gallen hervorruft, durch welche die Nadeln 5–7 Jahre zu fruh abfallen. Der Befall kann bis zum volligen Entnadeln gehen. Versuche uber die Wirksamkeit verschiedener Insektizide zur Bekampfung der Gallmucke wurden 1981 und 1982 in Fort Collins durchgefuhrt. Gleichzeitig erfolgten Beobachtungen uber den Parasitoiden Platygaster sp. Zur zeitlichen Festlegung der Bekampfungsaktion wurden Lichtfallen, Plastikbeuten und periodische Beobachtungen uber das Erscheinen der Gallmucke verwendet. Die getesteten Insektizide waren Acephate, Carbofuran, Oxydemetonmethyl, Dimethoate sowie 2 Seifenverbindungen. Die Ergebnisse zeigten, das die Wirksamkeit von der Dosierung, der Methode und dem Zeitpunkt abhing. 1981 konnten die Insektizide die Zahl der befallenen Nadeln nicht verringern. Dagegen reduzierten 1982 Corbofuran, Dimethoate und Oxydemetonmethyl den Befall signifikant. Die zwischen diesen Wirkstoffen bestehenden Unterschiede waren nicht gesichert. Dagegen zeigten die 2 Seifenverbindungen keine Wirkung. Etwa 1,7% der Gallmucken-Population wurde von der Schlupfwespe Platygaster sp. parasitiert.

Esterase assay for the detection of resistance to insecticides in hop aphids Phorodon humuli Schrk. Both the acetylcholinesterase and the total esterase activities were measured colorimetrically in hop aphids Phorodon humuli Schrk. collected from wildhop and from hop plants in a plantation. These carboxylesterases were also examined by electrophoresis. The results were compared with those obtained in bioassays on an artificial diet which contained different concentrations of the insecticides Metasystox and Orthene. An improvement in survival was noted when the composition of the aminoacids in the diet was made comparable to the free amino acid composition in the juice of hop leaves. In aphids from the plantation a weak resistance was detected to Orthene and a medium one to Metasystox. We found a positive correlation between increased carboxylesterase activity and resistance to the insecticides examined. These studies show that the time saving biochemical tests are suitable for rapidly assessing general levels of resistance in field populations of hop aphids. Zusammenfassung An Populationen der Hopfenblattlaus Phorodon humuli Schrk, aus Wild- und Kulturhopfen wurden die Acetylcholinesterase- und die Gesamtesterase-Aktivitat photometrisch bestimmt und zudem wurden die Esterasen elektrophoretisch aufgetrennt. Die Ergebnisse dieser bereits an der Grunen Pfirsichblattlaus Myzus persicae Sulz, erprobten biochemischen Untersuchungen wurden mit Insektizidtesten verglichen. Diese wurden auf einem kunstlichem Nahrmedium durchgefuhrt, welches verschiedene Konzentrationen der Wirkstoffe von Metasystox oder Orthene enthielt. Durch Bestimmen der freien Aminosauren im Pressaft von Hopfenblattern konnte die Aminosaurenzusammensetzung des Nahrmediums optimiert werden. Die Blattlause aus Kulturhopfen zeigten im Vergleich mit Tieren von Wildhopfen gegen Orthene eine schwache und gegen Metasystox eine mittlere Resistenz. Der Vergleich der biochemischen Methoden mit den Biotesten ergibt eine gute Ubereinstimmung zwischen erhohter Gesamtesterase-Aktivitat und Insektizidresistenz. Die zeitsparenden biochemischen Methoden eignen sich also auch bei der Hopfenblattlaus, um rasch einen Uberblick uber das Resistenzverhalten von Populationen zu erhalten.

Bemisia tabaci (Gennadius) is a species complex, and its two most damaging biotypes B and Q are globally distributed pests. Despite increasing biological and economic impacts, little is known about the evolutionary mechanisms that favor their competition with native populations. Here, we investigated the genetic mutations in the P450 gene of the invasive B, Q biotypes and the native Cv population. Four mutations associated with chemical resistance, Pro-Leu, Ala-Ser, Ser-Phe and Trp-Leu, were found in the cytochrome P450 CYP6C and CYP9F genes of the B and Q biotypes. Bioassay results also revealed that both the B and Q biotypes have about 12–47 times more resistance to acephate, beta-cypermethrin, methomyl, and 5–7 times more resistance to imidacloprid insecticide than Cv population. Our results provide a molecular approach for better understanding and monitoring the pesticide resistances of invasive and native B. tabaci populations in China.

