Pyrethroid resistance and cross‐resistance in the German cockroach,Blattella germanica (L)

A German cockroach (Blatella germanica (L)) strain, Apyr‐R, was collected from Opelika, Alabama after control failures with pyrethroid insecticides. Levels of resistance to permethrin and deltamethrin in Apyr‐R (97‐ and 480‐fold, respectively, compared with a susceptible strain, ACY) were partially or mostly suppressed by piperonyl butoxide (PBO) and S,S,S,‐tributylphosphorotrithioate (DEF), suggesting that P450 monooxygenases and hydrolases are involved in resistance to these two pyrethroids in Apyr‐R. However, incomplete suppression of pyrethroid resistance with PBO and DEF implies that one or more additional mechanisms are involved in resistance. Injection, compared with topical application, resulted in 43‐ and 48‐fold increases in toxicity of permethrin in ACY and Apyr‐R, respectively. Similarly, injection increased the toxicity of deltamethrin 27‐fold in ACY and 28‐fold in Apyr‐R. These data indicate that cuticular penetration is one of the obstacles for the effectiveness of pyrethroids against German cockroaches. However, injection did not change the levels of resistance to either permethrin or deltamethrin, suggesting that a decrease in the rate of cuticular penetration may not play an important role in pyrethroid resistance in Apyr‐R. Apyr‐R showed cross‐resistance to imidacloprid, with a resistance ratio of 10. PBO treatment resulted in no significant change in the toxicity of imidacloprid, implying that P450 monooxygenase‐mediated detoxication is not the mechanism responsible for cross‐resistance. Apyr‐R showed no cross‐resistance to spinosad, although spinosad had relatively low toxicity to German cockroaches compared with other insecticides tested in this study. This result further confirmed that the mode of action of spinosad to insects is unique. Fipronil, a relatively new insecticide, was highly toxic to German cockroaches, and the multi‐resistance mechanisms in Apyr‐R did not confer significant cross‐resistance to this compound. Thus, we propose that fipronil could be a valuable tool in integrated resistance management of German cockroaches. © 2001 Society of Chemical Industry     

Brief exposure of Blattella germanica (Blattodea) to insecticides formulated in various microcapsule sizes and applied on porous and non-porous surfaces

BACKGROUND: The authors explored how microcapsule size and brief exposure affected the bioavailability of five microencapsulated insecticide formulations, chlorpyrifos 23.1 g L(-1) CS (Detmol-PRO), chlorpyrifos 20 g L(-1) CS (Empire 20), fenitrothion 20 g L(-1) CS (Detmol-Mic), cyphenothrin 10 g L(-1) CS (Detmol-CAP) and diazinon 30 g L(-1) CS (Diacap), to Blattella germanica L. on porous and non-porous surfaces. The hypothesis was tested that microencapsulated (CS) insecticides comprising larger microcapsules show higher efficacy on porous surfaces than formulations with smaller microcapsules. RESULTS: Brief exposure was accomplished by allowing B. germanica to cross a 0.3 m insecticide barrier in 30 s (1.01 cm s(-1)). Such short exposure did not lead to 100% mortality in any formulation or surface tested. Significant differences in bioavailability on the porous and the non-porous surfaces were found: the largest difference was observed in Empire 20 and Detmol CAP, while bioavailability of Detmol MIC did not differ on porous and non-porous surfaces. Comparison of their microcapsule size spectra revealed that formulations containing larger microcapsules had higher efficacy on porous surfaces than formulations with smaller microcapsules. In order to explain the difference in efficacy, the variance of microcapsule sizes was regressed on the efficacy ratio on porous versus non-porous surfaces. Although negative correlation was evident between size of capsules and the efficacy ratio on porous and non-porous surfaces, the difference in the slope parameter was not statistically significant. CONCLUSION: Brief contact of B. germanica with insecticide spray residues, which is common in barrier treatment, may lead to low efficacy, especially on porous surfaces. The latter should be preferably treated with CS insecticides containing a fraction with large capsules. In addition to the size of the microcapsules, the role of other factors, such as wall capsule thickness and chemical composition, on CS insecticide activity on various surfaces should be examined in future work.     

