六种阳离子助剂对阿维菌素的增效作用

采用浸虫法和叶片药膜法比较了6种阳离子助剂与阿维菌素混用对小菜蛾Plutella xylostella 3龄幼虫的增效作用,并通过测定助剂对阿维菌素药液物理性状的影响以及助剂对小菜蛾体内超氧化物歧化酶(superoxide dismutase,SOD)、过氧化氢酶(catalases,CAT)和过氧化物酶(peroxidases,POD) 3种保护酶活性的影响等方面对其增效机制进行了初步分析,为阳离子助剂在杀虫剂领域的开发提供一定的依据。结果表明： 在400 mg/L以下,各阳离子助剂单独使用对小菜蛾3龄幼虫均无生物活性,但可明显提高阿维菌素对小菜蛾的药效。两种方法中,浸虫法的增效作用大于叶片药膜法,其中松香酸铜、1427和412103对阿维菌素的增效倍数分别为3.71、2.82和2.72。6种助剂均可明显降低阿维菌素药液的表面张力和接触角及增加药液在甘蓝叶片上的沉积量,但不同助剂间及相同助剂不同浓度间差异虽大多显著; 与增效比结果综合分析表明,助剂的润湿性能与其增效作用之间关系不大。阿维菌素药液分别加入松香酸铜、1427和412103后使试虫体内POD和SOD的活性明显提高,从侧面说明这3种助剂对虫体更具渗透性。     

棉铃虫核型多角体病毒与化学杀虫剂和卵磷脂混用的增效作用

棉铃虫核型多角体病毒(HaNPV)分别与三氟氯氰菊酯、溴氰菊酯、氰戊菊酯、灭净菊酯、灭多威、辛硫磷、甲基对硫磷和乙酰甲胺磷等化学杀虫剂混合饲喂棉铃虫幼虫,统计致死中浓度LC₅₀,计算增效比,测定虫体内与抗性有关的三种重要酶：多功能氧化酶(MFO)、羧酸酯酶(CarE)、乙酰胆碱酯酶(AChE)的活性。研究大豆卵磷脂对HaNPV致病性的影响。结果表明：HaNPV与化学杀虫剂混合饲喂抗性棉铃虫,生测统计增效比均大于1.0,特别是病毒与甲基对硫磷混用,增效比更是达到3.53,表现出良好的增效作用。混剂感染抗性棉铃虫,虫体内MFO的活性比化学杀虫剂单用时降低3～12倍,CarE和AChE的活性也比化学杀虫剂单用时低,HaNPV明显抑制了化学杀虫剂对MFO和CarE的诱导作用。HaNPV与大豆卵磷脂混用,提高了HaNPV对棉铃虫的感染致死率,缩短了致死中时间(LT₅₀)。     

农药助剂对茚虫威防治番茄潜叶蛾的减量增效作用

为评价农药助剂对15%茚虫威悬浮剂防治番茄潜叶蛾Tuta absoluta(Meyrick)的减量增效作用,分别向减量10%、20%、30%的15%茚虫威悬浮剂药液中添加500 ppm的有机硅silwet 408、矿物油、芦荟精油助剂,测定其对番茄潜叶蛾的田间防效。结果显示：相同浓度下,添加农药助剂后的防效均显著高于15%茚虫威悬浮剂的防效,相对常规用量通过添加有机硅Silwet 408、矿物油或芦荟精油可使农药减量10%～20%。田间应用将15%茚虫威悬浮剂按照常规用量减量10%～20%,通过添加有机硅Silwet 408、矿物油或芦荟精油可有效防治番茄潜叶蛾。     

