The toxicity of mixtures of a pyrethroid with organophosphorus insecticides to Tetranychus urticae Koch

Laboratory studies of the cotoxicity of a pyrethroid insecticide, fenvalerate, and several organophosphorus insecticides against the two-spotted spider mite, Tetranychus urticae Koch, showed that a useful degree of potientation of toxicity occurred. The most effective combination of fenvalerate and azinphos-methyl was found to be a 1:1 ratio. Phosphates and phosphorodithioates in combination with fenvalerate were more toxic than phosphoromonothioates. The results suggest a practical method of improving the acaricidal activity of pyrethroid insecticides.     

Resistance of Thrips tabaci to pyrethroid and organophosphorus insecticides in Ontario, Canada

Onion thrips, Thrips tabaci Lindeman, were collected from commercial onion fields in 2001, 2002 and 2003 to assess resistance to lambda-cyhalothrin, deltamethrin and diazinon. In 2001, six of eight adult populations were resistant to lambda-cyhalothrin, with resistance ratios (RR) ranging from 2 to 13.1 and four of these were also resistant to deltamethrin, with RR ranging from 19.3 to 120. Three of four adult populations were resistant to diazinon with RR ranging from 2.5 to 165.8. In 2002, four of seven nymphal populations and three of six adult populations were resistant to deltamethrin, with RR ranging from 4.3 to 72.5 and 9.4 to 839.2, respectively. Only one of six nymphal populations and one of five adult populations were resistant to diazinon, with RR of 5.6 and 2.3, respectively. In 2003 diagnostic dose bioassays, 15 of 16 onion thrips populations were resistant to lambda-cyhalothrin and all were resistant to deltamethrin. Eight of the 16 were resistant to diazinon. These results indicate that insecticide resistance is widespread in onion thrips in commercial onion fields in Ontario.     

Pesticide residues in foodstuffs in Great Britain; organochlorine pesticides,organophosphorus pesticides and fumigant residues in home-produced and imported wheat

Residue levels of organochlorine pesticides, organophosphorus pesticides, fumigants and bromide were determined in home-produced and imported wheat during the period October 1978 to April 1979. A total of 281 samples was analysed of which 133 contained low levels of carbon tetrachloride, 112 contained low levels of gamma-HCH and 26 contained low levels of malathion. One sample contained a residue of carbon tetrachloride, and another a residue of 1,2-dichloroethane, both of which were above the Codex Alimentarius guide-line levels. No other residue approached the proposed Codex Alimentarius maximum residue limits.     

Multiple forms of esterases in mouse,rat, and rabbit liver,and their role in hydrolysis of organophosphorus and pyrethroid insecticides

Six to seven esterases from mouse, rat, and rabbit liver microsomes were resolved by chromatofocusing in the pH range 7–4. Each esterase peak showed a different substrate specificity pattern with the substrates evaluated. Malathion and paraoxon hydrolysis always corresponded with p-nitrophenyl acetate and methylthiobutyrate hydrolysis, whereas the pattern of fenvalerate hydrolysis was more complicated. Phosphorotriester hydrolase activity was isolated, and was found to be more specific toward paraoxon than toward the other insecticides. Time-course studies of paraoxon hydrolysis indicated that the hydrolysis of paraoxon by carboxylesterase was an inhibitory reaction. This reaction and phosphorotriester hydrolase activity can serve as a detoxication reaction toward organophosphate insecticides.     

Resistance of Pakistani field populations of spotted bollworm Earias vittella (Lepidoptera: Noctuidae) to pyrethroid,organophosphorus and new chemical insecticides

