不同施药方式对福建烟蚜抗药性及活性酶的影响

本文采用连续施用和轮换施用农药方式对福建烟区烟蚜进行抗药性及其体内酶变化的测定,研究结果表明,在连续施用3次、5次、7次和9次后,施用灭多威后的烟蚜抗性分别增长了1.397倍、2.608倍、4.891倍和7.598倍;施用吡虫啉则分别增长了1.717倍、2.114倍、2.861倍和4.169倍;施用高效氯氟氰菊酯则分别增长了1.341倍、2.577倍、5.277倍和10.767倍.经过1次、2次、3次和4次的农药轮用顺序施用后,烟蚜对灭多威的抗性指数分别增长了1.522倍、1.661倍、1.839倍和2.196倍;对高效氯氟氰菊酯分别增长了1.490倍、1.603倍、1.742倍和1.898倍;对吡虫啉分别增长了1.716倍、1.980倍、2.259倍和2.519倍.     

云南烟蚜抗药性机制研究

通过比较云南烟蚜敏感品系和抗性品系的解毒酶(α-乙酸萘酯羧酸酯酶、β-乙酸萘酯羧酸酯酶)和靶标酶(乙酰胆碱酯酶)的活力,研究了烟蚜对有机磷、拟除虫菊酯和氨基甲酸酯类杀虫剂抗性的生化机制,并通过酯酶基因扩增检测和钠离子通道突变检测,研究了其抗性的分子机制。结果表明:α-乙酸萘酯羧酸酯酶活力增强是烟蚜对有机磷类、氨基甲酸酯类杀虫剂及拟除虫菊酯类杀虫剂的抗性机制之一;乙酰胆碱酯酶在烟蚜对有机磷杀虫剂抗性中起重要作用;3个抗性品系烟蚜均没有发生酯酶基因扩增,抗拟除虫菊酯品系烟蚜发生了钠离子通道突变。     

黑缘红瓢虫对6种杀虫剂的敏感性测定

用点滴法在室内初步测定3黑缘红瓢虫Chilocorus rubidusHope幼虫对敌敌畏、氰戊菊酯、氟氯氰菊酯、硫丹、氧化乐果、灭多威等6种果园常用杀虫剂的敏威性。结果表明:黑缘红瓢虫幼虫对6种杀虫剂的敏感性依次为:氰戊菊酯、氟氯氰菊酯、硫丹、氧化乐果、敌敌畏、灭多威。LD50按以下次序增大:灭多威,氟氯氰菊酯,氧化乐果,氰戊菊酯,敌敌畏,硫丹。可见,硫丹对黑缘红瓢虫毒力最小,是最安全。敌敌畏等有机磷杀虫剂对它的毒力也较低,而拟除虫菊酯类药剂对黑缘红瓢虫的毒力则很高。同种药剂对不同用药水平地区的黑缘红瓢虫成虫的毒力差异显著,黑缘红瓢虫对氟氯氰菊酯和氰戊菊酯分别产生了5.4和7.6倍的抗药性,是羧酸酯酶活性提高所致。不同种类杀虫剂对黑缘红瓢虫和朝鲜球坚蚧Didesmococcus koreanusBorchs的选择指数差异极为显著,依次为硫丹、灭多威、敌敌畏、氰戊菊酯、氧化乐果、氟氯氰菊酯,如硫丹为2.6,而氟氯氰菊酯仅为0.04。硫丹是防治抗性朝鲜球坚蚧比较理想的一种杀虫剂。     

