Seasonal Monitoring of Insecticide Resistance in Helicoverpa armigera on Cotton and Chickpea

Data on pest-resistance to each insecticide (cypermethrin, endosulfan, quinalphos, methomyl and spinosad) using discriminatory doses were recorded for cotton-chickpea growing season during 2005–06 and 2006–07. Resistance frequencies were higher for cypermethrin (0.1 ug) throughout the study period. The resistance against cypermethrin was minimum in fourth week of January (72.2 per cent) and highest during October first week and August third week (92.2 per cent). Endosulfan resistance in Helicoverpa was low to moderate and was found maximum in the last week of September (47.8 per cent), and minimum (7.8 per cent) in the first week of October. Resistance to methomyl (0.1 ug/ul) & quinalphos (0.75ug/ul) was low to moderate. The pooled mean resistance to methomyl was minimum in fourth week of August (7.8 per cent) and maximum in third week of October (55.6 per cent). However, the mean resistance to quinalphos ranged from 10.0 to 55.6 per cent. Resistance to cypermethrin (0.1ug/ul), was moderate to high, while in quinalphos, methomyl and endosulfan it was low to moderate. Resistance to spinosad (1.0 ug/ul) was low (1.1 to 20 per cent) throughout the study period of 2005–06 and 2006–07 respectively.