Acephate, methamidophos and monocrotophos are insecticides used in oil palm plantations for the control of bagworms and leaf-eating caterpillars. The main purpose of this study was to determine whether the physical refining process at laboratory scale, which simulated the manufacturing process, could remove the residues of these three insecticides in crude palm oil, in the unlikely event that crude palm oil were contaminated with these organophosphorus insecticides. A series of crude palm oil samples spiked with low (0.1 µg/g) and high (1.0 µg/g) levels of these insecticides were subjected to a laboratory-scale physical oil refining process. Oil samples drawn at various stages of the refining process, namely, degumming, bleaching and deodorization, were analyzed using an in-house analytical method. The results obtained from these experiments suggest that the physical refining process is capable of effectively removing residual insecticides from crude palm oil. The final product of crude palm oil refining, the refined, bleached and deodorized palm oil, was found to have no detectable levels of acephate, methamidophos and monocrotophos.

BACKGROUND: High amounts of insecticides are often used in intensive tropical vegetable production systems. Their persistence and residues in vegetables and soils need to be studied to ensure food safety and environmental stability. The dissipation of acephate, chlorpyrifos, cypermethrin and their metabolites was studied in green mustard [Brassica juncea (L.) Coss.] and soils. Two treatments, Impact 75 (acephate) and Agent 505 (cypermethrin plus chlorpyrifos), were applied 4 times at weekly intervals. RESULTS: Dissipation of acephate, chlorpyrifos and cypermethrin in green mustard and topsoils followed first-order kinetics, with half-lives of between 1.1 and 3.1 days in green mustard and between 1.4 and 9.4 days in topsoils (26 °C). Higher vapour pressure of insecticides and higher rainfall appeared to stimulate dissipation from the vegetable, with least effect of rainfall on chlorpyrifos. Dissipation rates in the vegetable were faster or similar (cypermethrin) to rates observed for temperate areas. Preharvest intervals of 13, 4 and 3 days were required for acephate, chlorpyrifos, cypermethrin and their metabolites to comply with the tolerance levels. The pesticide dissipation rates in soils varied by less than a factor of 3 between sites. The metabolites methamidophos and TCP derived from acephate and chlorpyrifos amounted to less than 10 and 25% by mass of the parent compounds in soils. Vegetable shading possibly retarded pesticide degradation in soil. CONCLUSION: The dissipation of pesticides and their metabolites in the vegetable was rapid and faster than the dissipation in temperate climates. The degradation rates of pesticides in the soil were equal to or slightly faster than the degradation rates in temperate soils. Copyright © 2008 Society of Chemical Industry

Efficient chemical control is achieved when insecticides are active against insect pests and safe to natural enemies. In this study, the toxicity of 17 insecticides to the sweetpotato whitefly, Bemisia tabaci (Gennadius), and the selectivity of seven insecticides to natural enemies of this insect pest were evaluated. To determine the insecticide toxicity, B. tabaci adults were exposed to abamectin, acephate, acetamiprid, cartap, imidacloprid, malathion, methamidophos, bifenthrin, cypermethrin, deltamethrin, esfenvalerate, fenitrothion, fenpropathrin, fenthion, phenthoate, permethrin and trichlorphon at 50 and 100% of the field rate (FR), and to water (untreated control). To determine the insecticide selectivity, adults of Encarsia sp., Acanthinus sp., Discodon sp. and Lasiochilus sp. were exposed to abamectin, acephate, acetamiprid, cartap, imidacloprid, malathion and methamidophos at 50 and 100% FR, and to water. Groups of each insect species were exposed to kale leaves preimmersed in each treatment under laboratory conditions. Mortality of exposed individuals was recorded 24 h after treatment. Cartap and imidacloprid at 50 and 100% FR and abamectin and acetamiprid at 100% FR showed insecticidal activity to B. tabaci adults. Abamectin at 50 and 100% FR was the least insecticidal compound to the natural enemies Acanthinus sp., Discodon sp. and Lasiochilus sp. The present results suggest that abamectin at 100% FR may decrease B. tabaci field populations but can still be harmless to predators. Implications of these results within an integrated pest management context are discussed.

A method for the determination of acephate, methamidophos and monocrotophos in oil matrices is described. Pesticide residues in crude palm oil were extracted with acetonitrile, and a clean-up process was performed by cooling the entire extract below 10 °C, followed by a discolouring process using a Carbograph SPE cartridge. The extract was analysed using gas chromatography coupled with a pulsed flame photometry detector. The limit of detection for the method was calculated from regression data, and the recovery test results were in the range of 85–109%.

A susceptible strain of diamondback moth, Plutella xylostella (L.), was used to select for resistance to tebufenozide in the laboratory. After continuous selection with tebufenozide 17 times during 35 generations, a resistant strain was achieved with high resistance to tebufenozide (RR 93.8). Bioassay revealed that this strain showed high cross-resistance to abamectin (RR 35.7), methoxyfenozide (29.1) and JS118 (16.5), and a little to deltamethrin (3.9), but no obvious cross-resistance was found to cypermethrin (1.3), fipronil (1.3), trichlorfon (1.1), chlorfenapyr (1.0), phoxim (0.9) and acephate (0.8). The resistant and susceptible insects had similar development rates, but life table tests indicated that the resistant strain showed reproductive disadvantages, including decreased copulation rate, reproductivity and hatchability. When compared with the susceptible strain, the resistant insects had a relative fitness of only 0.3. This indicated that tebufenozide resistance selected under laboratory conditions had considerable fitness costs in this pest, and therefore rotational use of insecticides without cross-resistance is recommended to delay development of resistance.