黑缘红瓢虫对六种杀虫剂的敏感性测定

用点滴法在室内初步测定3黑缘红瓢虫Chilocorus rubidus Hope幼虫对敌敌畏、氰戊菊酯、氟氯氰菊酯、硫丹、氧化乐果、灭多威等6种果园常用杀虫剂的敏威性。结果表明：黑缘红瓢虫幼虫对6种杀虫剂的敏感性依次为：氰戊菊酯、氟氯氰菊酯、硫丹、氧化乐果、敌敌畏、灭多威。LD50按以下次序增大：灭多威,氟氯氰菊酯,氧化乐果,氰戊菊酯,敌敌畏,硫丹。可见,硫丹对黑缘红瓢虫毒力最小,是最安全。敌敌畏等有机磷杀虫剂对它的毒力也较低,而拟除虫菊酯类药剂对黑缘红瓢虫的毒力则很高。同种药剂对不同用药水平地区的黑缘红瓢虫成虫的毒力差异显著,黑缘红瓢虫对氟氯氰菊酯和氰戊菊酯分别产生了5．4和7．6倍的抗药性,是羧酸酯酶活性提高所致。不同种类杀虫剂对黑缘红瓢虫和朝鲜球坚蚧Didesmococcus koreanus Botchs的选择指数差异极为显著,依次为硫丹、灭多威、敌敌畏、氰戊菊酯、氧化乐果、氟氯氰菊酯,如硫丹为2．6,而氟氯氰菊酯仅为0．04。硫丹是防治抗性朝鲜球坚蚧比较理想的一种杀虫剂。     

福建主要烟区烟蚜抗药性及烟蚜体内酶的活性

本文通过测定建立了灭多威、辛硫磷、吡虫啉、氰戊菊酯、高效氯氟氰菊酯和啶虫脒6种药剂的敏感基线。测定了2009年福建南平、三明和龙岩烟区的烟蚜田间种群的抗药性水平以及烟蚜种群解毒酶与靶标酶的活性。结果显示：与2008年的监测结果相比较,灭多威对福建南平、三明和龙岩3个烟区的烟蚜种群的LC50分别增长了0．004倍、0．046倍和0．051倍;辛硫磷对福建南平、三明和龙岩3个烟区的烟蚜种群的Lc50分别降低了0．213倍、0．078倍和0．088倍;毗虫啉对福建南平、三明和龙岩3个烟区的烟蚜种群的LC50分别增长了1．186倍、1．328倍和0．56倍;氰戊菊酯对南平和龙岩烟区的烟蚜种群的Lc50分别增长了0．367倍和0．139倍,对三明烟区的烟蚜种群的Lc50降低了0．103倍;高效氯氟氰菊脂对南平和龙岩烟区的烟蚜种群的LC50分别增长了0．345倍和0．244倍,对三明烟区的烟蚜种群的Lc如降低了0．035倍;啶虫脒对福建南平、三明和龙岩3个烟区的烟蚜种群的Lc靳分别增长了O．498倍、0．724倍和0．868倍。由于3个烟区近几年大田防治烟蚜极少或没有使用灭多威、辛硫磷、氰戊菊酯和高效氯氟氰菊酯这4种杀虫剂,所以3个烟区的烟蚜种群对这4种杀虫剂的抗药性增加率降低或抗药性下降。目前除了南平烟区的烟蚜种群对啶虫脒产生了高抗（抗性倍数为6cL92倍）,其余烟区还未出现高抗种群。3个烟区烟蚜种群的3种酶活性差异明显,以三明种群最高,南平种群次之,龙岩种群最低。与2007年的测定结果相比较,三明、南平和龙岩的烟蚜种群CarE比活力分别增加了2．249倍、2．335倍和3．491倍;AChE比活力分别增加了0．336倍、0．664倍和0．782倍;GSTs比活力分别增加了0．591倍、0．811倍和1．447倍。     

云南主要烟区烟蚜种群解毒酶活力比较

通过测定烟蚜Myzus persicae(Sulzer)的α-NA羧酸酯酶、β-NA羧酸酯酶、谷胱甘肽转移酶和乙酰胆碱酯酶的活力,比较了云南5个主要烟区田间烟蚜种群的4种酶的活力频率分布,结果表明,云南5个烟区的烟蚜田间种群的α-NA羧酸酯酶、β-NA羧酸酯酶和乙酰胆碱酯酶的高活力个体均以楚雄和昆明种群较高,昭通种群和丽江种群较低.谷胱甘肽转移酶在5个烟区烟蚜种群间差异不大.     

