Insecticide Resistance in Helicoverpa armigera (Hubner) to Certain Commonly Used Insecticides
The results of discriminatory dose monitoring of resistance to commonly used insecticides like cypermethrin, monocrotophos, quinalphos and endosulfan during 1999–2001 at Varanasi and Mirzapur revealed that resistance to cypermethrin in Helicoverpa armigera larvae varied considerably between and within years of study at Varanasi and Mirzapur. The regions experienced high levels of resistance (44.8 to 87.8%) against cypermethrin 0.1 ?g throughout the experimental period and moderate levels (14.0 to 83.1%) against cypermethrin 1 ?g dose except during October-November in early pigeonpea collection of both the years. Moderate levels of resistance to quinalphos (7.2 to 82.7%) and monocrotophos(9.7 to 81.8%) were recorded while resistance to endosulfan remained at low to moderate level(l 1.4 to 56.2%) throughout the experimental period. The interaction between per cent resistance and place X period; place X treatment; place X period X treatment was found to be non significant. In other words, irrespective of place, insecticide input and period, the mean per cent resistance at both the places remain almost similar. While the interaction between per cent resistance and period X treatment was significant suggesting that there is a significant variation in per cent resistance among different months at both the locations during the period of experiment. Studies on insecticide input indicated that at Varanasi, organophosphates were the dominant group of insecticides followed by organochlorine compounds and very few farmers applied synthetic pyrethroids to control H. armigera on chickpea and pigeonpea.