BACKGROUND: The spotted bollworm Earias vittella (Fab.) is a serious pest of cotton and okra in Pakistan. Owing to persistent use of insecticides, this pest has developed resistance, especially to pyrethroids. The present studies aimed at determining the extent of resistance to pyrethroid, organophosphorus and new chemical insecticides in Pakistani populations of E. vittella. RESULTS: Field populations of E. vittella were monitored at Multan, Pakistan, from 1999 to 2007 for their resistance against six pyrethroid, four organophosphorus and six new chemical insecticides using a leaf‐dip bioassay. Of the pyrethroids, resistance was generally low to zeta‐cypermethrin and moderate to high or very high to cypermethrin, deltamethrin, esfenvalerate, bifenthrin and lambda‐cyhalothrin. Resistance to organophosphates chlorpyrifos, profenofos, triazophos and phoxim was recorded at very low to low levels. Among new chemicals, E. vittella had no or a very low resistance to spinosad, emamectin benzoate and methoxyfenozide, a very low to low resistance to abamectin, a very low to moderate resistance to indoxacarb and a moderate resistance to chlorfenapyr. CONCLUSION: The results indicate a lack of cross‐resistance between pyrethroid and organophosphorus insecticides in E. vittella. Rotation of insecticides showing no, very low or low resistance, but belonging to different insecticide classes with unrelated modes of action, may prevent or mitigate insecticide resistance in E. vittella. Copyright © 2009 Society of Chemical Industry     

Membrane partitioning of organophosphorus and organochlorine insecticides and its implications for mechanisms of toxicity

Partition coefficients of organophosphorus and organochlorine insecticides were determined in several types of membrane. Insecticide partitioning varied among the membranes under study, depending on temperature, cholesterol content and on the physico-chemical profiles of membrane components and the insecticides themselves. The maximal partitions for DDT, lindane, parathion and malathion in egg phosphatidylcholine bilayers over the temperature range from 10 to 37°C (at which the lipid is in the liquid-crystalline state) were about 260000, 2000, 1000 and 120, respectively. Incorporation of 50 mol% cholesterol in egg phosphatidylcholine bilayers dramatically decreased the partition and almost abolished the temperature effect. First-order phase transitions of dimyristoyl-, dipalmitoyl- and distearoylphosphatidylcholines (DMPC, DPPC and DSPC) were accompanied by a sharp increase in insecticide partition. Furthermore, the insecticides under study were more easily accommodated in bilayers of short-aliphatic-chain lipids, since higher values of partition were obtained in DMPC bilayers. Partition values in native membranes depended considerably on the membrane type and composition and were higher in sarcoplasmic reticulum (SR) and mitochondria than in brain microsomes, myelin and erythrocytes. Identical results were obtained in related liposomes of total extracted lipids, although the absolute partitions showed decreased values. In general, the incorporation of insecticides correlated reasonably with the cholesterol content of the membranes. The order of partitioning of the above insecticides did not run parallel with their toxicity to mammals and, both in model and in native membranes, followed the sequence: DDT ? lindane > parathion > malathion.     

The effect of selected uv absorber compounds on the photodegradation of pyrethroid insecticides applied to cotton fabric screens

UV absorber compounds were tested to reduce the photolytic decomposition of deltamethrin, applied to 100 % cotton fabric, to be used as a target screen for tsetse fly control. In the absence of UV absorbers, over 90% of deltamethrin was degraded after 6 h irradiation under an Osram UV-sun radiation lamp (equivalent to 96 h sunlight) at 35(±1)°C. The degree of protection increased with increase in the proportion of the U V absorber compound. With a mixture of 2,4-dihydroxybenzophenone (I) and deltamethrin (3 + 1, by mass) 7% of deltamethrin was degraded. Similarly, I protected alpha-cypermethrin and cyfluthrin against photolysis, I and 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid (IV) both protected deltamethrin from “Glossinex 200” SC formulation against photolysis, but I was more effective than IV.     

Predicting mammalian metabolism and toxicity of pesticides in silico

Pesticides must be effective to be commercially viable but they must also be reasonably safe for those who manufacture them, apply them, or consume the food they are used to produce. Animal testing is key to ensuring safety, but it comes late in the agrochemical development process, is expensive, and requires relatively large amounts of material. Surrogate assays used as in vitro models require less material and shift identification of potential mammalian toxicity back to earlier stages in development. Modern in silico methods are cost‐effective complements to such in vitro models that make it possible to predict mammalian metabolism, toxicity and exposure for a pesticide, crop residue or other metabolite before it has been synthesized. Their broader use could substantially reduce the amount of time and effort wasted in pesticide development. This contribution reviews the kind of in silico models that are currently available for vetting ideas about what to synthesize and how to focus development efforts; the limitations of those models; and the practical considerations that have slowed development in the area. Detailed discussions are provided of how bacterial mutagenicity, human cytochrome P450 (CYP) metabolism, and bioavailability in humans and rats can be predicted. © 2018 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

