Toxicity of chlordimeform and amitraz to the egyptian cotton leafworm (Spodoptera littoralis) and the tobacco budworm (Heliothis virescens)

The relative toxicity (μg a.i. g^?1 body wt) of the formamidine insecticide chlordimeform (CDM) and the triazapentadiene insecticide amitraz was examined in two species of noctuid moth Spodoptera littoralis and Heliothis virescens. When applied topically, there was an unexpected and marked difference in the toxicity of CDM base and its hydrochloride to adults of both species, the salt being appreciably more toxic. For H. virescens at least, this difference in toxicity could not be explained by differences in penetration. This trend was reversed for larval instars of S. littoralis; while there was relatively little difference in the toxicity of the base to adult and larval stages, the salt was at least 1000-fold more toxic to adults than to larvae. N¹-Demethylchlordimeform (DCDM) was the only metabolite of CDM to show biological activity against either species, but was much less toxic than the parent compound. Amitraz was far less toxic than either CDM or DCDM; like the CDM salt, it appeared to be more toxic to adult than larval stages of S. littoralis. Application of piperonyl butoxide significantly increased the toxicity of the CDM salt, DCDM and amitraz to adult H. virescens, the synergist being particularly effective with DCDM and amitraz. In contrast, piperonyl butoxide had no significant effect on the toxicity of DCDM, and slightly antagonised the toxicity of DCDM to fourth-instar larvae of S. littoralis.     

Toxicological and biochemical characterization of coumaphos resistance in the San Roman strain of Boophilus microplus (Acari: Ixodidae)

The San Roman strain of the southern cattle tick, Boophilus microplus, collected from Mexico was previously reported to have a high level of resistance to the organophosphate acaricide coumaphos. An oxidative detoxification mechanism was suspected to contribute to coumaphos resistance in this tick strain, as coumaphos bioassay with piperonyl butoxide (PBO) on larvae of this resistant strain resulted in enhanced coumaphos toxicity, while coumaphos assays with PBO resulted in reduced toxicity of coumaphos in a susceptible reference strain. In this study, we further analyzed the mechanism of oxidative metabolic detoxification with synergist bioassays of coroxon, the toxic metabolite of coumaphos, and the mechanism of target-site insensitivity with acetylcholinesterase (AChE) inhibition kinetics assays. Bioassays of coroxon with PBO resulted in synergism of coroxon toxicity in both the San Roman and the susceptible reference strains. The synergism ratio of PBO on coroxon in the resistant strain was 4.5 times that of the susceptible strain. The results suggested that the cytP450-based metabolic detoxification existed in both resistant and susceptible strains, but its activity was significantly enhanced in the resistant strain. Comparisons of AChE activity and inhibition kinetics by coroxon in both susceptible and resistant strains revealed that the resistant San Roman strain had an insensitive AChE, with a reduced phosphorylation rate, resulting in a reduced bimolecular reaction constant. These data indicate a mechanism of coumaphos resistance in the San Roman strain that involves both insensitive AChE and enhanced cytP450-based metabolic detoxification.     

An Example of Cross-resistance to Pyrethroids in DDT-resistant Aedes aegypti

Comparisons of the susceptibility of several strains of adult Aedes aegypti were made. Mosquitoes from Bangkok and Jakarta were found to be highly resistant to DDT and resistant to pyrethroids relative to a laboratory strain. A strain from Singapore, where less DDT has been used, was susceptible to DDT and pyrethroids. Two strains from the Caribbean had LC₅₀ values to DDT 3 times that of the reference strain while the LC₅₀ values against bioresmethrin synergised with piperonyl butoxide were 1 1/2 times raised. Another two strains from central Africa were 2 times tolerant of DDT and 1 1/2 times tolerant of bioresmethrin plus piperonyl butoxide. Agents which block DDT-dehydrochlorinase, esterases and oxidases each caused small increases in the mortality of the Bangkok strain due to DDT and bioresmethrin as well as augmenting toxicity to the susceptible reference strain. It is tentatively suggested that resistance in the Bangkok strain is due to a combination of the actions of these and perhaps other resistance mechanisms.     

