Analysis of Pyrethroid Resistance in Helicoverpa armigera in Pakistan
Mar 7, 2019
Resistance to seven pyrethroids was regularly monitored in field populations of Helicoverpa armigera in Pakistan during 1991 to 1997 using an IRAC leaf-dip method. From 1991 to 1993, resistance was moderate to cypermethrin and cyfluthrin, low to alphacypermethrin, zetacypermethrin and deltamethrin, and very low to lambdacyhalothrin and bifenthrin. In 1994, there was a heavy outbreak of H. armigera on cotton which prompted farmers to apply pesticides frequently, especially pyrethroids. Consequently, resistance to cypermethrin, cyfluthrin, alphacypermethrin and deltamethrin rose to high levels in subsequent years. Resistance to zetacypermethrin and lambdacyhalothrin remained low during 1994 and 1995, but also reached high levels during 1996 and 1997 following their increased usage. Bifenthrin resistance was low up to 1996, rising to moderate levels in 1997. The variable patterns of development of pyrethroid resistance in H. armigera may be due to the selection of different mechanisms of resistance to different degrees with particular pyrethroids. This diversity of mechanism selection provides a good opportunity for insect resistance management within the pyrethroid class of chemicals.