氰氟虫腙对草地贪夜蛾的毒力与田间防效

【目的】本研究旨在明确氰氟虫腙对草地贪夜蛾Spodoptera frugiperda幼虫的毒力水平和田间防治效果,为科学使用氰氟虫腙防治草地贪夜蛾提供参考依据。【方法】采用饲料混毒法在室内测定了氰氟虫腙与4种常用杀虫剂甲维盐、氯虫苯甲酰胺、虱螨脲和茚虫威对草地贪夜蛾3和6龄幼虫的致死中浓度(LC₅₀)及LC₉₀值,以及LC₉₀浓度的这些杀虫剂对3龄幼虫的致死中时(medium lethal time, LT₅₀)值。采用人工喷雾方法测定了玉米田中22%氰氟虫腙悬浮剂(6.6 g/667 m²)、22%氰氟虫腙悬浮剂(17.6 g/667 m²)、5.7%甲维盐水分散剂(1 g/667 m²)和150 g/L茚虫威悬浮剂(2 g/667 m²)对草地贪夜蛾幼虫的防效。【结果】室内生测结果显示,供试的5种杀虫剂中氰氟虫腙对草地贪夜蛾3和6龄幼虫均具有较高的毒力,其LC₅₀值分别为2.64和4.3...     

渗透剂对高效氯氰菊酯毒力和三种鳞翅目害虫上表皮超微结构的影响

以甜菜夜蛾Spodoptera exigua (Hübner)、小菜蛾Plutella xylostella (L.)和棉铃虫Helicoverpa armigera (Hübner)为试虫,通过室内生物测定技术,研究了氮酮、噻酮和N-甲基-2-吡咯烷酮等3种渗透剂对高效氯氰菊酯毒力的影响;利用扫描电镜观察了甜菜夜蛾和小菜蛾4龄幼虫对照组和渗透剂处理组间上表皮超微结构的变化。结果表明：含3.0% N-甲基-2-吡咯烷酮的高效氯氰菊酯对小菜蛾幼虫LD₅₀为0.0074 μg/头、毒力系数为2.0,对高效氯氰菊酯增效作用明显,而对其他两种试虫没有增效作用;氮酮和噻酮对高效氯氰菊酯对3种鳞翅目幼虫毒力均无增效作用。甜菜夜蛾对照组上表皮蜡质层和护蜡层清晰可见,渗透剂处理组上表皮护蜡层有不同程度的消失;而小菜蛾对照组和N-甲基-2-吡咯烷酮处理组上表皮护蜡层没有明显变化,只有氮酮处理组上表皮的护蜡层消失。以上结果提示,渗透剂对上表皮护蜡层的影响不是其对高效氯氰菊酯增效作用的机制。     

三种喷雾助剂与杀虫剂混配防治烟粉虱的减量增效作用

[目的]为明确强力源、有机硅和怀农特3种喷雾助剂对吡虫啉、阿维菌素、苦参碱的减量增效作用.[方法]采用浸虫浸叶法和喷雾法开展烟粉虱Bemisia tabaci室内毒力测定和田间药效试验.[结果]3种喷雾助剂对3种药剂的增效作用从高到低依次为强力源＞有机硅＞怀农特.施用吡虫啉、阿维菌素和苦参碱48 h后,烟粉虱若虫的LC50分别为37.7146、1.8062和10.5632 mg/L,添加强力源后烟粉虱若虫LC50分别降低到13.0188、1.0990和2.7116 mg/L;添加有机硅后烟粉虱若虫LC50分别降低到16.1900、1.2719和3.1609 mg/L;添加怀农特后LC50分别降低到20.0851、1.3247和3.7603 mg/L.田间试验结果表明,3种药剂减量20％和30％添加3种喷雾助剂均显著高于3种单剂的防效,3种药剂减量40％添加强力源和有机硅对烟粉虱的防效显著高于每种单剂,添加怀农特略高于或者与每种单剂的防效持平.施药后3d,各处理对烟粉虱的防效达到最高,吡虫啉、阿维菌素、苦参碱减量20％添加强力源对烟粉虱的防效分别高达97.11％、90.83％、88.17％.施药7d后吡虫啉减量40％添加3种喷雾助对烟粉虱的防效仍保持在75.55％-80.76％,阿维菌素减量40％添加3种喷雾助剂保持在71.84％-79.12％,苦参碱减量40％添加3种喷雾助剂保持在68.60％-75.74％.[结论]3种药剂的常规用量减量20％-30％,并通过添加强力源、有机硅和怀农特3种喷雾助剂可提高对烟粉虱的防治效果.     