Toxicity of spinosad to susceptible and resistant strains of house flies,Musca domestica

The toxicity of spinosad, a new insecticide derived from the bacterium Saccharopolyspora spinosa, was evaluated against susceptible and resistant strains of house fly (Musca domestica L.). Spinosad was highly toxic to house flies based on 72-h LD₅₀ values and the symptoms of poisoning were consistent with a neurotoxic mechanism of action. Spinosad was relatively slow acting, with the maximum toxicity noted at 72 h. Piperonyl butoxide and S,S,S,-tribu-tylphosphorotrithioate synergized the toxicity of spinosad by 3·0- and 1·8-fold, respectively, while diethyl maleate had no significant effect. These results suggest that there is a small degree of monooxygenase-mediated spinosad detoxification in house flies, while hydrolases may be only minimally important and glutathione transferases may have no role. There were no substantial levels of cross-resistance detected, except in the LPR strain where a low 4·3-fold cross-resistance was observed. The cyclodiene-resistant OCR strain was 2·7-fold more sensitive to spinosad than the susceptible strain (CS). These results suggest that cross-resistance may not be a limiting factor for the use of spinosad against house flies. © 1998 Society of Chemical Industry     

三株球孢白僵菌对草地贪夜蛾的毒力比较

为筛选有效防治草地贪夜蛾Spodoptera frugiperda的微生物制剂,采用室内生物测定法测定从北京市、浙江省和海南省土壤样品中分离获得的3株球孢白僵菌Beauveria bassiana菌株bbbj、bbzj和bbhn对草地贪夜蛾3龄幼虫的毒力,并比较这3株菌株的产孢情况和合成白僵菌素的能力。结果显示,分离自北京市的菌株bbbj对草地贪夜蛾3龄幼虫的毒力最强,LC50为3.37×105个孢子/mL;其次为浙江省的菌株bbzj,毒力略逊于菌株bbbj;海南省的菌株bbhn毒力最弱,其在试验最高浓度108个孢子/mL处理7 d后对草地贪夜蛾3龄幼虫的致死率低于50%。菌株bbbj的产孢量远高于另外2株菌株,并且其菌丝结构上着生大量芽生孢子簇,而且菌株bbbj菌体中的白僵菌素含量最高,培养5 d后,分别为菌株bbzj和bbhn的40.08倍和65.85倍。虽然补充白僵菌素可以提高菌株bbhn的毒力,但是草地贪夜蛾幼虫对白僵菌素敏感度不高。表明球孢白僵菌菌株bbbj对草地贪夜蛾幼虫有较高的毒杀活性,具有作为草地贪夜蛾生防菌株的潜力。     

Juvenile hormone analogs: Toxicity and cross-resistance in the housefly

The toxicity of several juvenile hormone analogs (JHAs) to susceptible and insecticide-resistant housefly (Musca domestica L.) strains was determined by an assay procedure in which larvae were exposed to residues of JHAs in glass vials. All JHAs tested were toxic and the most active compound, isopropyl 11-methoxy-3, 7, 11-trimethylododeca-2, 4-dienoate, was 100 times as toxic to the susceptible Orlando Regular strain as methyl parathion and 600 times as toxic as DDT.A 5- to 30-fold tolerance to the different JHAs was present in an insecticide resistant strain in which resistance is associated with a high level of NADPH-dependent microsomal oxidase activity controlled by a gene(s) on chromosome II. Cross-resistance was less marked in a strain with a chromosome V high oxidase gene and absent in strains with other resistance mechanisms.The data indicate that cross-resistance to JHAs in insects may occur in certain strains with high levels of oxidative detoxifying activity. Even so, the most active JHA was far more toxic to both susceptible and resistant strains than methyl parathion or DDT.     

Mechanisms of resistance to diflubenzuron in the house fly, Musca domestica (L.)