河北转Bt基因棉田棉铃虫对杀虫剂的抗性及相关酶活性的变化

为明确河北省推广种植植转Bt基因抗虫棉（简称Bt棉）后, 棉铃虫Helicoverpa armigera (Hübner)对常用杀虫剂的抗药性水平及其生化机理, 2011-2012年采用点滴法对保定南郊、 沧州南皮、 邢台巨鹿3个地区的田间种群以及敏感种群进行了室内毒力测定, 并采用生化分析法对4个种群相关的羧酸酯酶（carboxylesterase, CarE）、 谷胱甘肽S 转移酶(glutathione S-transferases, GSTs)和乙酰胆碱酯酶(acetylcholinesterase, AChE)的活性进行了研究。结果表明: 3个田间种群对高效氯氰菊酯和氰戊菊酯处于中至高抗水平, 抗性倍数为20.02~73.70倍; 对灭多威处于低至中抗水平, 抗性倍数为6.27~11.84倍; 对高效氯氟氰菊酯(抗性倍数: 1.07~4.20倍), 辛硫磷、 毒死蜱和马拉硫磷(抗性倍数: 1.00~2.69倍), 以及氯虫苯甲酰胺（抗性倍数: 2.00~3.67倍）均处于敏感水平。3个田间种群的CarE, GSTs和AChE活性分别是敏感种群的1.06~1.23, 1.20~1.63和1.15~1.23倍, 这可能与其对高效氯氰菊酯、 氰戊菊酯和灭多威产生的抗性有关。     

湖南宁乡烟区烟蚜的抗性监测及其相关酶的活性测定

为明确湖南宁乡烟区烟蚜对杀虫剂的抗性现状,测定烟蚜田间种群对吡虫啉、啶虫脒、氯氟氰菊酯、辛硫磷及灭多威5种杀虫剂的敏感性。结果表明,烟蚜田间种群对烟碱类的啶虫脒和吡虫啉表现出中等抗性,与敏感品系相比,抗性倍数分别为25. 20和21. 03;对菊酯类的氯氟氰菊酯表现为低抗水平,抗性倍数为5. 19;对辛硫磷和灭多威均表现为敏感性降低,抗性倍数分别为2. 38和2. 86。本研究又测定了烟蚜田间与室内敏感种群相关酶活力的变化,结果表明,田间种群体内解毒酶、保护酶与消化酶活力均显著高于室内敏感种群。试验结果可为延缓田间烟蚜抗性及烟蚜的综合治理提供理论依据。     

不同施药方式对福建烟蚜抗药性及活性酶的影响

本文采用连续施用和轮换施用农药方式对福建烟区烟蚜进行抗药性及其体内酶变化的测定,研究结果表明,在连续施用3次、5次、7次和9次后,施用灭多威后的烟蚜抗性分别增长了1.397倍、2.608倍、4.891倍和7.598倍;施用吡虫啉则分别增长了1.717倍、2.114倍、2.861倍和4.169倍;施用高效氯氟氰菊酯则分别...     

棉铃虫抗药性的生理生化机制研究

本文报道了棉铃虫Helicoverpa armigera田间抗性种群对杀虫剂抗药性的生理生化机制。抗性种群(HJ-R)5龄幼虫羧酸酯酶、谷胱甘肽转移酶、多功能氧化酶活力均明显高于相对敏感种群(HD-S)。两种群乙酰胆碱酯酶对杀虫剂敏感性没有显著差异。HJ-R种群的腹神经索对氰戊菊酯表现了2-3倍的神经不敏感性。HJ-R种群对氨基甲酸酯类杀虫剂的抗性主要是由代谢机制引起,其中多功能氧化酶可能起主导作用;对菊酯的抗性是由多功能氧化酶、酯酶、以及神经不敏感性几个因子综合作用的结果。     

