Knockdown resistance to dichlorodiphenyl-trichloroethane and pyrethroid insecticides in the napts mutant of Drosophila melanogaster is correlated with reduced neuronal sensitivity

Resistance to pyrethroid insecticides and dichlorodiphenyltrichloroethane (DDT) was investigated in the nap^ts (no action potential, temperature sensitive) mutant of Drosophila melanogaster. In surface contact bioassays, the nap^ts strain showed threefold resistance to deltamethrin at the LC₅₀ level when compared to susceptible Canton-S flies. Cross-resistance was also observed to DDT and the pyrethroids NRDC 157 [3-phenoxybenzyl [1R,cis]-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropanecarboxylate], fenfluthrin, and MTI-800 [1-(3-phenoxy-4-fluorophenyl)-4-(4-ethoxyphenyl)-4-methylpentane]. The onset of intoxication by pyrethroids in nap^ts flies was markedly delayed, a finding that is consistent with the existence of a resistance mechanism involving reduced neuronal sensitivity. Resistance at the level of the nerve was confirmed by electrophysiological recordings of spontaneous and evoked activity in the dorsolongitudinal flight muscles of poisoned flies. Preparations from nap^ts insects treated with fenfluthrin displayed longer latencies to the appearance of spontaneous activity and also an absence or reduction in burst discharges compared to equivalent preparations from susceptible individuals. These results are discussed in light of competing hypotheses concerning the mechanism underlying knockdown resistance and reduced nerve sensitivity in insects.     

Impact of deltamethrin aerial sprays on adult Cyrtobagous salviniae in Botswana

The risk and effect of the insecticide deltamethrin, applied aerially in Botswana to control and eradicate tsetse fly, was studied on the non-target weevil Cyrtobagous salviniae, a biocontrol agent of the aquatic weed Salvinia molesta. Environmentally-simulated short-term toxicity bioassay used open iron cages and closed plastic basins containing weevils and salvinia placed in riverine water bodies, where they were exposed to the aerial applications of deltamethrin over the Kwando–Linyanti system in 2006. Control samples were placed 40 km outside the sprayed area. Weevil mortality, determined at 12, 36 and 60 hours after the aerial application, reached a maximum of 27%. No significant difference in mortalities was observed between the closed basins and the open cages. The amount of deltamethrin deposited at ground level was between 1.2 and 6.4 μg m^?2  and the insecticide toxicity was related to the weevil mortality. Simultaneous field monitoring through five spray applications showed that weevil abundance declined in late winter. Deltamethrin had a negligible impact on the weevil's ability to control salvinia under field conditions, probably due to the weevils’ protective mechanism and because vegetation could act as a barrier, preventing the insecticide from reaching the weevils. Minimum impacts of deltamethrin on the weevils in the present study and their recovery in the field are consistent with those of earlier spray applications in the Okavango Delta, Botswana.     

溴氰菊酯对飞蝗羧酸酯酶基因表达的影响

【目的】研究溴氰菊酯作用下飞蝗羧酸酯酶基因的mRNA表达特性,为溴氰菊酯的代谢解毒及飞蝗Locusta migratoria防治中抗性风险的评估提供基础资料。【方法】本文采用不同剂量溴氰菊酯处理3龄飞蝗,提取总RNA,体外反转录合成cDNA模板,采用Real-time PCR技术分析飞蝗羧酸酯酶基因在溴氰菊酯不同浓度和不同时间处理后的表达模式。【结果】飞蝗经不同浓度溴氰菊酯处理12 h后,LmCesA3和LmCesE1表现为诱导效应;除LmCesA2外,其余羧酸酯酶基因经溴氰菊酯LD30剂量处理后分别在不同的时间点表现为诱导效应。【结论】5个羧酸酯酶基因LmCesA1、LmCesA3、LmCesD1、LmCesE1和LmCesI1可以被溴氰菊酯诱导,表明其可能参与飞蝗对溴氰菊酯的代谢解毒及抗性产生。     

Sub-lethal effects of deltamethrin residues on the within-crop behaviour and distribution ofCoccinella septempunctata

The behaviour and distribution of adultCoccinella septempunctata L. (Coleoptera: Coccinellidae) were recorded in two plots of winter wheat infested with the cereal aphidsSitobion avenae (F.) andMetopolophium dirhodum (Walk.) (Homoptera: Aphididae). One plot was sprayed with the pyrethroid insecticide deltamethrin at a rate of 6.25 g a.i./ha and the other was left unsprayed. Single ladybird beetles were released sequentially on the ground at the centre of the sprayed and unsprayed plots and their behaviour and position in the crop canopy were recorded at 30 second intervals for a total of 15 min per beetle. Assessments, with fresh beetles, continued for four days after spray application with a total of eighty ladybird beetles observed. The 15 min period was selected to avoid lethal effects and no ladybird beetles were killed or knocked down as a result of exposure to deltamethrin residues during this period. Significant differences were found between the overall behaviour patterns ofC. septempunctata in the untreated and deltamethrin treated plots up to three days after the spray application. Ladybird beetles exposed to deltamethrin residues were observed to walk and groom significantly more frequently and to rest significantly less frequently than those in the unsprayed plot. Significant differences were also found between the observed distribution of ladybird beetles in the sprayed and unsprayed crop canopies, with higher numbers of observations towards the bottom of the crop canopy and on the ground in the deltamethrin treated plot than in the untreated plot during the first two days after deltamethrin application. Upon the foliage itself, ladybird beetles were observed significantly more frequently on the abaxial leaf surface in the deltamethrin treated crop compared with the untreated crop. The results are discussed in terms of possible evidence for the repellency of deltamethrin toC. septempunctata and also the implications for integrated pest management of changes in predator behaviour and crop distribution resulting from sub-lethal uptake of insecticides.     