We examined the effects of fertilization on population abundance and within-plant distribution of western flower thrips, Frankliniella occidentalis Pergande (Thysanoptera: Thripidae), on potted chrysanthemum, Dendranthema grandiflora (Tzvelev). We also investigated the effects of fertilization on the number of insecticide applications needed to control F. occidentalis on potted chrysanthemum. Under greenhouse conditions, rate of change in population abundance of F. occidentalis increased with fertilization levels from 0 to 100% of the standard fertilization level (375 ppm N) and was four times higher on plants fertilized with the standard level (rate of change = 0.14) than on plants fertilized with 0% during the first 4 weeks after thrips inoculation. Within-plant distribution of F. occidentalis was influenced by the phenology of the plants rather than total nitrogen content of plant tissues. Prior to flower opening, more F. occidentalis were found in the middle region of the plants. When the flowers began to open, more thrips were found feeding inside the flowers than on the leaves. We further showed that production time, the time from transplantation to flower opening, shortened considerably with increased fertilization level. Production time was shortest, 12 weeks, for plants fertilized with 100% of the standard fertilization level. When the fertilization level was reduced to 20%, production time lengthened to 13 weeks. When fertilization level was reduced to 0%, production time lengthened to 14 weeks. Increased fertilization from 0 to 100% of the standard level did not result in higher numbers of insecticide applications. All three insecticides (acephate, bifenthrin, and spinosad) were effective in keeping the thrips infestation below a predetermined level, five thrips per plant, but bifenthrin required the most number of applications to do so. For chrysanthemum, a fast-growing crop and heavy utilizer of fertilizer, fertilization influenced not only the population growth of pest insects but also plant production time. As a result, optimizing fertilization level to reduce pest population growth may be a useful tactic in an Integrated Pest Management program for managing F. occidentalis on potted chrysanthemum. However, the effect of fertilization on production time and plant quality should also be considered when implementing this tactic.

Insecticide resistance monitoring using a Potter precision spray tower with discriminating concentration and log dose probability techniques underpins the Australian insecticide management strategy for Frankliniella occidentalis Pergande. Abamectin, acephate, chlorpyrifos, dichlorvos, dimethoate, endosulfan, fipronil, malathion, methamidophos methidathion, methiocarb, methomyl, pyrazophos and spinosad are recommended for use against F. occidentalis but abamectin, methiocarb and pyrazophos are the only chemicals where insecticide resistance has not been detected. Although not registered, chlorfenapyr was effective against F. occidentalis and should be pursued for that purpose. In contrast, chlorpyrifos, dichlorvos and malathion resistance were detected at low to moderate levels throughout the study period putting their sustainable use for F. occidentalis control in doubt. Although it appears that acephate, dimethoate, endosulfan, fipronil, methamidophos, methidathion and spinosad remain effective, some populations contained a small percentage of thrips that survived exposure to a concentration that killed 100% of the susceptible strain. Subsequent laboratory selection of one such population separately with fipronil and spinosad caused an increase in resistance to these insecticides. These products must now be considered at risk. This is the first report of fipronil or spinosad resistance in populations of F. occidentalis.

Summary Samples of tomatoes, peppers, asparagus, spinach and peaches were exposed to three insecticides (acephate, chlorpyrifos and cypermethrin), three ethylenebisdithiocarbamate fungicides (mancozeb, maneb, propineb) and the tetramethyldithiocarbamate fungicide thiram to study the effect of commercial processing on the residues. In most cases, canning operations led to a gradual decrease in residue levels in the finished products, particularly through washing, blanching, peeling and cooking processes. The results indicated that washing plus blanching led to more than 50% loss in pesticide residues, except for in peaches. Ethylenebisdithiocarbamates (EBDCs) were completely removed from tomatoes and spinach by washing followed by hot water blanching. The total amount of pesticide removed by all of the combined canning operations ranged from 90 to 100% in most products. Pepper retained 61% of chlorpyrifos but these residues disappeared during 3-month storage of finished cans. Acephate showed a surprising tenacity in peaches, as 11% of the original residues were still present in 2-year stored cans.

