Holderman Chris J, Swale Daniel R, Bloomquist Jeffery R, Kaufman Phillip E
Entomology and Nematology Department, University of Florida, Gainesville, FL 32611, USA.
Department of Entomology, Louisiana State University Agricultural Center, Baton Rouge, LA 70803, USA.
Insects. 2018 Jun 12;9(2):63. doi: 10.3390/insects9020063.
Horn flies, , a major cattle pest in the USA, cause substantial economic losses and current control methods rely heavily on insecticides. Three horn fly populations were evaluated for insecticide susceptibility to permethrin, β-cyfluthrin, and diazinon. Susceptibility was variable by population, with the greatest resistance exhibited by a 66-fold resistance ratio (RR) to permethrin and >14-fold RR to diazinon. Mechanisms of resistance were determined using molecular techniques and enzymatic assays. The knockdown resistance () genotype (L150F) associated with pyrethroid resistance, and a G262A mutation in acetylcholinesterase, previously associated with organophosphate resistance, were found in all field populations evaluated. Insensitivity of diazoxon at the acetylcholinesterase (AChE) target site was significantly different in horn flies from one of the field sites. For metabolic detoxifying enzymes, cytochrome P450 nor general esterases showed a significant difference between field strains and a laboratory susceptible strain. Pyrethroid resistance was likely due to the presence of the L150F mutation in the population. In vitro studies targeting the AChE enzyme did not support the notion that the G262A mutation was the sole cause of resistance to organophosphates, and, therefore, the exact resistance mechanism to diazinon was not able to be confirmed.
角蝇是美国牛群的主要害虫，会造成巨大的经济损失，目前的防治方法严重依赖杀虫剂。评估了三个角蝇种群对氯菊酯、β-氯氟氰菊酯和二嗪农的杀虫剂敏感性。不同种群的敏感性存在差异，其中一个种群对氯菊酯表现出最大抗性，抗性比（RR）为66倍，对二嗪农的RR>14倍。使用分子技术和酶促测定法确定抗性机制。在所有评估的野外种群中都发现了与拟除虫菊酯抗性相关的击倒抗性（）基因型（L150F），以及先前与有机磷抗性相关的乙酰胆碱酯酶中的G262A突变。来自其中一个野外地点的角蝇中，二嗪磷在乙酰胆碱酯酶（AChE）靶位点的不敏感性存在显著差异。对于代谢解毒酶，细胞色素P450和一般酯酶在野外菌株和实验室敏感菌株之间没有显示出显著差异。拟除虫菊酯抗性可能是由于种群中存在L150F突变。针对AChE酶的体外研究不支持G262A突变是对有机磷抗性的唯一原因这一观点，因此，无法确定对二嗪农的确切抗性机制。