四种类型杀虫剂对麦长管蚜的温度效应及其与主要解毒酶的关系

为了明确杀虫剂毒力受温度的影响及其程度,本文测定了4大类8种药剂在10～25℃下对麦长管蚜的毒力;并测定了麦长管蚜Sitobion avenae(Fabricius)在不同温度下2个解毒酶和1个靶标酶的活性差异。结果表明,高效氯氰菊酯对麦长管蚜表现不规则负温度系数,啶虫脒表现不规则正温度系数,高效氟氯氰菊酯对麦长管蚜的毒力不受温度影响,其他药剂(辛硫磷、毒死蜱、灭多威、丁硫克百威、吡虫啉)均表现为明显的正温度系数效应,以有机磷类杀虫剂表现最为明显,毒死蜱温度系数高达57.70。酶活性实验表明:麦长管蚜在高温下GST活性增强,羧酸酯酶和乙酰胆碱酯酶活性降低。它们的变化规律表明:GST活性与负温度系数密切相关,正温度系数与羧酸酯酶活性和靶标酶乙酰胆碱酯酶活性有关。     

二点叶螨对甲氰菊酯、氧乐果和四螨嗪抗药性的选育、衰退和恢复

以兰州吐鲁沟公园的二点叶螨Tetranychusurticae为敏感品系 ,分别用氧乐果、甲氰菊酯、四螨嗪喷雾处理 15次 ,其抗性水平分别为 38 5、 479 8和 6 7 3倍。将抗性品系分别与敏感品系进行杂交和回交的结果表明 :抗氧乐果品系的显性系数DRS (R♀×S♂ )为 0 470 0、DSR (S♀×R♂ )为 0 4749;抗甲氰菊酯品系的DRS (R♀×S♂ )为 0 5 15 5 ,DSR 为0 5 2 37;抗四螨嗪品系的DRS为 0 3134 ,DSR 为 0 2 46 6。表明二点叶螨对这 3种药剂的抗性均是由单个不完全显性基因所控制。在连续 10个月不接触药剂的情况下 ,3个抗性品系的抗药性都有下降 ,抗氧乐果品系的抗性下降最快 ,只有敏感品系的抗性倍数的 3 6倍 ;抗甲氰菊酯种群的抗性下降较慢 ,为敏感品系的 95 9倍。再经甲氰菊酯、氧乐果、四螨嗪分别连续15次喷雾处理后 ,3个抗性种群的抗性水平又再度回升 ,抗甲氰菊酯品系回升较快 ,抗性为敏感品系的 5 2 3 5倍 ,抗四螨嗪品系次之 ,抗氧乐果的品系抗性恢复最慢。     

二点叶螨对甲氰菊酯、氧乐果和四螨嗪抗药性的选育、衰退和恢复

以兰州吐鲁沟公园的二点叶螨Tetranychus urticae 为敏感品系,分别用氧乐果、甲氰菊酯、四螨嗪喷雾处理15次,其抗性水平分别为38.5、479.8和67.3倍。将抗性品系分别与敏感品系进行杂交和回交的结果表明：抗氧乐果品系的显性系数DRS（R♀×S♂）为0.4700、D_SR（S♀×R♂）为0.4749;抗甲氰菊酯品系的DRS（R♀×S♂）为0.5155, DSR为0.5237;抗四螨嗪品系的DRS为0.3134, DSR为0.2466。表明二点叶螨对这3种药剂的抗性均是由单个不完全显性基因所控制。在连续10个月不接触药剂的情况下,3个抗性品系的抗药性都有下降,抗氧乐果品系的抗性下降最快,只有敏感品系的抗性倍数的3.6倍;抗甲氰菊酯种群的抗性下降较慢,为敏感品系的95.9倍。再经甲氰菊酯、氧乐果、四螨嗪分别连续15次喷雾处理后,3个抗性种群的抗性水平又再度回升,抗甲氰菊酯品系回升较快,抗性为敏感品系的523.5倍,抗四螨嗪品系次之,抗氧乐果的品系抗性恢复最慢。     