This study was initiated to determine what residues of six insecticides (organochlorine, organophosphorus and pyrethroids) and four dithiocarbamate fungicides remained on raw agricultural commodities after harvest and to study the effect of the subsequent commercial processing on the residues. Sprayed crops of tomatoes, red peppers, asparagus, spinach, artichokes and peaches harvested after controlled field trials contained residues well below the maximum residue levels, except for lindane in tomatoes and acephate in artichoke. Commercial processing procedures led to large reductions in residue levels in the finished products. Washing removed all residual lindane, chlorpyrifos and cypermethrin from tomatoes. Chlorpyrifos residues were reduced by 67% during wood-fire roasting of peppers, and subsequent peeling removed all the remains. Peeling and blanching of asparagus reduced chlorpyrifos concentrations to undetectable levels. Processing of artichokes eliminated acephate and chlorpyrifos after blanching. Acephate in peaches survived successive processing steps until the final heat process that destroyed remaining residues. The net results can contribute to assure the consumer of a safe wholesome food supply. Copyright © 2004 Society of Chemical Industry

Background Endosulfan is not a restricted use organochlorine insecticide and is currently under re-registration review. In 1993, one confirmed case and one possible case of endosulfan poisoning in agricultural workers occurred in two southeastern states. Methods Two cases of suspected endosulfan poisoning were investigated utilizing record reviews, blood samples, a site visit, and clothing analysis. Results Case 1 was fatal; Case 2 resulted in permanent neurological impairment. Additionally, Case 1 mixed and applied two less toxic pesticides, acephate and maleic hydrazide to tobacco plants. Both farm owners had ample opportunity for endosulfan exposure while mixing concentrated endosulfan with water and applying the solution to tobacco with boom sprayers pulled by tractors. Conclusions Estimates of the absorbed dose of endosulfan were not available because methods to determine actual personal exposure that would be found in fat or tissue samples were not used. Health and safety issues associated with endosulfan require a closer examination. A cooperative multi-disciplinary approach to providing timely accurate education is needed to prevent pesticide poisonings. Am. J. Ind. Med. 39:643–649, 2001. © 2001 Wiley-Liss, Inc.

Insecticides are often implicated in causing outbreaks of the cotton aphid, Aphis gossypii (Glover) (Homoptera: Aphididae), through stimulation of reproduction. In this study we report the sublethal effects of dosages of bifenthrin, acephate, carbofuran or pyriproxifen on cotton aphid reproduction. We could not detect any increase or decrease in the intrinsic rate of increase of cotton aphids exposed to bifenthrin, acephate or carbofuran. However, we did detect some increases in the net reproductive rate of aphids treated with bifenthrin justifying further investigation of the effect on reproduction by this insecticide. Trends based on simple linear regression models suggest that sublethal dosages of bifenthrin or carbofuran have a negative impact on aphid population growth as dosages increase. These data suggest that stimulation of reproduction by these insecticides probably does not play a major role in cotton aphid outbreaks or resurgence. Pyriproxyfen is a juvenoid currently used for control of whiteflies in cotton. It demonstrated significant activity towards cotton aphid reared on treated cotton in our bioassays. Pyriproxyfen caused sterility in most aphids exposed to dosages exceeding 1 ppm, and reduced aphid longevity by approximately 50%. However, it did not appear to greatly influence the reproductive potential or longevity of reproductively mature aphids. A field study indicates that pyriproxyfen affects cotton aphid population structure and may have potential in managing cotton aphid outbreaks. Modifying aphid population structure and growth through the use of juvenoids such as pyriproxifen may prove to be an effective proactive approach to pest control without adversely impacting beneficial organisms or causing pest resurgence.

Severe injury from tobacco thrips [Frankliniella fusca (Hinds)] to seedling peanut (Arachis hypogaea L.) has not been documented to reduce yield and quality. However, thrips injury may be economically important when combined with another factor, such as postemergence herbicide injury. This note reports results of a field experiment in which control of tobacco thrips during an unusually dry early season greatly increased peanut seed yield and quality. 'Florunner' peanut was grown using preplant and postemergence herbicides for weed control. Treatments consisted of an untreated control and four labeled insectiddes applied at planting or soon after crop emergence. Populations of adult tobacco thrips were significantly suppressed by aldicarb [2-methyl-2-(methylthio) propionaldehyde O-(methylcarbamoyl) oxime] ; all insecticides significantly suppressed immature thrips. Aldicarb, the most efficacious insecticide treatment, significantly improved peanut yield by 32% and quality as determined by percentage of total sound mature kernels. All but one of the remaining insecticide treatments significantly improved seed yield, with increases ranging from 9 to 31%. Rainfall was extremely low early in the growing season, and (based on 41 yr of records at the site) drier conditions occur 10% of the time. This is a frequency great enough to matter, but low enough to make further research difficult. The observations reported here suggest that early-season moisture stress intensifies peanut yield and quality losses associated with combined injury from thrips and postemergence herbicides.