溴氰虫酰胺亚致死剂量对甜菜夜蛾生长发育及体内解毒酶活性的影响

【目的】探讨溴氰虫酰胺对甜菜夜蛾 Spodoptera exigua (Hübner)的亚致死效应,为甜菜夜蛾的综合防治和溴氰虫酰胺的合理使用提供理论依据。【方法】采用饲料混毒法,测定溴氰虫酰胺对甜菜夜蛾3龄幼虫的毒力,确定其亚致死剂量（LC₁₀和LC₂₅）,并分别用该亚致死剂量处理甜菜夜蛾3龄幼虫,研究其对甜菜夜蛾的生长发育和体内3种解毒酶活性的影响。【结果】以LC₁₀ 和LC₂₅剂量处理甜菜夜蛾3龄幼虫后,幼虫生长受到显著抑制,虫重抑制率分别为11.55%和27.68%;LC₁₀和LC₂₅处理组3龄幼虫到化蛹天数分别比对照组延长0.07和0.20 d;化蛹率显著低于对照组（80.93%）,分别为63.89%和49.43%;成虫寿命显著缩短1.11 d和2.08 d;单雌产卵量和卵孵化率也低于对照组。亚致死剂量溴氰虫酰胺处理甜菜夜蛾幼虫后24-96 h,羧酸酯酶活性和谷胱甘肽-S转移酶活性表现出相似的变化趋势,呈先激活升高、后被抑制降低;而多功能氧化酶活性在药剂处理48 h和72 h均受到不同程度的抑制作用,这种抑制作用与浓度成正比。【结论】亚致死剂量的溴氰虫酰胺对甜菜夜蛾的生长发育有显著抑制作用,对其幼虫体内解毒酶活性也有不同程度的抑制作用。     

甜菜夜蛾对虫酰肼的抗性选育、风险评估及交互抗性

虫酰肼是目前防治甜菜夜蛾Spodoptera exigua（Hübner）的一种主要杀虫剂,为评估其抗性风险,在室内进行了抗性筛选和交互抗性的研究。采用饲料感染法,在甜菜夜蛾饲养75代期间用虫酰肼筛选62代,与起始种群相比抗性上升39.2倍,与室内敏感品系相比抗性上升141.3倍。在筛选的早、中、后期,现实遗传力h²分别为0.1075（F₀～F₂₅）、0.2780（F₂₆～F₅₀）和0.0538（F₅₁～F₇₅）,整个筛选62代现实遗传力为0.1556。抗性种群筛选43次（F55）后停止用药筛选,饲养21代后,与敏感品系相比,抗性水平由63.5倍下降到21倍,抗性下降3倍。说明甜菜夜蛾具有对虫酰肼产生抗性的风险,且抗性衰退缓慢,短期内很难恢复到敏感水平。交互抗性测定结果表明,上述室内选育的抗性品系对甲氧虫酰肼具有71.4倍的高水平交互抗性,对阿维菌素具有13.1倍的中等水平交互抗性,对甲维盐、茚虫威和呋喃虫酰肼分别具有7.0、8.4和4.7倍的低水平交互抗性,但对溴虫腈交互抗性不明显（1.9倍）。结果提示： 间断交替使用虫酰肼可以延缓抗性的发展,但除溴虫腈外,虫酰肼和其他几种新型杀虫剂之间的轮用可能不是甜菜夜蛾抗性治理的有效策略。     

八种杀虫剂对韭菜迟眼蕈蚊发育和繁殖的亚致死效应

用胃毒触杀法确定8种常用杀虫剂对韭菜迟眼蕈蚊Bradysiaodoriphaga 3龄幼虫的LC₂₀和LC₅₀剂量后,以其LC₂₀分别处理3龄幼虫,将存活幼虫正常饲养,测定该剂量药剂对韭菜迟眼蕈蚊化蛹率、蛹重、羽化率,成虫存活率、雌雄比、单雌产卵量及卵孵化率等指标的影响。结果表明:毒死蜱等4种药剂的影响较显著,其影响程度由高到低依次为毒死蜱＞辛硫磷＞阿维菌素溴虫腈;而另4种药剂丙硫克百威、灭多威、丁硫克百威和吡虫啉则影响不显著。此外也测定了用后4种药剂LC₅₀剂量处理的存活试虫的上述生物学指标,结果表明：除化蛹率和羽化率较对照降低且差异显著外,其他生物学指标与对照处理无明显变化。     

