Institute of Zoology, University of the Punjab, Lahore, Pakistan.
Ecotoxicology. 2024 Mar;33(2):226-234. doi: 10.1007/s10646-024-02742-2. Epub 2024 Feb 29.
The use of insecticides in agricultural settings often exerts negative effects on nontarget species. Methomyl, a broad-spectrum carbamate insecticide, is recommended to manage a number of insect pests of the cotton crop. Recently, Musca domestica, which is a nontarget insect species in cotton fields, has shown resistance to methomyl in Pakistan. The present study tried to assess resistance-risk assessment, rapidity of resistance development to methomyl, cross-resistance potential to other insecticides, resistance heritability and to forecast the projected rate of resistance development under field conditions. For this purpose, a field strain of M. domestica with 186 fold resistance to methomyl was re-selected in the laboratory for eight consecutive generations. Consequently, LD values increased rapidly (126.64 ng/fly to 3112.79 ng/fly) compared to those before selection experiments. Similarly, RR values increased from 186 to 3113 fold as a result of the selection process. However, resistance to methomyl did not remain stable when the selected strain (Meth-SEL) reared for the next five generations in a pesticide free environment. The Meth-SEL strain also developed cross-resistance to permethrin. The realized heritability (h) value for the Meth-SEL strain was 0.39 with 27% average mortality of M. domestica. Assuming the standard deviation (σp) value 0.27 and the h value 0.39 for eight generations of continuous exposure to methomyl, then five, seven, eight, ten and twelve generations at 90, 80, 70, 60 and 50% selection intensity, respectively, would be required for a tenfold increase in the LD value of methomyl. In conclusion, the Meth-SEL strain of M. domestica exhibited a high risk of resistance development to methomyl under continuous selection pressure. Resistance increased rapidly during selection experiments that reflect the probability of resistance development under field conditions if M. domestica receive exposures to methomyl during its applications for the management of target pest species.
在农业环境中使用杀虫剂通常会对非靶标物种产生负面影响。灭多威是一种广谱氨基甲酸酯类杀虫剂，被推荐用于防治棉花作物的多种害虫。最近，在巴基斯坦，棉田中的非靶标昆虫家蝇对灭多威表现出了抗性。本研究试图评估抗药性风险评估、对灭多威快速发展的抗性、对其他杀虫剂的交叉抗性潜力、抗性遗传力，并预测在田间条件下抗性发展的预计速度。为此，在实验室中连续 8 代对具有 186 倍抗药性的家蝇田间种群进行了重新选择。结果，LD 值迅速增加（从 126.64ng/只增加到 3112.79ng/只），与选择实验前相比有所增加。同样，由于选择过程，RR 值从 186 增加到 3113 倍。然而，当选择的菌株（Meth-SEL）在无农药环境中连续饲养 5 代时，对灭多威的抗性并不稳定。Meth-SEL 菌株对氯菊酯也产生了交叉抗性。Meth-SEL 菌株的实际遗传力（h）值为 0.39，家蝇的平均死亡率为 27%。假设标准偏差（σp）值为 0.27，h 值为 0.39，连续暴露于灭多威 8 代，那么在 90%、80%、70%、60%和 50%的选择强度下，分别需要 5、7、8、10 和 12 代，才能使灭多威的 LD 值增加 10 倍。总之，在连续选择压力下，Meth-SEL 菌株的家蝇对灭多威表现出了很高的抗药性发展风险。在选择实验中，抗性迅速增加，反映了如果家蝇在应用过程中接触到灭多威，那么在田间条件下抗药性发展的可能性。