拟除虫菊酯类杀虫剂对棉铃虫雌蛾化学通讯系统的影响

用低致死剂量（LD30）氰菊酯和氰戊菊酯胸部点滴处理棉铃虫3龄幼虫后，研究拟除虫菊酯类杀虫剂对存活雌蛾化学通讯系统的影响。结果表明，杀虫剂对雌蛾的求偶行为不产生明显影响，对照组和杀虫剂处理组雌蛾的求偶高峰均为第3个暗期的8-8．5h，求偶率均可达73％-82％。氰戊菊酯处理组中雌蛾性信息素各组分滴度和总量与对照无显著性差异，但溴氰菊酯处理组中雌蛾性信息素的主组分Z11-16：Ald和次要组分Z9-16：Ald、Z7-16：Ald的滴度及信息素总量均显著高于对照组，并且两个活性组分Z11-16：Ald和Z9-16：Ald的比例与对照组雌蛾有显著差异。     

Effect of pyrethroid insecticides on EEG activity in conscious,immobilized rats

Preseizure and seizure EEG patterns elicited by the pyrethroid insecticides, deltamethrin and cis-permethrin, were compared in immobilized Sprague-Dawley rats. Deltamethrin (1–3 mg/kg, iv) produced a preseizure EEG pattern of high-amplitude, slow, 2- to 5-Hz synchronized cortical waves or spike-wave complexes. cis-Permethrin (20–40 mg/kg, iv) elicited an immediate EEG change characterized by 6- to 12-Hz high-amplitude waves with intermingled high-voltage spikes. DDT (50–70 mg/kg, iv) produced a sustained EEG activation similar to that seen after cis-permethrin, but of higher frequency. All three insecticides produced generalized EEG seizure activity, but this was more prominently associated with poisoning due to deltamethrin. cis-Permethrin and DDT gave rise to EEG seizures only at lethal doses. Electrodes stereotaxically positioned in ventral hippocampus, caudate, putamen, thalamus, septum, red nucleus, and cerebellum detected no preferential activation of any of these subcortical sites in either preconvulsive or convulsive phases of poisoning. These results indicate that both deltamethrin and cis-permethrin can have marked effects on mammalian EEG activity. This does not support the hypothesis of differing sites of action, i.e., peripheral vs. central, for the two types of compound. The more pronounced seizure-inducing action of deltamethrin may instead reflect a greater efficacy of cyanopyrethroids at target sites within the central nervous system.     

三种有机磷农药胚胎期暴露对新生鼠脑组织结构的影响

探讨了3种常用的有机磷农药胚胎期暴露对新生鼠脑组织结构的影响。在母鼠妊娠期7.5～11.5 d时,连续5 d每天分别经皮下注射2 mg/kg bw的二嗪磷(diazinon)、2 mg/kg bw的毒死蜱(chlorpyrifos)及50 mg/kg bw乙酰甲胺磷(acephate),显微镜下观察并计数大脑皮层S1区胶质细胞和神经元数量及比率,以及海马CA1、CA3区锥体细胞的数量及体积密度。结果表明,二嗪磷与毒死蜱处理分别使得大脑皮层S1区胶质细胞数减少了14.29%和21.43%;毒死蜱处理导致胶质细胞与神经元比率下降了24.19%;二嗪磷与毒死蜱处理后海马CA1区锥体细胞数量分别下降了9.30％与20.93％,毒死蜱处理后锥体细胞体积密度下降了27.05％;二嗪磷与毒死蜱处理后海马CA3区锥体细胞数量分别下降了22.22％和19.44％,锥体细胞体积密度分别下降了23.54％和18.98％;而乙酰甲胺磷对新生鼠大脑皮层与海马细胞均无明显影响。     

The effects of temperature and humidity on the toxicity of three organophosphorus insecticides to adult Oryzaephilus surinamensis (L.)

