Effect of Weather Parameters on the Incidence of Thrips, Thrips tabaci Lindeman on Bt Cotton

The field experiments were conducted during kharif season of year 2014 & 2015 at Agricultural Research Station, Rajendranagar, Hyderabad, Telangana state, India to study the influence of weather parameters on the incidence of thrips population on Bt cotton. The results revealed that the peak incidence of thrips population was recorded on 35th Standard Week i.e., last week of August (32.87 thrips leaf–1) during kharif, 2014 and two peaks i.e., 35th Standard Week i.e., last week of August (33.93 thrips leaf–1) and 40th Standard Week i.e., the first week of October (40.40 thrips leaf–1) were recorded during kharif, 2015. Thereafter, its population declined gradually during both seasons. Correlations worked out between thrips population and weather parameters revealed that, one week (0.51*) and two weeks lag (0.65**) minimum temperature, one week lag (0.56**) morning relative humidity showed significant and positive influence, while one week lag (–0.44*) evaporation showed significant negative influence on thrips incidence. The prediction model developed for the thrips population revealed that the model explained the variation to an extent of 54 per cent in thrips incidence under the influence of minimum temperature and morning relative humidity.