Cotton genotypes morpho-physical factors affect resistance against Bemisia tabaci in relation to other sucking pests and its associated predators and parasitoids.

Abstract

Cotton strains having different hair length and density were evaluated for tolerance to Bemisia tabaci, Amrasca devastans and Thrips tabaci, and survival of predators and parasitoids. The seed treatment effect on the population of these insect pests and natural enemies were also studied. Population of B. tabaci was higher on the strain Cyto-46, having trichome density of 474±12.9 per cm 2 and hair length of 705±44.8 microns and minimum on strain Cyto-12/91, having trichome density of 1011±21.0 per cm 2 and hair length of 644±27.3 µ. However, A. devastans was significantly higher on strain Cyto-12/91 whereas, thrips remained significantly less on the same strain Cyto-12/91. the total number of predators were significantly higher on strains having >600 trichomes per cm 2 whereas the level of parasitism remained the same on all the strains. Seed treatment proved effective against A. devastans only. However, the number of predators and percent parasitism was not significantly affected by the seed treatment. Present study revealed that the early season sucking pest complex can be managed by choosing the variety having moderate leaf hair density and if variety choice is limited then the early season sucking pest especially jassid could be managed effectively by the seed treatment.