author(s)
Arun Janu, KK Dahiya and Pritish Jakhar

abstract
The study was conducted on whitefly in Bt cotton at Research Farm of Cotton Section, Department of Genetics and Plant Breeding, CCS Haryana Agricultural University, Hisar during kharif 2014 and 2015. The aim of this study was to quantify the whitefly dynamics on Bt cotton with prevailed weather conditions. To mitigate the loss due to whitefly attack and better yield, regression analysis of pest population and pertinent external climatic information is paramount. Regression analysis was carried out with SPSS software V19. In the present studies, R² was found with a range of 0.00 to 0.80 i.e. population of whitefly was influenced up to 80 per cent by the simple, multiple, stepwise and hierarchical linear regression models under Hisar conditions. Simple linear regression model during 2014 and 2015 revealed that morning relative humidity (RH_m) had a higher impact on incidence of whitefly. In the multiple linear regression model, the impact of weather factors on the whitefly in Bt cotton during 2014 exerted 64.90 per cent, 79.50 per cent during 2015 role in the whitefly population fluctuation. In stepwise linear regression model, only morning relative humidity (RH_m) exerted (37.70 and 28.90 per cent) the fluctuation of whitefly population during 2014 and 2015, respectively. Hierarchical linear regression models revealed that the impact on the fluctuation of whitefly population increases with the addition of the influence of weather parameters in both the years.