Pb2+在甜菜夜蛾体内的积累及对种群的影响

重金属的污染及其治理是目前倍受关注的生态学问题之一.甜菜夜蛾是我国长江流域及以南地区蔬菜、棉花等作物上的主要害虫,近几年突发趋势明显.本文以甜菜夜蛾为靶标对象,设计5个浓度(0.3、1.2、4.8、19.2、76.8 mg · kg^-1)重金属Pb²⁺处理,探讨处理后甜菜夜蛾各虫态体内Pb²⁺的积累和排泄,并根据甜菜夜蛾各虫态的生长与存活情况,构建了该虫连续3个世代的种群生命表.结果表明: 取食含有不同浓度Pb²⁺的人工饲料后,各虫态甜菜夜蛾体内Pb²⁺的浓度在同一世代不同处理间存在显著差异,且呈显著的剂量 反应关系.各虫态体内Pb²⁺的浓度基本上随胁迫世代数的延长而增加.受Pb²⁺胁迫后,各虫态体内Pb²⁺的浓度顺序为5龄幼虫＞成虫＞蛹;该虫可通过粪便、预蛹蜕和蛹壳排泄体内部分重金属,且粪便和预蛹蜕中的Pb²⁺浓度远大于蛹蜕中的浓度;根据Pb²⁺不同浓度条件下甜菜夜蛾各虫态的存活率、雌性比和产卵量,构建的种群生命表表明,低浓度Pb²⁺胁迫可促进甜菜夜蛾的种群增长,而高浓度胁迫使种群增长衰退;且随着重金属的持续胁迫,其种群衰退更明显.研究结果为长期、客观评价重金属的危害性以及对重要农业害虫的种群影响提供了借鉴.     

Co-expression and Synergism Analysis of Vip3Aa29 and Cyt2Aa3 Insecticidal Proteins from Bacillus thuringiensis

Vegetative insecticidal protein (Vip3) from Bacillus thuringiensis shows high activity against lepidopteran insects. Cytolytic δ-endotoxin (Cyt) also has high toxicity to dipteran larvae and synergism with other crystal proteins (Cry), but synergism between Cyt and Vip3 proteins has not been tested. We analyzed for synergism between Cyt2Aa3 and Vip3Aa29. Both cyt2Aa3 and vip3Aa29 genes were co-expressed in Escherichia coli strain BL21 carried on vector pCOLADuet-1. Vip3Aa29 showed insecticidal activity against Chilo suppressalis and Spodoptera exigua, with 50% lethal concentration (LC(50)) at 24.0 and 36.6 μg ml(-1), respectively. It could also inhibit Helicoverpa armigera growth, with 50% inhibition concentration at 22.6 μg ml(-1). While Cyt2Aa3 was toxic to Culex quinquefasciatus (LC(50): 0.53 μg ml(-1)) and Chironomus tepperi (LC(50): 36 μg ml(-1)), it did not inhibit C. suppressalis, S. exigua, and H. armigera. However, the co-expression of Cyt2Aa3 and Vip3Aa29 showed synergistic effect on C. suppressalis and S. exigua, and the individual activities were strengthened 3.35- and 4.34-fold, respectively. The co-expression had no synergism against C. tepperi and H. armigera, but exerted some antagonistic effect on Cx. quinquefasciatus. The synergism between Cyt2Aa and Vip3Aa was thus discovered for the first time, which confirmed that Cyt toxin can enhance the toxicity of other toxins against some non-target insects. By synergism analysis, the effectiveness of microbial insecticides can be verified.     

The synergistic activity between Cry1Aa and Cry1c from Bacillus thuringiensis against Spodoptera exigua and Helicoverpa armigera

AIMS: To investigate the interaction between two crystal proteins, Cry1Aa and Cry1C, for future development of biopesticides based on Bacillus thuringiensis, toxicities of the two individual proteins and in combinations have been determined against Spodoptera exigua and Helicoverpa armigera larvae, and synergism between the proteins has been evaluated using synergistic factor. METHODS AND RESULTS: SDS-PAGE showed that Cry1Aa and Cry1C proteins could be expressed in acrystalliferous B. thuringiensis 4Q7 strain, with molecular weights of 135 and 130 kDa respectively. The bioassay results indicated a synergistic activity between Cry1Aa and Cry1C against S. exigua and H. armigera, and the highest toxicities could be observed in the combination of Cry1Aa and Cry1C at a ratio of 1 : 1. CONCLUSION: The two toxins, Cry1Aa and Cry1C, interact synergistically to exhibit higher toxicity against S. exigua and H. armigera. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the investigation on the synergistic activity between two B. thuringiensis Cry1 toxins. It can be applied to the rational design of new generations of B. thuringiensis biopesticides and to strategies for management of resistant insects.     

