Effect of abiotic factors on seasonal incidence and bio-efficacy of some newer insecticides against whitefly (Bemisia tabaci G.) on tomato crop (Solanum lycopersicum L.) in West Bengal

Tomato (Solanum lycopersicum L.) crop is susceptible to various insect pests of which whitefly (Bemisia tabaci Genn.) is the most predominant. Whitefly population first appeared in the field during 48th standard metrological week (SMW) that is 0.15 per three leaves. After that the population progressively increased and reached its peak (4.5whitefly per 3 leaves) in the 7th meteorological week when average temperature, relative humidity and bright sunshine were 21.9 0C, 66.83% and 5.6 hrs respectively. Correlation studies between whitefly population and weather parameters revealed that whitefly population showed significant positive correlation with temperature maximum while significant negative correlation with relative humidity(maximum, minimum and average). Maximum population reduction was found in the insecticidal treatment Imidacloprid 30.5 SC @0.004% active ingredient concentration (90.62%) and Diafenthiuron 50 WP @ 0.05% active ingredient concentration (89.29%).These were followed by Dimethoate 30 EC @ 0.06%, Dinotefuran 20 SG @ 0.006%, Spinosad 45 SC @ 0.007%, Clothianidin 50 WDG @ 0.005% and Flonicamid 50 WG @ 0.015% active ingredient concentrations , which recorded (85.21, 78.03, 76.48, 71.00 and 68.46% reduction over control). In untreated control the maximum number of whiteflies recorded was 4.00 per 3 leaves.