斜纹夜蛾抗性种群中酶抑制剂对杀虫剂的增效作用（英文）

采用浸液生测法研究了斜纹夜蛾Spodoptera litura巴基斯坦抗性种群中酶抑制剂［胡椒基丁醚（PBO）和脱叶膦（DEF)］对丙溴磷、灭多威、硫双灭多威、氯氰菊酯、氯氟氰菊酯、联苯菊酯、茚虫威和多杀菌素等杀虫剂的增效作用。结果表明：PPO和DEF对氨基甲酸酯杀虫剂灭多威和硫双灭多威均具有增效作用,但对有机磷杀虫剂丙溴磷不具有增效作用。两种抑制剂对氯氰菊酯均产生增效作用,但对联苯菊酯没有增效作用。PPO 和DEF增加了氯氟氰菊酯对Multan种群的毒性,但没有增加其对Mailsi种群的毒性。DEF对多杀菌素具有增效作用,但PBO对其没有增效作用。PBO和DEF对氨基甲酸酯杀虫剂、拟除虫菊酯杀虫剂、茚虫威和多杀菌素具有明显的增效作用,这说明细胞色素P450单加氧酶和酯酶的解毒作用至少部分参与了斜纹夜蛾对这些杀虫剂的抗性过程。不过,两种增效剂对杀虫剂增效作用范围有限,暗示对于斜纹夜蛾巴基斯坦种群而言,其他的机制（如靶位点不敏感、表皮穿透作用降低）可能是更重要的抗性机制。     

Spraying pyrethroid and neonicotinoid insecticides can induce outbreaks of <Emphasis Type="Italic">Panonychus citri</Emphasis> (Trombidiformes: Tetranychidae) in citrus groves

Panonychus citri (McGregor) (Trombidiformes: Tetranychidae) is one of the main defoliator mites in citrus groves. In Brazil, P. citri was formerly considered a secondary pest, but in recent years, the population levels of this mite have increased in many groves, requiring additional acaricide applications for its control. The population growth of P. citri is associated with the increase in the number of applications of pyrethroid and neonicotinoid insecticides to control insect citrus pests. This study assessed the effects of pyrethroid (deltamethrin, esfenvalerate, λ-cyhalothrin) and neonicotinoid (imidacloprid and thiamethoxam) insecticides on biological, behavioral and demographic parameters of P. citri. None of the insecticides tested affected larval hatching, but deltamethrin, esfenvalerate, and λ-cyhalothrin reduced the survival of larvae and protonymphs. Deltamethrin, esfenvalerate, and λ-cyhalothrin induced a significant increase in the fecundity of surviving females. Pyrethroids also caused repellency and changed feeding and oviposition preferences. In contrast, imidacloprid and thiamethoxam did not affect the survival of immature stages, but imidacloprid significantly increased fecundity. Imidacloprid and thiamethoxam did not cause any repellent effect or changes in the feeding and oviposition preferences. Based on the demographic parameters, deltamethrin, λ-cyhalothrin, and imidacloprid increased R_o, r, and λ, whereas esfenvalerate and thiamethoxam were similar to the control. Therefore, the use of these insecticides (especially deltamethrin, λ-cyhalothrin, and imidacloprid) requires caution, such as avoiding repeated use of these compounds during the periods of P. citri incidence in citrus groves.     

Total effects of contact and residual exposure of bifenthrin and λ-cyhalothrin on the predatory mite Galendromus occidentalis (Acari: Phytoseiidae)