The toxicity of Bacillus thuringiensis 9816C to Spodoptera exigua related to the binding sites on BBMV

Abstract The binding and pore formation properties of toxins derived form Bacillus thuringiensis 9816C were analyzed by using brush border membrane vesicles (BBMV) of Spodoptera exigua and Helicoverpa armigera , and the results were compared to the results of toxicity bioassays. The strain 9816C is highly toxic to both S. exigua and H. armigera , whereas HΔ-73, which only produces Cry1Ac, is merely effective for H. armigera. Ligand blot experiment performed with peroxidase-labeled toxins revealed that the toxins of the two strains had the same binding sites as H. armigera BBMV and different binding sites from S. exigua BBMV. The toxins of Bt 9816C bind to a 210-kDa protein of S. exigua BBMV, while Cry1Ac cannot recognize this binding site. Both toxins were tested for the ability to alter the permeability of S. exigua BBMV, as measured by a light scattering assay. The toxins of Bt 9816C, which is toxic to S. exigua , permeabilized BBMV, whereas Cry1Ac did not. These results suggest that the specific binding site recognized by Bt 9816C toxins is responsible for its high toxicity against Spodoptera exigua.     

Synergism of diacylhydrazine insecticides with metyrapone and diethylmaleate

Abstract:  The two metabolic synergists, metyrapone (2-methyl 1,2-di-3-pyridyl-1-propanone) and diethylmaleate could increase the toxicity of the three most recent diacylhydrazines, representing a novel group of insect growth regulators (IGRs). These components are known as respective inhibitors of oxidative and glutathione S-transferase enzymes. Larvicidal toxicity was tested in the laboratory by oral treatment against last-instar larvae of the Colorado potato beetle Leptinotarsa decemlineata (Say) and of the beet armyworm Spodoptera exigua (Hübner). The obtained results should enable to improve the activity of tebufenozide, methoxyfenozide and halofenozide, and it may be used to suggest potential mechanisms for resistance against this novel group of IGRs, that is important to counteract cross-resistance with other insecticide groups.     

Organophosphorus insecticides synergize pyrethroids in the resistant strain of cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) from West Africa

Helicoverpa armigera (Hübner) populations from West Africa recently developed resistance to pyrethroid insecticides through enhanced metabolism by mixed-function oxidases. The combination index method was used to study the synergism of pyrethroids by organophosphorus insecticides. Several mixtures of insecticides currently registered to control cotton pest complex in West Africa were tested, including: cypermethrin/ethion, cypermethrin/profenofos, deltamethrin/ triazophos, deltamethrin/chlorpyriphos, cyfluthrin/chlorpyriphos, and betacyfluthrin/chlorpyriphos. In the resistant strain, the organophosphorus insecticides significantly increased the toxicity of pyrethroids suppressing the resistance effect, either by additive or synergistic effects. Significant synergism was shown for the following mixtures: cypermethrin/ethion, deltamethrin/triazophos, and deltamethrin/chlorpyriphos. The use of synergism from these insecticide mixtures should prove to be an additional tool in the overall resistance management strategy because the pyrethroid resistance in H. armigera from West Africa is not yet stable, decreasing between cotton seasons and increasing with treatments. In absence of selection, the susceptibility of H. armigera to insecticides should be restored.     