Correlation of a resistance-associated Rdl mutation in the German cockroach, Blattella germanica (L), with persistent dieldrin resistance in two Danish field populations

Danish Blattella germanica (L) populations carry the resistance-associated mutation A302S within the Resistance to dieldrin (Rdl) gene. The mutation has remained in field populations long after the discontinuation of dieldrin for cockroach control. The mutation has also persisted in our laboratory strains with high and intermediate frequencies for more than 8 years without selection. The toxicity of dieldrin was tested by topical application to male cockroaches in the susceptible strain DPIL-SUS and two field strains, Zo960302 and Su960304, which were 1270- and 15-fold resistant to dieldrin at LD50. We report the sequencing of exon 7 of the B. germanica Rdl gene and the finding of the putative resistance-associated A302S mutation. We have developed and implemented a PCR-based diagnostic method with the detection of a restriction endonuclease polymorphism, which allows for easy discrimination of susceptible, resistant and heterozygote genotypes. The frequency of the resistance-associate allele A302S was 0.97 and 0.38 in the Zo960302 and Su960304 populations, respectively. The cockroach Rdl A302S allele confers high dieldrin resistance in homozygotes and intermediate resistance in heterozygotes, and its presence is responsible for the persisting dieldrin resistance in Danish populations of B. germanica.     

Efficacy of noviflumuron gel bait for control of the German cockroach, Blattella germanica (Dictyoptera: Blattellidae)-laboratory studies

The insecticidal activity of a cockroach gel bait containing a chitin synthesis inhibitor, noviflumuron, was evaluated using laboratory and field strains of the German cockroach, Blattella germanica (L.). Noviflumuron gel bait (0.01-5 mg g(-1)) caused > or = 90% nymphal mortality to laboratory and field strains of B. germanica in choice tests after 11 and 19 days of continuous exposure respectively. In 1 m x 1 m bioassay arenas, laboratory strain B. germanica population levels exposed to 5 mg g(-1) noviflumuron bait or 0.1 mg g(-1) fipronil gel bait were significantly lower than untreated population levels after 3 weeks and 1 week of exposure respectively. Various noviflumuron bait exposure periods (2, 4 and 7 weeks) caused similar population reductions, with a mean of 99.3 (+/- 0.3)% at 7 weeks. Fipronil gel bait caused 100% population reduction at 2 weeks post-exposure. The control population increased 89.0% at 7 weeks. In a simulated kitchen experiment with mixed stage laboratory populations, cockroach trap catches decreased 96.8 (+/- 2.0)% at 8 weeks in the 0.5 mg g(-1) noviflumuron bait treatment. The trap catches in the control increased 506.5 (+/- 493.7)% during the same period. Trap catch reduction by 0.1 mg g(-1) fipronil gel bait reached 100% at 4 weeks. Noviflumuron bait caused significantly lower nymph/total ratios to B. germanica populations in bioassay arenas from 2 weeks after exposure, demonstrating its effectiveness as a control agent for B. germanica with a pattern of activity similar to that expected from a chitin synthesis inhibitor.     

Sublethal effects of insecticides on the diamondback moth Plutella xylostella (L.)

The effect of sublethal concentrations (LC₁ and LC₅₀) of permethrin, fenvalerate, methamidophos and carbaryl on diamondback moth development, female fecundity and insect behaviour was investigated. All the insecticides had deleterious effects on the number of larvae surviving to pupae, the duration of the pupal period, the number of pupae surviving to adulthood, and cocoon formation in pupae. Prolonged duration of the larval period, from third instar to pupation, and deformed pupae were also observed. Permethrin, fenvalerate and carbaryl caused latent toxicity and deformed wings in the adults. Pyrethroids and methamidophos reduced the longevity of the adults whereas carbaryl increased it. Except for permethrin, the insecticides inhibited female fecundity. At LC₁ and LC₅₀ concentrations, the pyrethroids showed both repellent and antifeedant activity against larvae, and female moths preferred to oviposit on untreated leaf discs rather than on those treated with the pyrethroids at concentrations equal to their LC₅₀ values.     