A biochemical approach was used to characterize acetylcholinesterase (AChE) insecticide insensitivity in several sweetpotato whitefly (Bemisia tabaci; SPW) populations. Discriminating doses of insecticide were established to differentiate between sensitive and insensitive SPW strains and to genotype individual whitefly. This technique was then used to examine the frequency of insensitive AChE alleles in several SPW populations and to isolate a line homozygous for insensitive AChE from a heterogenous B-type population. Inheritance of putative altered AChE genotypes was consistent with the proposed haplo-diploid status of B. tabaci. This biochemical diagnostic was also employed to determine the role of insensitive AChE in the observed resistance profiles of several laboratory populations subjected to different selection regimes. In keeping with previous studies on insecticide resistance in SPW, resistance does not appear to be uniquely associated with the B-type but rather with SPW populations found in crop systems.

We examined toxicity of acephate to third-instar gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae), under different conditions of administration method, availability of food to larvae during bioassay, host plant, and activity of detoxifying enzymes. Larvae that had been fed field-collected foliage of white alder (Alnus rhombifolia Nutt.) were less susceptible 48 h after treatment with topically applied acephate if they were allowed to continue feeding on foliage during the bioassay period (LD 50 = 60.6 μg/g larva) than if they were not (LD 50 = 13.5 μg/g larva). All surviving larvae were replaced on their original food plant after the 48-h bioassay; of these, 14.4% of the larvae not fed during treatment died before pupation, compared with 1.3% of the larvae fed alder during treatment. The LD 50 obtained for topically treated larvae reared and treated on Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco, (51.1 μg/g larva) was comparable to that obtained for larvae fed alder (60.0 μg/g larva) throughout treatment. Larvae treated orally with acephate, however, were slightly more susceptible when reared on Douglas-fir (LC 50 , 20.3 ppm) than when reared on alder (LC 50 , 27.0 ppm). Post-treatment mortality in orally treated larvae was 10.3% in those fed alder and 9.5% in those fed Douglas-fir. Higher cytochrome P-450 activities in larvae reared on Douglas-fir apparently did not enhance tolerance to acephate. Both sexes of orally treated larvae took significantly longer to pupate than did controls on both foliage types, as did topically treated males fed Douglas-fir. Pupal weight generally was slightly, but not always significantly, higher in treated than untreated larvae under all dietary and treatment regimes.

In this study, a novel molecularly imprinted polymer was synthesized using acephate as the template molecule, methacrylic acid as the functional monomer, and ethylene glycol dimethacrylate as the cross-linker. The imprinted polymer was characterized by the static adsorption experiments, and results showed that it had higher adsorption capacity toward acephate and methamidophos than the nonimprinted polymers. Competitive experiments indicated that this material exhibited low selective recognition properties toward acephate in aqueous solution. This prepared material also offered fast kinetics for the adsorption of acephate. After shaking for 90 min, an adsorption capacity of 9.54 mg/g was obtained, and it almost reached the adsorption equilibrium within 120 min. © 2013 Wiley Periodicals, Inc. Adv Polym Technol 2013, 32, 21357; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21357

The freshwater mussel Elliptio complanata and the Asiatic clam Corbicula fluminea were exposed for 96 h at 21°C to aldicarb, a carbamate pesticide, and acephate, an organophosphate pesticide. Test pesticide concentrations ranged from 0 to 320 mg/L. We found no mortality under these conditions. Relative to controls, cholinesterase (ChE) activity in adductor muscle from E. complanata was significantly depressed at concentrations as low as 0.1 mg aldicarb/L and 1.3 mg acephate/L. Higher pesticide concentrations were required to inhibit ChE activity in whole bodies of C. fluminea than in adductor muscle of E. complanata. Raising the experimental temperatures from 21 to 30°C increased pesticide-induced mortality, with mussels dying at aldicarb or acephate concentrations of only 5 mg/L. Cholinesterase activities of adductor muscle depressed 94 to 96% relative to controls began to recover within 2 and 12 d, but they were not fully recovered for 12+ and 24+ d following aldicarb and acephate exposures. Both aldicarb and acephate at 5 mg/L reduced shell closure responsiveness of mussels, with more pronounced effects observed at 27°C than at 21°C. Our data support the usefulness of determining ChE activity in adductor muscle to identify the exposure of freshwater mussels to ChE-inhibiting pesticides.

Peanut (Arachis hypogaea L.) can tolerate severe early-season injury by tobacco thrips [Frankliniella fusca (Hinds)], and controlling populations usually is not recommended the southeastern USA. Field observations, however, indicated that injury from early-season thrips infestation may exacerbate thatinjury caused to peanut by early postemergence herbicide application. Studies were conducted near Jay and Marianna, FL, during 1989 and 1990 to evaluate the interaction between peanut cultivar, preplant incorporated application of vernolate (S-propyl dipropylcabamothioate), postmergence application of alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide] plus paraquat(1,l'-dimethyl-4,4'-bipyridinium oin) and thrips suppression with foliar application of acephate (O,S-dimethyl acetylphosphoroamidothioate). ‘Southern Runner’ was more susceptible than ‘Florunner’ to early-season stress from insect and herbicide injury. Injury from preplant incorporated herbicide alone, postemergence herbicide alone, or thrips alone usually was not sufficient to cause long-term damage to peanut growth or to adversely affect peanut maturity or yield.When two or all of these factors impacted peanut simultaneously, however, delays in crop maturity and reduced yields (up to 11%) were often observed. Early-season suppression of tobacco thrips often alleviated the detrimental effects to peanut. Suppression of thrips populations should receive greater consideration in future integrated pest management programs of peanut to avoid interactions with early-season herbicide stress, especially when growing Southern Runner. Florida Agric. Exp. Stn. J. Ser. no. R-04539.