Effect of biological and chemical insecticides on Spodoptera species (Lep., Noctuidae) and marketable yields of tomatoes

Various biological and chemical insecticide treatments were evaluated against beet armyworm Spodoptera exigua (Hübner), yellowstriped armyworm Spodoptera ornithogalli (Guenée) and southern armyworm Spodoptera eridania (Cramer) to determine their effects on Spodoptera species, fruit quality and marketable yields of tomatoes Lycopersicon esculentum Mill. Biological insecticides included several Bacillus thuringiensis (Berliner) products including Condor^® OF, Dipel^® 2X, Javelin^® WG, Bactec^® III, Biobit^® FC, Cutlass^® WP and Lepinox^® G. Other biological treatments included a baculovirus, SeNPV isolated from S. exigma , and an entomophagous nematode, Steinernema carpocapsae Weiser. Chemical treatments consisted of several insecticides from various classes including a carbamate (methomyl), pyrethroid (fenpropathrin) and an organophosphate (chlorpyrifos). A natural extract from the neem tree azadirachtin and an untreated control were also included in the evaluation studies. Population densities of S. exigua were below the economic threshold level in control plots and there were no significant differences for small, medium and large larvae. Densities of S. ornithogalli and S. eridania larvae exceeded the threshold level and significant treatment differences were observed in their populations. Fruit injuries were significantly higher in nonefficacious treatments that included S. carpocapsae , SeNPVs and untreated controls. Average weight per fruit was not significantly affected by treatment rates of applications, but total marketable yields were significantly higher in efficacious biological, chemical and combination treatments compared with the control.     

Compatibility and interaction between Bacillus thuringiensis and certain insecticides: perspective in management of Tuta absoluta (Lepidoptera: Gelechiidae)

Bacillus thuringiensis var. kurstaki (Berliner) (Bt) has been suggested as a biological control agent for Tuta absoluta (Meyrick). The objective of this study was to determine the interaction between abamectin, azadirachtin, indoxacarb, chlorantraniliprole, dichlorvos and metaflumizone with Bt. Effect of recommended doses of the chemical insecticides on colonisation of Bt was also investigated in culture medium. Except for metaflumizone, none of the chemicals tested reduced the colonisation of Bt compared with control. Interaction between Bt and the chemical insecticides on 2nd-instar larvae was also assessed. In interaction tests, Bt was applied at LC₅₀ level, 0, 12, 24 or 36 h after treating the larvae with LC₁₀ or LC₂₅ of the chemical insecticides. An antagonistic effect was observed in all treatments where Bt was applied immediately after the chemical insecticide. Also, antagonism was observed when treatment with Bt was done 12 h after azadirachtin and metaflumizone applications. Applying Bt 12 and 24 h after treatment with LC₂₅ of chlorantraniliprole, dichlorvos and abamectin resulted in synergism. But, synergism with LC₁₀ of dichlorvos and abamectin was observed only after 12 h. Additive effect was observed in the rest of the time and concentration combinations. Based on the results obtained, simultaneous use of the chemical insecticides tested and Bt is not recommended for T. absoluta control; and an appropriate time interval should be taken into consideration accordingly.     

Evaluating new insecticides for the control of Helicoverpa spp. (Lepidoptera: Noctuidae) on capsicum and zucchini

Abstract  The efficacy of insecticides in controlling Helicoverpa spp., predominantly H. armigera (Hübner), on capsicum and zucchini was tested in small plot trials. Indoxacarb, methoxyfenozide, spinosad, emamectin benzoate and novaluron provided control, as measured by the percentage of damaged fruit, equal to or better than standard treatments of methomyl or methomyl alternated with methamidophos on capsicum. The Helicoverpa nucleopolyhedrovirus gave control equivalent to the standard treatment, as did Bacillus thuringiensis aizawai , but B. thuringiensis kurstaki was ineffective. Helicoverpa armigera larvae were present in zucchini flowers but did little damage to the fruit. None of the insecticides significantly reduced the percentage of damaged zucchini fruit compared with the untreated control. Bifenthrin, spinosad, emamectin benzoate and methoxyfenozide were effective in controlling larvae in flowers, while methomyl, B. thuringiensis aizawai , B. thuringiensis kurstaki and novaluron were not effective. Data indicated that all the insecticides effectively controlled larvae of Diaphania indica (Saunders), cucumber moth, in the zucchini flowers. There has been a limited range of insecticides available to manage Helicoverpa spp. in these vegetable crops, but these trials demonstrate the effectiveness of a number of newer insecticides that could be used and that would be compatible with integrated pest management programs in the crops.