Cross-Resistance to Imidacloprid in Strains of German Cockroach (Blattella germanica) and House Fly (Musca domestica)

The toxicity of a promising new insecticide, imidacloprid, was evaluated against several susceptible and resistant strains of German cockroach and house fly. Imidacloprid rapidly immobilized German cockroaches followed by a period of about 72 h during which some cockroaches recovered. After 72 h there was no further recovery. Imidacloprid-treated houseflies were immobilized more slowly than treated cockroaches, with the maximum effect observed after 72 h, and there was no recovery. Based upon 72-h LD₅₀ values imidacloprid was moderately toxic to German cockroaches (LD₅₀ values were 6–8 ng mg^-1) and had only low toxicity to house flies (LD₅₀ 140 ng mg^-1). Piperonyl butoxide (PBO) blocked the observed recovery in German cockroaches. PBO also greatly enhanced the 72-h LD₅₀ of imidacloprid from 43- to 59-fold in cockroaches and 86-fold in house flies. Two strains of German cockroach (Baygon-R and Pyr-R) showed >4-fold cross-resistance to imidacloprid. This cross-resistance could not be suppressed by PBO, suggesting that P450 monooxygenase-mediated detoxication is not responsible for this cross-resistance. Variation in the level of synergism observed with PBO (between strains) suggests the ‘basal’ level of monooxygenase-mediated detoxication of imidacloprid is quite variable between strains of German cockroach. The AVER and LPR strains of house fly showed significant cross-resistance to imidacloprid. PBO reduced the level of cross-resistance in AVER from >4·2-fold to 0·5-fold (i.e. the AVER strain LD₅₀ was half that of the susceptible strain when both were treated with PBO), but PBO did not suppress the cross-resistance in LPR. These data suggest monooxygenases are the mechanism responsible for cross-resistance to imidacloprid in AVER, but not in the LPR strain. © of SCI.     

Reduced egg viability in codling moth Cydia pomonella (L.) (Lepidoptera: Tortricidae) following adult exposure to novaluron

BACKGROUND: The codling moth, Cydia pomonella (L.), is one of the principal pests of pome fruits in the world. The effects of novaluron, a benzoylurea chitin synthesis inhibitor insecticide registered for use on apples in the USA, on fecundity and egg viability in codling moth were studied under laboratory conditions. Three different exposure methods were investigated: ingestion, contact and topical spray. Additionally, the duration of novaluron sublethal effects was measured subsequent to the three modes of exposure. RESULTS: The fecundity of codling moth adults was not significantly affected by novaluron with any of the exposure methods. However, novaluron did cause significant reductions in the proportion of egg hatch with all three exposure methods. The duration of sublethal effects was 9 days or more for all modes of exposure, but with the topical spray these effects began to diminish after 6 days. CONCLUSION: Novaluron does not affect fecundity in codling moth, but has significant sublethal activity by reducing egg viability subsequent to adult exposure. The topical, contact and ingestion exposures all induce sublethal effects after exposure, and these persist to various degrees throughout codling moth oviposition. A more complete understanding of novaluron's lethal and sublethal activities will help IPM practitioners optimize its use for management of the codling moth. Copyright © 2008 Society of Chemical Industry     