The mechanisms of resistance to the chitin synthesis inhibitor diflubenzuron were investigated in a diflubenzuron-selected strain of the house fly (Musca domestica L.) with > 1000 × resistance, and in an OMS-12-selected strain [O-ethyl O-(2,4-dichlorophenyl)phosphoramidothioate] with 380 × resistance to diflubenzuron. In agreement with the accepted mode of action of diflubenzuron, chitin synthesis was reduced less in larvae of the resistant (R) than of a susceptible (S) strain. Cuticular penetration of diflubenzuron into larvae of the R strains was about half that of the S. Both piperonyl butoxide and sesamex synergized diflubenzuron markedly in the R strains, indicating that mixed-function oxidase enzymes play a major role in resistance. Limited synergism by DEF (S,S,S-tributyl phosphorotrithioate) and diethylmaleate indicated that esterases and glutathione-dependent transferases play a relatively small role in resistance. Larvae of the S and R strains exhibited a similar pattern of in vivo cleavage of ³H- and ¹⁴C-labeled diflubenzuron at N₁C₂ and N₁C₁ bonds. However, there were marked differences in the amounts of major metabolites produced: R larvae metabolized diflubenzuron at considerably higher rates, resulting in 18-fold lower accumulation of unmetabolized diflubenzuron by comparison with S larvae. Polar metabolites were excreted at a 2-fold higher rate by R larvae. The high levels of resistance to diflubenzuron in R-Diflubenzuron and R-OMS-12 larvae are due to the combined effect of reduced cuticular penetration, increased metabolism, and rapid excretion of the chemical.     

Synergism of insecticidal action and effects on detoxifying enzymes in vivo of lambda-cyhalothrin and malathion by some nitrogen heterocycles in resistant and susceptible strains of Tribolium castaneum

The interactions of the synthetic pyrethroid, lambda-cyhalothrin and malathion were studied with purines, pyrimidines, caffeine and some other related nitrogenous compounds in resistant and susceptible strains of Triboliurn castaneum (Herbst.) The results were compared with those obtained with a known synergist, piperonyl butoxide (PBO) and precocene I. Adenine, cytosine, guanine, thymine and uracil synergised lambda-cyhalothrin, especially in the susceptible strain, with maximum effect at a 1:1 mass ratio, with the effect decreasing with increasing proportion of the heterocycle. The order of synergism of lambda-cyhalothrin was; precocene I > PBO > the nitrogenous compounds, in both resistant and susceptible strains. On the other hand, caffeine (lethal effect increased about twice), barbital (about twice), isobarbituric acid (less than twice) and bromacil (up to eight times) synergised malathion in malathion-resistant strains and antagonised in the susceptible strains. Total in-vivo esterases, carbox-ylesterases and cytochrome P₄₅₀ of susceptible and resistant strains showed significantly increased activity or content when treated with either insecticide plus a heterocyclic compound. Exceptions were with bromacil and malathion and for the malathion-specific strain, Kano-C with malathion and the N-heterocycles.     

Diazinon poisoning in large white butterfly larvae and the influence of sesamex and piperonyl butoxide

The toxicity of diazinon and diazoxon to fourth instar Pieris brassicae larvae was determined, with or without modifying chemicals. Piperonyl butoxide and sesamex antagonised diazinon but synergised diazoxon. The penetration, excretion and internal concentration of diazinon were measured following topical application. Penetration of diazinon followed first order kinetics and was considerably slower after pretreatment with sesamex and piperonyl butoxide. Pretreatment with piperonyl butoxide increased the internal concentration of diazinon, but the onset of symptoms of poisoning was delayed, presumably because of inhibition of diazinon activation.     