Sublethal effects of acephate (an organophosphate) and biphenate (a pyrethroid) on greenhouse whitefly (Trialeurodes vaporariorum Westw.) were investigated by measuring male and female longevity, daily rate and lifetime fecundity per female, and egg viability for cohorts exposed to LC 50 s when Acala SJ-2 cotton was a host. Males T. vaporariorum were more sensitive to sublethal concentrations than females. Significant reductions in male longevity were caused by exposure to acephate and biphenate, whereas female longevity was not significantly affected by exposure. Exposure to biphenate and acephate treatments reduced lifetime fecundity by 29% and 37%, respectively. Viability of eggs laid by treated females was not affected. Analysis of patterns and heterogeneity of reproduction suggests that timing and magnitude of oviposition, average level of daily oviposition and reproductive decline were influenced by sublethal concentrations of insecticides. Results of repeated-measures analysis of variance confirmed reductions in fecundity of females T. vaporariorum exposed to sublethal concentrations

A linear relationship (r2 = 0.99) was found between the concentration of acephate in the nutrient solution applied to gerberas (Gerbera jamesonii H. Bollus ex Hook. f) grown in perlite and the mortality of nymphs of greenhouse whitefly, Trialeurodes vaporariorum Westwood. The LD50 for this method of application was 84 mg litre−1. A single irrigation with 180 mg litre−1 acephate killed all nymphs in 10 days without apparent damage to plants. At 120 mg litre−1, acephate accumulated readily in leaves, reaching a maximum concentration of 11 mg kg−1 dry matter on the third day of treatment. Concentrations in leaves then fell gradually, reaching 50% of the maximum concentration seven days later. Methamidophos was first detected in leaves approximately a day later than acephate. A maximum concentration of 9 mg kg−1 dry matter was recorded on day 5 after which the concentration slowly fell. The half-life of methamidophos was estimated to be 11 days. The systemic use of acephate for the control of greenhouse whitefly and its relevance to Integrated Pest Management (IPM) programmes for pests of ornamental plants are discussed.

Sublethal responses of the fish Oncorhynchus mykiss, Galaxias maculatus, Pseudaphritis urvillii, and the crustacean Paratya australiensis to short-term exposures to low concentrations of seven pesticides were compared under identical conditions. Parameters examined were hematocrit, leucocrit, plasma glucose, plasma protein, plasma chloride, muscle RNA and DNA, brain and muscle acetylcholinesterase activity, hepatic glutathione-S-transferase activity, hepatic glutathione, and somatic growth. The organisms were exposed to the following materials–the organophosphate insecticides acephate and fenitrothion; the phenoxyacetate herbicide MCPA-Na; the triazine herbicides atrazine and cyanazine; the fungicide chlorothalonil, and the pyrethroid insecticide cypermethrin–as purified active ingredients in continuous flow through at constant temperature (12–15°C) for 10 or 20 d, with feeding, at five concentrations. Oncorhynchus mykiss was marginally the most sensitive fish species studied in terms of the number of responses to pesticide exposure, but not in terms of the LOECs. Interspecies comparisons indicated that water quality criteria based on juvenile Oncorhynchus mykiss toxicity data alone would not be suitable for the protection of juvenile and adult Galaxias maculatus and Pseudaphritis urvillii from physiological stress in at least three of seven cases. Four of seven maximum acceptable toxicant concentrations (MATCs) derived from physiological responses of fish species resulted from data on Galaxias maculatus and Pseudaphritis urvillii alone. In the case of organophosphates, the decapod crustaceans Paratya australiensis and Astacopsis gouldi were by far the most sensitive. Tentative water quality criteria for the protection of study species from short-term stress are proposed.

Susceptibility to acephate, methomyl, and permethrin was determined with laboratory bioassays of field-collected adults from 15 populations of the B biotype of sweetpotato whitefly, Bemisia tabaci (Gennadius) (Homoptera:Aleyrodidae), from Hawaii. Comparisons at the LC50 showed up to 24-fold resistance to acephate, 18-fold resistance to methomyl, and 4-fold resistance to permethrin. Analysis of variance showed significant intra-island variation in susceptibility to each insecticide, but no significant variation among islands. Insecticide use varied from 4 to 103 insecticide sprays per site per season. Acephate and methomyl were used more often than permethrin. The frequency of application and LC50 for each insecticide were positively correlated across sites. These results suggest that local variation in insecticide use was a primary cause of variation in susceptibility. If local insecticide use is a key determinant of resistance, as our results suggest, growers can retard resistance development locally by reducing their own insecticide use.