敏感和抗性棉铃虫对溴氰菊酯毒力反应的机理研究

通过生物测定和生物化学方法比较了棉铃虫玎Helicoverpa armigera敏感和抗性种群对溴氰菊酯毒力反应及其3种解毒酶的差异。结果表明,田间抗性种群和室内药剂汰选的抗性种群对溴氰菊酯均有较高的抗性,其抗性倍数分别达到195.8和37 375倍。水解酯酶和多功能氧化酶是导致棉铃虫对溴氰菊酯产生高抗性的重要酶系。特异性抑制剂活体内外抑制作用测试发现,敏感种群和抗性种群均含有较高量的乙酰胆碱酯酶,但两个种群对抑制剂的亲和力反应不同,表明乙酰胆碱酯酶在敏感种群和抗性种群中发生了不同的变化,这种变化可能与棉铃虫对溴氰菊酯的抗性有关。由此推断,棉铃虫对拟除虫菊酯这类中枢神经系统神经毒剂产生抗性,乙酰胆碱酯酶发生变化可能也是一个重要因子。     

亚致死剂量杀虫剂对意蜂工蜂嗅觉敏感性的影响

喙伸反应(PER)试验适用于评价杀虫剂对蜜蜂行为的影响。本实验利用喙伸反应研究了亚致死剂量(LD50/100～LD50/10)溴氰菊酯和吡虫啉对意蜂Apis mellifera ligustica L.工蜂嗅觉敏感性的影响。结果发现,经口饲喂溴氰菊酯5ng和10ng后,工蜂对0.1%的蔗糖溶液的敏感性显著下降(P<0.05),水应激指数降低,但对0.3%,1%,3%,10%和30%的蔗糖溶液的敏感性没有显著变化;而经口饲喂吡虫啉0.3ng和0.6ng后,工蜂对上述各浓度蔗糖溶液的敏感性变化不明显,但其水应激指数升高。     

Callus tissue of Solanum tuberosum L. cultured in the presence of the pyrethroid deltamethrin

The effect of Decis (deltamethrin as active ingredient) on callus tissue of Solanum tuberosum L. cv. Désirée was studied. Decis is an agrochemical currently used on field grown potato plants to control the Colorado beetle, a potato pest. Deltamethrin added to the culture medium interferes with the behaviour of callus tissue. After 5 h of culture, the level of total proteins was higher in treated tissue than in the control, and SDS-PAGE showed that deltamethrin promoted the increase of some soluble proteins. After 24 h and 14 days of culture, the level of total proteins became similar in both treated and control material. This similarity between control and treated tissues, after 14 days of culture, occurred as a result of the treatment with deltamethrin which caused a decrease of soluble proteins, but an increase in insoluble proteins whereas the opposite was observed for control callus. SDS-PAGE of both soluble and insoluble proteins showed that only quantitative dissimilarities occurred. This longer treatment also increased the chlorophyll content. Ultrastructural study of the cells revealed that tissue callus cultured for 14 days in the presence of deltamethrin had plastids containing a more developed membranous system, with a higher number of grana and with more compartments than in control cells. Deltamethrin also promoted the abundance of vesicles associated with dictyosomes. This response of the callus tissue to Decis added to the callus medium parallels the behaviour of potato plants treated with this agrochemical under field conditions (Fidalgo, Santos & Salema, 1993).     

Comparative insecticidal power of three pyrethroids on netting

Adult mosquitoes, Anopheles gambiae Giles and Culex quinquefasciatus Say (Diptera: Culicidae), were exposed for 3 min to replicate samples of polyester netting cut from replicate bednets treated with pyrethroid insecticide formulations at the recommended concentration (alphacypermethrin SC at 40mg ai/m2; cyfluthrin EW at 50 mg ai/m2; deltamethrin WT at 25 mg ai/m2), or treated with only a quarter of those dosages. After 4 months domestic use of the bednets in Malawi, chemical assays showed that pyrethroid deposits on the netting were somewhat less than the target concentrations. Comparing the pyrethroid bioassay results with Anopheles at both treatment concentrations, deltamethrin gave significantly higher mortality (99.7-100%) than the other compounds (alphacypermethrin 94-96%, cyfluthrin 80-89%). Culex bioassay mortality was lower (alphacypermethrin 56-74%; cyfluthrin 63-65%; deltamethrin 50-81 %) and results with the three pyrethroid insecticides at their recommended doses did not differ significantly.     

Further evidence that deltamethrin-impregnated collars protect domestic dogs from sandfly bites

In many foci of zoonotic visceral leishmaniasis (ZVL), domestic dogs are important reservoir hosts of the causative Leishmania parasites transmitted by phlebotomine sandflies (Diptera: Psychodidae). We tested the protective value of impregnated dog collars (20 g plastic containing deltamethrin 800 mg ai) against Phlebotomus papatasi (Scopoli) sandflies in Iran. For each assay, the dog was sedated and caged in a net with 70-100 wild-caught sandflies overnight (23.30-06.30 hours). Dogs wearing the collars were bitten by approximately 80% fewer sandflies than before collars were fitted, i.e. 51% vs. 11% of hungry female flies exposed. Sandfly mortality rates following 20 h exposure to dogs with collars (18%) or without collars (17%) were not significantly different. Effects of collars were tested when dogs had been wearing them for 8 days. A previous trial against the sandfly P. perniciosus Newstead in France, using smaller dogs, showed that effects of such collars were not fully realized until they had been worn for 2 weeks or more; they remained effective for at least 8 months and killed significant proportions of the sandflies exposed. Present results with P. papatasi, confirming that this simple device provides effective protection against sandflies, are considered sufficiently encouraging to justify a community-wide field trial of deltamethrin-impregnated dog collars against ZVL vector sandflies in Iran.