Resistance to cyfluthrin and tetrachlorvinphos in the lesser mealworm, Alphitobius diaperinus, collected from the eastern United States

The lesser mealworm, Alphitobius diaperinus (Panzer), is an important pest in poultry facilities. The toxicity of cyfluthrin and tetrachlorvinphos to five strains of the lesser mealworm was compared with the toxicity to a susceptible laboratory strain. Bioassays were carried out with both larvae and adults. For the susceptible strain, cyfluthrin and tetrachlorvinphos had similar toxicity to adults, but cyfluthrin was 5 times more toxic to larvae when compared with tetrachlorvinphos. High levels of resistance to tetrachlorvinphos in two beetle strains were detected in both larvae and adults, although these strains were heterogeneous and still contained susceptible individuals. Resistance to cyfluthrin ranged from 1.7- to 9.5-fold for adults and from 0.5- to 29-fold for larvae at the LC(95). Overall, the patterns of resistance did not mirror the insecticide use patterns reported at these facilities. The implications of these results to management of the lesser mealworms are discussed.     

Multiple Resistance in the Larger House Fly Musca domestica in Germany

Populations of the housefly Musca domestica isolated from farms in different German districts with strong resistance problems were compared to laboratory strains with varying resistance spectra. Resistance against pyrethroids, organophosphates and carbamates was tested using impregnated filter papers, and by topical application using a susceptible housefly strain (origin WHO) for comparison. The multi-resistant fly strains tested had a strong resistance against these insecticide groups, ranging from 37- to >10000-fold for organophosphates and 150- to >6600-fold for pyrethroids. The constituent enantiomer pairs of the α-cyano-pyrethroid cyfluthrin were tested, as was beta-cyfluthrin. With respect to multi-resistant fly strains, the isomers II and IV had the best activity, with LD₅₀ values of 0·012 and 0·014 μg per fly, respectively. In addition, different groups of insect growth regulators (juvenile hormone analogues, chitin synthesis inhibitors and one triazine derivative) were tested in a special larvicidal test. The chitin synthesis inhibitors were quite effective against multi-resistant M. domestica strains except for one strain with strong resistance against chitin synthesis inhibitors, developed after extensive treatments with benzoylphenylureas for several years. The fly strains tested were not resistant against cyromazine. Additionally, the insecticides were combined with the synergists piperonyl butoxide, tributylphosphorotrithioate (DEF) and Cibacron blue and tested against the fly strain with the strongest resistance spectrum (‘Grimm’) in comparison to the susceptible strain (‘WHO-N’). Piperonyl butoxide had the greatest effect on the efficacy of cyfluthrin followed by Cibacron blue and DEF. In a parallel investigation with susceptible and resistant house fly strains, different enzyme activities related with resistance mechanisms were tested, e.g. glutathione S-transferase (3·5-fold) and mixed-function oxidase (2·3-fold). Implications of these results for management of insecticide resistance in M. domestica are discussed.     

Effects of organic‐farming‐compatible insecticides on four aphid natural enemy species

BACKGROUND: The toxicities of pyrethrins + rapeseed oil, pyrethrins + piperonyl butoxide (PBO), potassium salts of fatty acids and linseed oil were assessed in the laboratory on the parasitic wasp Aphidius rhopalosiphi (Destefani‐Perez), the ladybird Adalia bipunctata (L.), the rove beetle Aleochara bilineata (Gyll.) and the carabid beetle Bembidion lampros (Herbst.). The methods selected were residual contact toxicity tests on inert and natural substrates. RESULTS: Both the pyrethrin products led to 100% mortality in the adult parasitic wasps and ladybird larvae on glass plates and plants. The pyrethrins + PBO formulation was toxic for B. lampros on sand and natural soil, but the pyrethrins + rapeseed oil formulation was harmless for this species. Insecticidal soaps were harmless for all these beneficial species. None of the tested products significantly affected the parasitism of the onion fly pupae by A. bilineata. CONCLUSION: The results indicated the potentially high toxicity of natural pyrethrins for beneficial arthropods. Although this toxicity needs to be confirmed in field conditions, the toxicity levels obtained in the laboratory were similar to or higher than those of several synthetic insecticides known to be toxic in the field. Insecticidal soaps could be considered as an alternative for aphid control in organic farming in terms of selectivity. Copyright © 2010 Society of Chemical Industry     