响应面优化烟草提取物微囊制备工艺

烟草提取物具有良好的杀虫活性。为提高其稳定性,以烟草提取物为芯材,以明胶、阿拉伯胶为壁材,采用复凝聚法制备了烟草提取物微囊。以包埋率为评价指标,采用响应面法对微囊制备工艺进行优化。对微囊进行了表面形态观察、粒径测定、红外光谱分析、热稳定性分析及室内毒力测定。结果表明:当乳化剂质量分数4%、明胶质量分数2.05%、阿拉伯胶质量分数3%、壁芯质量比1.34 : 1.00以及复凝聚反应时间为36 min时,制备的微囊包埋率最高,理论包埋率为58.93%。经验证,在此条件下实际包埋率为58.42% ± 0.12%,接近理论值。所得微囊表面光滑,成囊性好,粒径分布在4.72~17.05 μm之间,中位径8.63 μm;在877.55和2 922.13 cm?1处保留了烟草提取物的红外特征峰;微囊化能够提高烟草提取物的热稳定性;室内毒力测定结果表明,烟草提取物微囊的LC₅₀值为20.19 mg/mL,与烟草提取物的毒力水平相当,说明微囊化没有降低烟草提取物的毒力。本研究可以为烟草提取物微囊制备提供参考。     

Response of susceptible and resistant peach-potato aphids Myzus persicae (Sulz.) to insecticides in leaf-dip bioassays

The response of susceptible (S), moderately resistant (R₁) and strongly resistant (R₂) peach-potato aphids, Myzus persicae (Sulz.) to organophosphorus, carbamate and pyrethroid insecticides was tested by a leaf-dip bioassay. The aphids were placed on potato leaves (dipped in insecticide solutions 1–2 or 24 h before infestation) and their mortality examined 48 h later. R₁ aphids were virtually susceptible to most of the carbamates, demephion and acephate, but were slightly to moderately resistant (2.1–9.4 times) to permethrin, cypermethrin and (S)-α-cyano-3-phenoxybenzyl (1R)-cis-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropanecarboxylate (I), (NRDC 161), to 5,6,7,8-tetrahydro-2-methylquinolin-4-yl dimethylcarbamate (II), (Hoechst 25 682) and demeton-S-methyl. R₂ aphids resisted more strongly or very strongly (between 65 and 1280 times) the pyrethroids, demeton-S-methyl (×94), II (×83) and demephion (×9), and were slightly to moderately (2–5 times) resistant to acephate, pirimicarb, ethiofencarb and 2-(dimethylcarbamoyloxyimino)-3-methoxyimino-N,N- dimethylbutyramide (III), (DPX 3853). Both resistant strains were susceptible to nitrilacarb [4,4-dimethyl-5-(methylcarbamoyloxyimino)pentanenitrile] complex (1:1) with zinc chloride (IV), (AC 85 258). The implications of these results in terms of practical aphid control are discussed.     

Factors affecting the sequential acquisition by Danish houseflies (musca domestica L.) of resistance to organophosphorus insecticides

The prolonged use of dimethoate, introduced into Denmark to control houseflies (Musca domestica L.) that had become resistant to parathion and diazinon, resulted ultimately in dimethoate resistance. Selection with dimethoate led to the disappearance of the hydrolytic phosphatase, a major mechanism of resistance to parathion and diazinon, and its replacement by the acetylcholinesterase AChER with somewhat decreased sensitivity to inhibition by organophosphorus (OP) insecticides. The hydrolytic phosphatase probably disappeared because low substrate turn-over made it ineffective against dimethoxon (O, O-dimethyl S-methylcarbamoylmethyl phosphorothioate, also known as omethoate). which accumulates at higher concentrations than paraoxon (diethyl4-nitrophenyl phosphate) in the haemolymph. Dimethoate selected AChER preferentially because it improved the chances of houseflies surviving against the relatively poor AChE inhibitor dimethoxon, whereas its relatively small insensitivity to OP insecticides, unimportant against good inhibitors such as paraoxon, prevented its selection by parathion.     

几种杀虫剂防治花椰菜小菜蛾试验初报

5％锐劲特悬浮剂1400倍、10％除尽悬浮剂1400倍、20％美满悬浮剂2000倍、4．5％高效氯氰菊脂乳油2000倍、2．5％溴氰菊脂乳油2000倍、5％抑太保乳油1400倍等杀虫剂对花椰菜小菜蛾具有较好的防治效果，且持效期长，对蔬菜安全；药后3d防效在84．80％～92．96％；药后7d防效在87．92％～95．61％；药后10d防效在87．22％～93．77％。     

Penetration of insecticides through the foregut of the honeybee (Apis mellifera L.)