The toxicities, to a laboratory susceptible strain and to a resistant strain of Oryzaephilus surinamensis (L.), of water-dispersible powder formulations of pirimiphos-methyl, fenitrothion or chlorpyrifos-methyl under constant conditions of 25°C and 70% r. h. were compared to the toxicities when the insects were exposed to a diurnal cycle of 12.5–20–12.5°C and 70–50–70% r. h. to simulate grain store conditions in the UK during spring and autumn. All the insecticides were more effective at 25°C and 70% r. h. The LD₅₀ values for the susceptible strain were low, being 4.4 and 1.4 mg m^?2 at 12.5-20°C and 25°C, respectively, for chlorpyrifos-methyl, 18.3 and 4.1 mg m^?2, respectively, for pirimiphos-methyl, and 4.0 and < 1.O mg m^?2, respectively, for fenitrothion. The LD₅₀ values obtained from the two sets of environmental conditions for a resistant strain (484) differed by factors of 1.8 for chlorpyrifos-methyl, 4.8 for pirimiphos-methyl, and 7.3 for fenitrothion. Toxicity studies were also made with chlorpyrifos-methyl under various constant conditions of temperature and humidity from 5–30°C (5°C intervals) and 30, 50, 70 and 90% r. h., and also at O°C and 60% r. h. Chlorpyrifos-methyl was very effective and there was little or no cross resistance to chlorpyrifos-methyl in the resistant strain. From 15 to 30°C, mortality was high, and differences in mortality at the LD₅₀ level for the various humidities were slight, but there was a decrease in mortality with decreasing humidity at any one temperature, in particular, at 5°C, 50 and 70% r. h., and 10°C and 50% r. h. Chlorpyrifosmethyl was more toxic to both strains at the highest humidity (90%) throughout the whole temperature range. The LD₅₀ values for each strain decreased at each temperature as the water vapour concentration was increased. At O°C and 60% r. h., all the insects from both strains died but the cause of death was not clear.     

杀虫剂对中黑苜蓿盲蝽的毒力测定方法及9种杀虫剂的室内毒力测定

中黑苜蓿盲蝽（Adelphocoris suturalis Jakovlev）目前是河南省关键棉花害虫之一。本文研究了中黑苜蓿盲蝽成虫的日龄、性别、密度和食物的有无对瓶膜法毒力测定结果的影响,确定了农药对中黑苜蓿盲蝽毒力的生物测定方法。将羽化10 d内的成虫（不分雌雄）1～3头装入具有待测药膜的20 mL闪烁瓶中,每瓶加1块四季豆作为食物, 24 h检查死亡率。用此法测定的9种杀虫剂对郑州中黑苜蓿盲蝽种群的毒力为： 毒死蜱>硫丹>氯氟氰菊酯>甲萘威>吡虫啉>高效氯氰菊酯>啶虫咪>抗蚜威>溴氰菊酯,LC50分别为0.275、0.335、8.130、16.782、18.684、23.805、27.767、63.420 μg/mL和68.451 μg/mL。     

Effects of six selected orchard insecticides on Neoseiulus fallacis (Acari: Phytoseiidae) in the laboratory

BACKGROUND: Neoseiulus fallacis (Garman) is a key predator of tetranychid mites in integrated pest management (IPM) programs across Canada. This study identified compounds that would be recommended for tier‐II field evaluations in an IPM program. RESULTS: The overall egg mortality caused by the six insecticides was negligible as it extended from 0 to 12.1%. Imidacloprid was classified as toxic to adults. The label rate was 7.73‐fold the LC₅₀. Thiamethoxam was classified as moderately toxic to adults, and its label rate was 2.87‐fold the LC₅₀. Acetamiprid and spinosad were classified as marginally toxic, and their label rates were respectively 0.99‐ and 0.45‐fold the LC₅₀ for adults. Thiacloprid and methoxyfenozide were virtually innocuous to adults. CONCLUSION: Methoxyfenozide was totally harmless to all stages of N. fallacis, and it would be included in IPM programs immediately. Acetamiprid, spinosad and thiacloprid had varying degrees of mild toxicity to at least one growth stage of the predator. Therefore, they were recommended for tier‐II field testing according to their label claims. Imidacloprid and thiamethoxam were toxic to moderately toxic to adults and had significant adverse effects on fecundity. Therefore, they would be field evaluated only if alternatives were unavailable. Copyright 2010 Crown in the right of Canada. Published by JohnWiley & Sons, Ltd     

蔬菜中13种有机磷农药基质效应研究

有机磷农药在农业生产中广泛应用,用气相色谱法进行农药残留检测容易产生基质效应,影响分析结果的可靠性,为研究用气相色谱法进行农残检测过程中有机磷农药在不同蔬菜中的基质效应,选取瓜类、茄果类、叶菜类3类常见蔬菜和13种有机磷农药进行研究,对影响基质效应的因素采取不同变量法进行分析,得出结论:有机磷农药在叶菜类蔬菜中基质效应最大;含有P=O键农药基质效应更强;基质含量越多基质效应越强,并对在检测如何减少基质效应给出了建议.     