Pyrethroid insecticides are generally regarded as acutely toxic to predatory phytoseiid mites; however, persistence of hull split spray pyrethroid residues on almond trees and their effects on phytoseiids have not been quantified over time. Hull split, the separation of the almond hull along the suture, exposes the new crop nuts to infestation by Amyelois transitella (Walker) larvae, and is the preferred timing for insecticides applied for their control. Galendromus occidentalis (Nesbitt) is the most important phytoseiid biocontrol agent for web-spinning spider mites in California (USA) almond orchards, and the impact of bifenthrin and λ-cyhalothrin pyrethroid residue on their survival, fertility, and fecundity was determined. The total effects of direct contact with esfenvalerate, permethrin, bifenthrin and λ-cyhalothrin were also evaluated for comparison. The total effects (E) of direct contact treatments of the four pyrethroids ranged from 77.8 % for esfenvalerate to 98.8 % for bifenthrin. Both bifenthrin and λ-cyhalothrin twig residue would be considered harmful (IOBC class 4) following field application at hull split timing. Bifenthrin twig residue would be considered slightly harmful (IOBC class 2) for up to 3.5 months and harmless (IOBC class 1) after 6 months. λ-cyhalothrin residue would be considered moderately harmful (IOBC class 3) for up to 3.5 months following application and harmless (IOBC class 1) after 6 months. Bifenthrin and λ-cyhalothrin twig residue on treated trees significantly reduced G. occidentalis female survival for up to 6 months post-treatment, however total effects (E) classify these residues as harmless (IOBC class 1) after 6 months. Harmful effects of direct and residual exposure following application have implications for the use of these pyrethroids in an integrated mite management program for perennial crops.     

桔小实蝇实验种群对敌百虫、高效氯氰菊酯和阿维菌素的抗性增长规律

桔小实蝇Bactrocera doralis (Hendel)是华南地区水果蔬菜上重要害虫,近年来暴发成灾,造成巨大的经济损失。使用化学杀虫剂是防治该虫的重要方法。在长期、频繁接触杀虫剂条件下该虫的抗药性产生、发展规律等问题值得深入研究。本文采用LC₅₀、LC_80-90两种剂量汰选成虫、幼虫,研究了桔小实蝇对敌百虫、高效氯氰菊酯和阿维菌素3种药剂的抗性增长规律。通过不接触药剂继代饲养获得了对3种杀虫剂的敏感品系,建立了毒力回归方程,明确了毒力敏感基线LC₅₀分别为1.6024 mg/L,3.0964 mg/L和0.6074 mg/L。不同药剂种类、不同汰选方式时桔小实蝇的抗药性发展速度是不同的。以成虫死亡率50%左右作为选择压力,桔小实蝇对敌百虫的抗性发展最快,汰选至14代抗性增长至84.6倍;其次是高效氯氰菊酯,抗性增长至27.1倍;而对阿维菌素的抗性仅上升至7.7倍 。在成虫和幼虫80%～90%死亡率左右的选择压力下,桔小实蝇对高效氯氰菊酯的抗性发展最快,汰选14代后抗性增长至125.4倍; 其次是敌百虫,抗性增大至49.9倍;对阿维菌素抗性增长相对较缓慢,11代后为17.9倍。在成虫80%～90%死亡率左右的选择压力下,汰选14代、14代、11代后桔小实蝇对高效氯氰菊酯、敌百虫、阿维菌素分别增大至58.7倍、37.6倍、11.9倍。对成虫、幼虫均进行汰选桔小实蝇抗药性发展更快。建立了不同汰选方式时桔小实蝇实验种群汰选代数与对3种杀虫剂的抗性程度之间的关系方程,其中高效氯氰菊酯、敌百虫处理符合韦布尔曲线模型,阿维菌素处理符合幂曲线方程。     

棉蚜抗氧化乐果品系的羧酸酯酶基因突变

用氧化乐果对室内敏感品系棉蚜Aphis gossypii (Glover)进行抗性选育,经24代筛选,抗性指数达到124.7倍。以α-乙酸萘酯（α-NA）为底物,比较了氧化乐果敏感和抗性品系棉蚜羧酸酯酶的比活力,发现抗性品系羧酸酯酶比活力明显小于敏感品系。对这两个品系的羧酸酯酶基因进行了克隆,通过对抗性和敏感品系羧酸酯酶基因核苷酸序列及推导的氨基酸序列比较,发现抗性品系有4个氨基酸残基发生了替代 (His¹⁰⁴→Arg, Ala¹²⁸→Val, Thr³³³→Asp, Lys⁴⁸⁴→Arg)。对其蛋白质三维结构分析推测只有His¹⁰⁴→Arg的替代是位于其活性中心。棉蚜氧化乐果敏感和抗性品系羧酸酯酶基因cDNA全长的GenBank登录号分别为AY485216和AY485214。     

