Field Evaluation of Biocontrol Agents for the Management of Major Insect Pests of Coleus

Abstract

A field experiment was laid at Agricultural College and Research Institute, Madurai during June – November 2009 to evaluate the efficacy of various bio-control agents individually and in different combinations for the management of major insect pests of coleus. Five releases of Chrysoperla carnea (50,000 eggs/ha) at monthly interval were effective in reducing the incidence of thrips (Scirtothrips dorsalis), recording the mean population of 8.2 nos./sq.cm with 60.0 per cent reduction over untreated check. Single release of C. carnea on 30 Days after Planting (DAP), Trichogramma chilonis on 60 DAP, single spray of Beauveria bassiana on 90 DAP and two rounds of spray of Bacillus thuringiensis on 120 and 150 DAP were effective against defoliator (Orphanostigma abruptalis), recording the lowest mean population of 2.6 nos./five plants with a reduction of 69.4 per cent over untreated check and the highest yield of 20,643 kg wet tubers/ha.