Prediction of aphid and jassid in rainfed Bt cotton using regression models based on abiotic factors

Mean peak population of aphid [Aphis gossypii (Glover)] and jassid [Amrasca biguttula biguttula (Ishida)] was recorded at 34 and 37 meteorological week, respectively coinciding with abiotic factors 30–32°C maximum temperature, 21–22°C minimum temperature and more than 70% mean relative humidity in rainfed Bt cotton. The population dynamics of pest reaches above ETL (Economical Threshold Level) or to lower and higher vital limit are associated with changing abiotic factors. Regression model (Y=137.79–0.38 (X1) + 1.37 (X2)-1.0 (X3) + 0.59 (X4)-0.74 (X5) + 0.67 (X6)-14.48 (X7)-1.35 (X8) + 2.14 (X9) for aphids and Y = 2.03–0.02 (X1) + 0.37 (X2) + 0.86 (X3) + 0.17 (X4) 0.05 (X5) + 0.28 (X6) + 0.59 (X7) + 2.31 (X8)-0.50 (X9) for jassids) based on abiotic factors for prediction of pest population in advance at least one week were developed to predict aphids and jassids population in Bt cotton. These models are beneficial for management of aphid and jassid incidence in Bt cotton.