Insecticide susceptibility and resistance of Blattella germanica (Blattaria: Blattellidae) in Seoul, Republic of Korea, 2007

The susceptibility of Blattella germanica (L.) in the Republic of Korea (ROK) to insecticides was evaluated under laboratory conditions using 12 insecticides currently used by the local public health centers and/or pest control operators in the ROK. The insecticides included seven pyrethroids and five organophosphates. Based on their LD₅₀ values, the order of susceptibility of B. germanica adults to the insecticides was chlorpyrifos-methyl, profenofos and chlorpyrifos with values of 0.07, 0.29 and 0.88 µg/♀, respectively. The least susceptibility was obtained with tetramethrin at LD₅₀ of 7.39 µg/♀. In the comparative resistance test, the resistance ratios (RR) of 12 insecticides were compared to each other using field-collected B. germanica adults in Seoul between 1993 and 2007. Blattella germanica demonstrated higher RRs to pyrethroids such as λ-cyhalothrin, and low RRs among the organophosphates. Among the pyrethroids, λ-cyhalothrin had the highest RRs of 111- and 129-fold differences at LD₅₀ and LD₉₀ values, respectively. Among the organophosphates, profenofos was observed to have the highest RRs of 4- and 15-fold differences at LD₅₀ and LD₉₀ values, respectively. However, there were no significant differences in susceptibility to tetramethrin, chlorpyrifos and fenitrothion. Blattella germanica was more susceptible to pyridafenthion showing a 0.7-fold difference in a resistance ratio (RRLD₅₀= LD₅₀ value of 2007/LD₅₀ value of 1993). Resistance ratio of tetramethrin was low, but susceptibility was also not high.     

Mutations in acetylcholinesterase genes of Rhopalosiphum padi resistant to organophosphate and carbamate insecticides.

Apple grain aphid, Rhopalosiphum padi (Linnaeus), is an important wheat pest. In China, it has been reported that R. padi has developed high resistance to carbamate and organophosphate insecticides. Previous work cloned from this aphid 2 different genes encoding acetylcholinesterase (AChE), which is the target enzyme for carbamate and organophosphate insecticides, and its insensitive alteration has been proven to be an important mechanism for insecticide resistance in other insects. In this study, both resistant and susceptible strains of R, padi were developed, and their AChEs were compared to determine whether resistance resulted from this mechanism and whether these 2 genes both play a role in resistance. Bioassays showed that the resistant strain used was highly or moderately resistant to pirimicarb, omethoate, and monocrotophos (resistance ratio, 263.8, 53.8, and 17.5, respectively), and showed little resistance to deltamethrin or thiodicarb (resistance ratio, 5.2 and 3.4, respectively). Correspondingly, biochemistry analysis found that AChE from resistant aphids was very insensitive to the first 3 insecticides (I50 increased 43.0-, 15.2-, and 8.8-fold, respectively), but not to thiodicarb (I50 increased 1.1-fold). Enzyme kinetics tests showed that resistant and susceptible strains had different AChEs. Sequence analysis of the 2 AChE genes cloned from resistant and susceptible aphids revealed that 2 mutations in Ace2 and 1 in Ace1 were consistently associated with resistance. Mutation F368(290)L in Ace2 localized at the same position as a previously proven resistance mutation site in other insects. The other 2 mutations, S329(228)P in Ace1 and V435(356)A in Ace2, were also found to affect the enzyme structure. These findings indicate that resistance in this aphid is mainly the result of insensistive AChE alteration, that the 3 mutations found might contribute to resistance, and that the AChEs encoded by both genes could serve as targets of insecticides.