Pyrethroid esterases of Trichoplusia ni, Spodoptera littoralis and Bemisia tabaci hydrolyze the trans-isomers of various pyrethroids more extensively than the cis-isomers. Profenofos fed to T. ni larvae at a level inhibiting the gut pyrethroid esterases by 65% with trans-permethrin and of 95% with cis-cypermethrin increased the toxicity of topically applied trans-permethrin by fourfold and cis-cypermethrin by 20-fold. Similar assays with S. littoralis resulted in an increase of about threefold in the toxicity of both compounds. Monocrotophos, profenofos, acephate, and methidathion inhibited pyrethroid esterase activity in B. tabaci and synergized considerably the toxicity of cypermethrin. The remarkable tolerance of the predator Chrysopa carnea to pyrethroids is attributed to the presence of a high level of pyrethroid esterase activity with a unique specificity for hydrolyzing the cis-isomer. Phenyl saligenin cyclic phosphonate, a potent inhibitor for larval pyrethroid esterases synergized the toxicity of trans-permethrin by 68-fold from an LD50 of 17,000 micrograms/g to 250 micrograms/g. In contrast, oxidase inhibitors such as piperonyl butoxide, SV-1, and MPP synergized considerably the toxicity of pyrethroids in Tribolium castaneum and Musca domestica. Hence the predominant pathway for pyrethroid detoxification in insects, whether hydrolytic or oxidative, depends largely on the insect species. The high toxicity of the recent developed acylureas results from their high retention in the insects. Assays using radiolabeled diflubenzuron and chlorfluazuron applied to fourth instar T. castaneum larvae revealed a rapid elimination of diflubenzuron (T1/2 approximately equal to 7 h) as compared with chlorfluazuron (T1/2 > 100 h). Addition of 100 ppm DEF to the diet increased both the retention time and the toxicity of diflubenzuron in both T. castaneum and S. littoralis, which was due probably to the inhibition of diflubenzuron hydrolase activity. Esterases, hydrolyzing pyrethroids, and acylureas may serve as tools for evaluating potential synergists and for monitoring resistance in various agricultural pests due to increased metabolism.

Susceptibility to acephate, methomyl, and permethrin was determined with laboratory bioassays for adults of greenhouse whitefly, Trialeurodes vaporariorum Westwood, from 12 to 14 sites in Hawaii. Comparisons at LC50 showed up to 42-fold resistance to acephate, 36-fold resistance to methomyl, and 8-fold resistance to permethrin. Higher levels of resistance to acephate and methomyl than to permethrin are consistent with greater use of organophosphates and carbamates than pyrethroids by growers. Insecticide use varied from 1 to 98 insecticide sprays per site per season. Significant positive associations between LC50 for each insecticide and frequency of application of the same insecticide were found across sites. This finding suggests that local variation in insecticide use was an important cause of variation in susceptibility.

A semi-micro method is described for monitoring levels of acephate (O, S-dimethyl acetylphosphoramidothioate) and its principal metabolite, methamidophos (O, S-dimethyl phosphoramidothioate) in leaf material derived from treated, hydroponically grown gerberas (Gerbera jamesonii H. Bollus, ex Hook. f.) To minimise injury to the living leaf, analyses were performed on 13-mm diameter discs punched from the interveinal regions of the lamina. The leaf disc samples were then extracted with ethyl acetate. Clean-up of extracts was accomplished by passing the filtered leaf extracts through glass mini-columns containing carbon + filter aid (2 + 5 by mass). Acephate and methamidophos were eluted from the column with methanol and measured simultaneously by programmed temperature gas chromatography using a thermionic specific detector.

Resistance to three organophosphate and four pyrethroid insecticides was monitored from 1992 to 2000 in field populations of adult whiteflies, Bemisia tabaci, from Pakistan using a leaf-dip method. There was generally a very high resistance to dimethoate and deltamethrin, and a moderate resistance to monocrotophos during 1992 to 1996. From 1997 to 2000, resistance to these insecticides dropped to low levels because of less reliance on them for whitefly control, and introduction of new chemistries with novel modes of action that had no cross-resistance to conventional insecticides. Concurrently, whitefly resistance to acephate, fenpropathrin, lambda-cyhalothrin and bifenthrin mostly remained low. An insecticide resistance management strategy is recommended that particularly emphasizes the rotation of still-effective insecticides from different chemical classes along with the use of novel chemicals and other tactics of integrated pest management. (C) 2001 Society of Chemical Industry.

