author(s)
Binu V

abstract
An experiment was conducted during Kharif 2018-19 at the Experimental farm, Department of Agril. Entomology, Vasantrao Naik Marathwada Krishi Vidyapeeth, Parbhani, inorder to study the effect of repeated use of various insecticides like Imidacloprid 17.8% SL, Fipronil 5% SC, Lambda cyhalothrin 5% EC, Spinosad 45% SC, Acephate 75% SP, Buprofezin 25% SC, Flonicamid 50% WG, Acetamiprid 20% SP, Profenofos 50% EC, Diafenthiuron 50%WP, Acephate 50% + Imidacloprid 1.8% SP, Pyriproxyfen 5% + Fenpropathrin 15% EC, Profenofos 40% + Cypermethrin 4% EC on the whitefly population infesting Bt cotton. The highest reduction in whitefly population was recorded in Diafenthiuron 50% WP after the first, third, fourth and fifth sprayings with mean populations of 0.30, 0.93, 10.50 and 6.69 /leaf, respectively. This was found to be statistically at par with Flonicamid 50% WG after first, second, third, fourth and fifth sprayings with population means of 0.45, 1.72, 1.14, 10.97 and 7.07/leaf, respectively. Due to repeated application, the whitefly population increased drastically in Fipronil 5% SC and Lambda cyhalothrin 5% EC after the third spraying. Also, Fipronil 5%SC and Lambda cyhalothrin 5% EC recorded maximum whitefly population of 44.68/leaf and 41.01/leaf, respectively after five sprayings.