Larvicidal activity of Cnidium monnieri fruit coumarins and structurally related compounds against insecticide-susceptible and insecticide-resistant Culex pipiens pallens and Aedes aegypti

BACKGROUND: An assessment was made of the toxicity of imperatorin and osthole identified in Cnidium monnieri fruit, 11 related compounds and five insecticides to larvae from insecticide‐susceptible Culex pipiens pallens (KS‐CP strain) and Aedes aegypti and wild C.p. pallens (YS‐CP colony) using a direct‐contact mortality bioassay. Results were compared with those of the conventional larvicide temephos. RESULTS: Imperatorin (LC₅₀ = 3.14 and 2.88 mg L^?1) was 1.9‐, 3.7‐ and 4.2‐fold and 2.4‐, 4.5‐ and 4.6‐fold more toxic than isopimpinellin, isoimperatorin and osthole against susceptible C. p. pallens and A. aegypti larvae respectively. Overall, all of the compounds were less toxic than temephos (0.011 and 0.019 mg L^?1). The toxicity of these compounds was virtually identical against larvae from the two Culex strains, even though YS‐CP larvae were resistant to fenthion (resistance ratio RR = 390), deltamethrin (RR = 164), cyfluthrin (RR = 14) and temephos (RR = 14). This finding indicates that the coumarins and the insecticides do not share a common mode of action. The structure–activity relationship indicates that the chemical structure and alkoxy substitution and length of the alkoxyl side chain at the C8 position are essential for imparting toxicity. CONCLUSION: The C. monnieri fruit‐derived coumarins and the related coumarins described merit further study as potential insecticides or lead molecules for the control of insecticide‐resistant mosquito populations. Copyright © 2012 Society of Chemical Industry     

Synergism of teflubenzuron and chlorfluazuron in an acylurea-resistant field strain of Plutella xylostella L. (lepidoptera: Yponomeutidae)

Topical application of the synergists piperonyl butoxide (PB) and S,S,S-tributyl phosphorotrithioate (DEF) to second-instar larvae of a standard laboratory strain (FS) and an unselected Malaysian field strain (CH) of the diamondback moth Plutella xylostella had no significant effect on the toxicity of the acylurea insecticides, chlorfluazuron and teflubenzuron, in a subsequent leafdip bioassay. In contrast, pre-treatment with PB or DEF in acylurea-selected subpopulations of the CH strain with varying levels of cross-resistance to chlorfluazuron and teflubenzuron significantly increased (up to 34-fold and 28-fold, respectively) the toxicity of both compounds, suggesting that microsomal monooxygenases and esterases may be involved in resistance. The addition of a mineral oil, ‘Sunspray 6E’, to topically-applied chlorfluazuron consistently reduced its LD₅₀ value, and the effect of the oil appeared to be greatest on the most resistant population of P. xylostella. However, the effects of the oil were not significant (P > 0·05) and further studies are necessary to determine whether a penetration factor is present in the CH strain.     

Persistence and activity of mexacarbate and its metabolites against spruce budworm larvae

This study was conducted to determine if metabolites of mexacarbate contribute to its residual toxicity to spruce budworm (Choristoneura fumiferana) larvae. Potted white spruce (Picea glauca) trees were treated with ‘Zectran’ UCZF # 19 at 100 g a.i. ha^?1 and kept in a glasshouse. Mexacarbate residues declined by 98–99% within three days and reached non-detectable levels 10 days after treatment. Mortality of larvae fed on buds from these trees declined more gradually and was still 19–27% when exposed 10 days after treatment. The very low levels of mexacarbate (<0.07 μg g^?1) found after three days did not produce such mortality. Gas chromatographic analysis of metabolites in needles revealed that after three days, 4-methylformamido-3,5-xylyl N-methylcarbamate was present at levels 20–30 times higher than the parent compound. This metabolite was about 50 times less toxic than mexacarbate to larvae when applied topically but was only 7 times less toxic when ingested. Two other methylcarbamate metabolites, the amino, and methylamino analogues were detectable for one day following treatment but not at later time points. They were as toxic as mexacarbate both topically and orally. Based on these findings, the methylformamido analogue could contribute to the residual toxicity of mexacarbate treatments of spruce.     