Uptake and translocation of 26 chemicals (herbicides, fungicides, growth regulators, insecticides and model compounds), formulated with and without 'Ethylan TU' (NP8) surfactant, have been determined 24, 48 and 72 b after spraying onto leaves of maize, rape, strawberry and sugar beet. Eight of the chemicals may be classified as polar (log partition coefficient (P) < 0) and 18 as lipophilic (log P 0.8-4.6). Chemicals penetrated more readily into waxy leaves of rape and strawberry than into less-waxy sugar beet, whilst lowest rates were observed for maize. Rates of uptake varied from exceedingly low (< 2% 72 h after application) for uracil, maleic hydrazide, isoproturon and methyl phenylurea applied to maize, to rapid (> 98% within 24 h of application) for acephate and triadimefon applied to strawberry leaves. The effects of NP8 on rates of chemical uptake were classified into 4 types, viz:-(i) low rates, with limited enhancement by NP8; (ii) high rates unaffected by NP8; (iii) marked enhancement by NP8 within 24 h; and (iv) continuous enhancement by NP8 over 0-72 h. Translocation into the tissues immediately adjacent to the target site was greater for waxy than less-waxy plants, enhancement by NP8 was attributed to its effects on penetration rather than to surfactant interactions at the sub-cuticular level. Logarithms of physicochemical properties (partition coefficient, water solubility S, molecular weight MW), together with deposit area and melting point (m.p.) values were used to investigate relationships with uptake and translocation. In most cases the variability could not be described adequately in a simple linear form. Regressions using the entire group of 26 chemicals also showed poor correlations between uptake patterns and individual variables. Polynomials in log S, log P, log MW and m.p. were used to test for complex relationships. A quadratic polynomial in log P, log S and m.p. accounted for slightly more (77%) of the variability between the means for total uptake than a cubic polynomial in log P and log S (75%). Although both regressions were significant, the 'lack of fit' indicated that other factors need to be included to account fully for the variability in rates of uptake and translocation.

Acetylcholinesterase (AChE) activity was measured in Daphnia magna that had been exposed to four organophosphates (OPs; parathion, chlorpyrifos, malathion, and acephate) and one carbamate (propoxur) for 48 h. These results were related to acute toxicity (median effective concentration [EC50] for immobility). For the four OPs, the EC50s were 7.03 pM, 3.17 pM, 10.56 pM, and 309.82 microM, respectively. The EC50 for propoxur was 449.90 pM. Reduction in AChE activity was directly related to an increase in immobility in all chemicals tested. However, the ratio between the EC50 and the AChE median inhibiting concentration ranged from 0.31 to 0.90. A 50% reduction in AChE activity generally was associated with detrimental effects on mobility. However, for acephate, high levels of AChE inhibition (70%) were observed in very low concentrations and were not associated with immobility. In addition, increasing the concentration of acephate further had a slight negative effect on AChE activity but a strong detrimental effect on mobility. Binding sites other than AChE possibly are involved in acephate toxicity to D. magna. Our findings demonstrate different associations between AChE inhibition and toxicity when different chemicals are compared. Therefore, the value of using AChE activity as a biomarker in D. magna will be dependent on the chemical tested.

Migratory white-throated sparrows (Zonotrichia albicollis) were exposed to acephate (acetylphosphoramidothioic acid O, S-dimethyl ester), an organophosphorus pesticide, to determine its effects on migratory orientation and behavior. Birds were also exposed to polarizer sheets to determine the mechanism by which acephate may affect migratory orientation. Adult birds exposed to 256 ppm acephate a.i. were not able to establish a preferred migratory orientation and exhibited random activity. All juvenile treatment groups displayed a seasonally correct southward migratory orientation. We hypothesize that acephate may have produced aberrant migratory behavior by affecting the memory of the migratory route and wintering ground. This experiment reveals that an environmentally relevant concentration of a common organophosphorus pesticide can alter migratory orientation, but its effect is markedly different between adult and juvenile sparrows. Results suggest that the survival of free-flying adult passerine migrants may be compromised following organophosphorus pesticide exposure.

Cholinesterase activity measurements for 542 California agricultural pesticide applicators under medical supervision during the first 9 months of 1985 were analyzed. Twenty-six workers, 4.8% of the sample, had cholinesterase values at or below the California threshold values for removal from continued exposure to cholinesterase-inhibiting pesticides (60% of baseline for red blood cell cholinesterase and 50% of baseline for plasma cholinesterase activity). Eight of these 26 workers, 31.5%, had pesticide-related illnesses. Pesticides most frequently associated with cholinesterase depressions exceeding California threshold values included mevinphos (Phosdrin), oxydemeton methyl (Metasystox-R), methomyl (Lannate), and acephate (Orthene); these pesticides included organophosphates in toxicity categories I and II and one carbamate in toxicity category I.