The rates of penetration of ¹⁴C-labeled insecticides (parathion, carbaryl, and dieldrin) through the foregut of the honeybee (Apis mellifera L.) were measured in vitro and in vivo. Uptake of the insecticides from the lumen of the foregut into foregut tissue was directly proportional to insecticide lipophilicity, but penetration through the foregut was not. Of the three insecticides studied, parathion appeared to possess the optimal physicochemical characteristics required for penetration. The uptake of carbaryl and release of dieldrin by the foregut tissues may limit their respective penetration rates. Insecticide penetration was found to be inversely proportional to the sucrose concentration in the lumen of the foregut in both in vitro and in vivo studies. The oral toxicity of carbaryl showed a similar dependence on the sucrose concentration of the solution in which the insecticide was fed. The data presented indicate that the honeybee foregut is permeable to lipophilic compounds and strongly suggest that this permeability may contribute substantially to the toxicity of orally ingested insecticides in this insect.     

嗜线虫致病杆菌与七种杀虫剂混配对小菜蛾毒杀增效作用评价

采用浸叶法测定了嗜线虫致病杆菌Xenorhabdus nematophila HB310(Xn HB310)与7种常用杀虫剂混配后对小菜蛾3龄幼虫的毒杀增效作用,并对具有增效作用的混配组合进行了最佳配比的筛选和增效作用的评价。结果显示,Xn HB310仅与氯氰菊酯混配表现出明显的增效作用,协同毒力指数(cf)为30.9;当Xn HB310与氯氰菊酯质量比在1006.4∶2.6～816∶4之间时,混配药剂均表现为增效作用;当两种药剂的质量比为952∶3时,增效作用最强,此时的共毒系数最高为335。Xn HB310与乐斯本、吡虫啉或甲氨基阿维菌素苯甲酸盐(甲维盐)混配均表现为相加作用,cf值分别为9.6、-6.9和-18.6,Xn HB310与菜喜、灭幼脲或阿维菌素混配则表现出明显的拮抗作用,cf值分别为-48.4、-24.9和-57.1。     

Diurnal fluctuations in susceptibility to insecticides in several strains of the yellow fever mosquito (Aedes aegypti L.)

Larvae and adults of three strains of the yellow fever mosquito Aedes aegypti L. were tested to determine the presence or absence of a diurnal rhythm of susceptibility to the organochlorine insecticides dieldrin and DDT. Each strain showed different patterns of larval susceptibility to the toxicants. Larvae and adults of the same strains produced opposite time-dependent responses to treatment. The significance of daily patterns of changing susceptibility in toxicological studies is discussed.     

Pharmacological evidence for a discrete neurotoxic action of dieldrin (HEOD) in the American cockroach,Periplaneta americana (L.)

The excitatory effects of HEOD poisoning on spontaneous activity, and synaptic function in the sixth abdominal ganglion of the American cockroach are described. These effects are shown to be antagonized by Mg²⁺, hemicholinium-3, atropine, and d-turbocurarine. HEOD poisoning did not alter the nicotine sensitivity of the ganglion. On the basis of the findings it is hypothesized that HEOD acts at presynaptic membranes of cholinergic junctions, causing excessive and spontaneous release of presynaptic stores of acetylcholine.     

Binding of insecticides to macromolecules in the blood of the rat and American cockroach

This investigation concerns transport of DDT, dieldrin and parathion in the blood of the rat and roach. Using gel filtration, ion-exchange chromatography, and disc gel electrophoresis, a method for the isolation of some of the plasma proteins that bind DDT and dieldrin has been demonstrated. By a variety of staining procedures, these macromolecules were shown to be of a lipoprotein nature. A tentative molecular weight of 520,000 was obtained for one of the binding proteins in roach hemolymph.