Effects of piperonyl butoxide and DEF on the metabolism of methoprene by the imported fire ant,Solenopsis invicta Buren

Studies are presented on the effects of two synergists, piperonyl butoxide and S,S,S-tributyl phosphorotrithioate, on the metabolism of methoprene [isopropyl (2E,4E)-11-methoxy-3,7,11-trimethyldodeca-2,4-dienoate], an insect growth regulator, by the castes of the imported fire ant, Solenopsis invicta Buren. In adults, but not in larvae, pharate pupae, and pupae, piperonyl butoxide, a microsomal enzyme inhibitor, reduced methoprene metabolism by blocking O-demethylation. S,S,S-Tributyl phosphorotrithioate, an esterase and microsomal oxidase inhibitor, was most effective in reducing methoprene metabolism in larvae. In toxicity studies, against pharate pupae, the O-demethylated methoprene metabolite (alcohol-ester) was shown to be more toxic than methoprene. Synergists may be useful in bait formulations used for imported fire ant control to extend the effectiveness of methoprene.     

Examination of stability of resistance and cross-resistance patterns to acylurea insect growth regulators in field populations of the diamondback moth,Plutella xylostella,from Malaysia

In teflubenzuron and teflubenzuron/chlorfluazuron laboratory-selected sub-populations of a Cameron Highlands (1988) strain of Plutella xylostella L., resistance to teflubenzuron reached much greater levels than chlorfluazuron but declined at a correspondingly greater rate to give similar resistance levels after 10–13 generations. There was little evidence of cross-resistance to flufenoxuron and none to hexaflumuron in these populations. Reselection of a Cameron Highlands population with teflubenzuron after 22 generations resulted in a significant (P < 0.05) increase in resistance after three generations. In two more recently collected strains from lowland Malaysia, Sawi (1991) and Serdang (1992) high levels of resistance to teflubenzuron were found, but only the former showed any apparent resistance to chlorfluazuron. There was also evidence of resistance to diflubenzuron in the Sawi strain (Serdang not examined). Resistance to teflubenzuron appeared to be unstable in unselected sub-populations of both lowland strains. Selection of the Sawi strain with teflubenzuron did not effect cross-resistance to chlorfluazuron, while attempted selection with chlorfluazuron had no effect on resistance to either compound. Selection of the Sawi strain with diflubenzuron increased resistance to teflubenzuron but had no effect on resistance to chlorfluazuron. In contrast to the Sawi strain, selection of the Serdang strain with teflubenzuron resulted in cross-resistance to chlorfluazuron. Synergist experiments with piperonyl butoxide (PB) and S,S,S-tributyl phosphorotrithioate (DEF) suggested that resistance to teflubenzuron in the lowland strains may involve both microsomal monooxygenases and esterases. The ovicidal activity of teflubenzuron, chlorfluazuron, hexaflumuron and flufenoxuron was consistently less than their activity against second-instar larvae, hexaflumuron, followed by teflubenzuron, showing the greatest relative ovicidal activity. Hexaflumuron was markedly more active than teflubenzuron against eggs from acylurea-selected Cameron Highlands populations and there was some evidence that resistance to teflubenzuron may be expressed at a lower level in eggs than in larvae in one such strain.     

The pattern of cross-resistance to insecticides and juvenile hormone analogues in a diflubenzuron-resistant strain of the cotton leaf worm Spodoptera littoralis boisd