Recent studies on the effects of DDT and pyrethroid insecticides on nervous activity in cockroaches

A summary is given of the results of three sets of electrophysiological experiments on the American cockroach (Periplaneta americana). The effects of DDT and S-bioallethrin [bioallethrin (S)-cyclopentenyl isomer] on single giant axons were studied using the voltage-clamp technique. Whereas both molecules induced long tails of inward (sodium ion) current, the voltage and time-dependency of these tails differed. With DDT, the tail was proportional to the activation of the peak current and decreased with the duration of the pulse, suggesting that the molecules were bound to open sodium channels and delayed their closing. With S-bioallethrin, the voltage dependency of the tail was different from that of the peak current, and the tail current increased exponentially with the duration of the depolarisation, suggesting that the pyrethroid insecticide modified resting (or silent) sodium channels into slowly activating channels. Modified action potentials, mimicking those produced by the two molecules, were computed on the basis of these results. Deltamethrin, one of the most potent pyrethroid insecticides, was applied topically on a leg mechanoreceptor and was found to have little effect on the local ‘receptor potential’ but to inhibit action potential production. The effects of topical applications of deltamethrin on the dorsal part of the abdomen, on nervous activity in the abdominal connectives, were studied under different experimental conditions. The results suggest that the insecticide molecules diffused rapidly through the cuticle, were concentrated in the haemolymph, and eventually reached the central nervous system, where they inhibited nerve activity.     

Action of pesticides on earthworms. Part I: The toxicity of cholinesterase-inhibiting insecticides to earthworms as evaluated by laboratory tests

The action of seven cholinesterase-inhibiting pesticides [aldicarb, carbaryl, carbofuran, oxamyl, paraoxon (diethyl 4-nitrophenyl phosphate) parathion and trichloronate], the organochlorine insecticide, gamma-HCH, and the nematicide potassium N-hydroxymethyl-N-methyl(dithiocarbamate) (PHMD) on four earthworm species was investigated by laboratory toxicity tests. Eisenia foetida was the most tolerant species to the pesticides tested. Aldicarb was the most toxic pesticide to this species, causing severe dehydration prior to death or at sublethal concentrations. Aldicarb was also toxic to the other species (Allolobophora caliginosa, A. chlorotica and Lumbricus rubellus), while oxamyl, the other oxime carbamate, was not toxic to any of them. Carbaryl and carbofuran at low concentrations were lethal to A. caliginosa, A. chlorotica and L. rubellus, but E. foetida could tolerate high concentrations without dying, although low concentrations severely affected its ability to work the soil or to disappear from the soil surface. Paraoxon, parathion, trichloronate and gamma-HCH were moderately toxic with low lethal effect to all species. The ability to work the soil was moderately affected by parathion, trichloronate and gamma-HCH. PHMD was toxic to all the species. The lethal and non-lethal effects of the pesticides are discussed in relation to their possible biochemical mode of action in earthworms, and the data are compared with published information from field trials.     

Polyclonal and monoclonal antibodies specific to the chrysanthemic acid moiety of pyrethroid insecticides

Two polyclonal and two monoclonal antibodies raised against chrysanthemic acid (CAA) were prepared for ELISA of pyrethroid insecticides with the common CAA moiety. The monoclonal antibody KCA226 showed the highest reactivity towards allethrin among the antibodies in C-ELISA, although KCA226 was more sensitive to higher concentrations of methanol than the polyclonal antibodies in ELISA. KCA226 was reacted linearly with allethrin at concentrations ranging from 1 to 10 μg litre^-1 in 0·5% methanol and from 300 to 10000 μg litre^-1 in 30% methanol. KCA226 reacted specifically with the pyrethroid insecticides with the CAA moiety but was much less reactive with CAA itself. These results suggest that C-ELISA based on KCA226 is useful for the assay of pyrethroid residues with the common CAA moiety. © 1998 Society of Chemical Industry