Department of Botany, Andhra University, Visakhapatnam-530 003, Andhra Pradesh (India).
The feasibility of using Beauveria bassiana (Bals.) Vuill., an entomopathogenic fungus with a wide range, was explored in cotton pest management. This fungus proved virulent against Sylepta derogata Fabricius in laboratory bioassay tests. It was evaluated in the field. Two, one hectare plots 0.25 km away from each other naturally infested by the leaf roller were chosen. One was treated and the other served as the control. The plots were divided into 10 equal blocks. The intensity of the pest was estimated by counting the number of rolled leaves per plant in a sample of 10 plants per block. The fungus was cultured on finely crushed sorghum for 12 days. The heavily sporulated culture of the fungus along with the sorghum base equalling ˜2.7 x 10 spores was broadcast on the plants in each of the replicate blocks. The application proved effective. A week after treatment, mycotic larval cadavers were spotted on the plants and soil. Within three weeks, the plants were completely rid of the pest. The plants in the control blocks remained stunted due to the persistence of the pest in the field and drieh up 45 days earlier than those in the treated plot. The average yield of the treated blocks was 40 times more than the control blocks. The simple technology in developing the fungal inoculum and its field performance makes it an attractive candidate for inclusion in cotton pest management programmes.