The rate of development of resistance to diflubenzuron in a laboratory susceptible strain of the cotton leafworm Spodoptera littoralis Boisd., the pattern of cross-resistance exhibited by the resistant strain to several insecticides and juvenile hormone analogues, as well as the synergistic action of piperonyl butoxide (PB) and S, S, S-tributyl phosphorotrithioate (TBP) with insecticides or diflubenzuron on both strains, were investigated. Resistance to diflubenzuron increased slightly in the first eight selected generations and was enhanced by further selection until in generation 30, the selected strain attained the high level of resistance of 290.7-fold, compared with the parent strain. The resistant strain when challenged with either insecticides or juvenile hormone analogues at selected generations (5, 10, 15, 20, 25 and 30) exhibited different levels of resistance to several insecticides representing organochlorine and organo-phosphorus compounds, carbamates and pyrethroids, but a clear case of negative correlation was indicated between resistance to diflubenzuron and juvenile hormone analogues. With regard to the synergistic action of PB and TBP on the toxicity of either diflubenzuron or insecticides against the fourth-instar larvae of the susceptible strain, methomyl showed slight levels of synergism when it was combined with them. With the exception of cypermethrin, which was not affected by the two synergists, lower levels of synergism were observed with the compounds endrin, diflubenzuron and fenvalerate when they were combined with the same synergists. These two synergists however, antagonised the toxic action of the organophosphorus compounds phosfolan and chlorpyrifos. Against the resistant strain, endrin was moderately synergised by TBP but only slightly by PB. Slight levels of synergism were observed when methomyl, phosfolan and diflubenzuron were combined with either synergist, but both antagonised chlorpyrifos and fenvalerate. Resistance to diflubenzuron and to the other tested chemicals in the resistant strain was scarcely affected by the two synergists.     

Synthetic pyrethroids: Toxicity and synergism on dietary exposure of Tribolium castaneum (Herbst) larvae

The potency of six dietary pyrethroids, as toxicants and inhibitors of weight gain in first- and fourth-instar Tribolium castaneum (Herbst) larvae, decreased in the order of cis-cypermethrin and deltamethrin > trans-cypermethrin and cis-permethrin > fenvalerate and trans-permethrin. Dosages that reduced larval weight also delayed pupation and emergence, probably due to their antifeeding activity. Three oxidase inhibitors (piperonyl butoxide, O, O-diethyl O-phenyl phosphorothioate, and O-isobutyl O-prop-2-ynyl phenylphosphonate), at a dietary concentration of 100 mg kg^?1, had little or no effect on the toxicity of trans-permethrin, but strongly synergised the toxicity of cis-cypermethrin by about 3-, 3- and 10-fold, respectively. Piperonyl butoxide also synergised the toxicity of cis-permethrin, trans-cypermethrin and deltamethrin, but not that of fenvalerate. On the other hand, an esterase inhibitor, profenofos, did not enhance the potency of any of the α-cyano-3-phenoxybenzyl pyrethroids. Oxidases appear to be more important than esterases in pyrethroid detoxification by T. castaneum larvae.     

氟铃脲对韭菜迟眼蕈蚊不同虫态的致毒特点及毒力

为明确氟铃脲对韭菜迟眼蕈蚊不同虫态的致毒特点及毒力,采用胃毒触杀联合毒力法、药液定量滴加法及药膜法分别对韭菜迟眼蕈蚊卵、幼虫、蛹、成虫进行了生物测定。结果表明,经氟铃脲处理的0.5~1、1.5~2和2.5~3日龄韭菜迟眼蕈蚊卵至孵化24 h后,LC_(50)依次为2.27、1.60和0.64 mg/L,对1.5~3日龄卵的毒力高于对0.5~1日龄卵;经氟铃脲处理的2日龄卵、2龄幼虫、4龄幼虫、1日龄和3日龄蛹至羽化时LC_(50)分别为0.06、0.30、0.34、24.05和27.42 mg/L,毒力程度随韭菜迟眼蕈蚊发育而逐步下降;对蛹和成虫毒力较低,100 mg/L氟铃脲染毒1、3日龄蛹的羽化率分别高于10%和20%;药膜法100、1 000 mg/L氟铃脲处理成虫24 h,校正死亡率低于20%。研究表明,氟铃脲对韭菜迟眼蕈蚊各虫态的生长发育均有不利影响,抑制卵的孵化并导致初孵幼虫存活率降低;对幼虫毒杀作用较慢,对蛹及成虫阶段毒力较低。