Effect of Fipronil + Isoprothiolane against Onion Thrips and Purple Blotch Disease and Its Effect on Parasites and Predators

Abstract

Onion (Allium cepa L.) is one of the important vegetable cum condiment crop grown throughout the world. Onion crop is infested by various insect pests and diseases right from seedling to harvesting stage. The experiment was conducted in farmer’s fields of Ranebennur (Haveri–District) to evaluate the bio-efficacy and Phytotoxicity of Fipronil + Isoprothiolane against Thrips and Purple Blotch disease in onion and its effect on parasites and predators during kharif-2018 and rabi-2019 seasons. Amongst the treatments, the formulation Fipronil 5% + Isoprothiolane 28% EC @ 1500 ml/ha was excellent in controlling thrips (2.47/trifoliate leaf) and showed the least severity of purple blotch  (3.02% PDI) followed by Fipronil 5% + Isoprothiolane 28% EC@ 1250 ml/ha (2.85 and 3.25)1000 ml/ha (2.99 and 3.67 % PDI) respectively. The results revealed that amongst the treatments, Fipronil 5% + Isoprothiolane 28% EC @ 1500 ml recorded the highest bulb yield                (21.52 t/ha) which was on par with the 1250 and 1000 ml/ha. The formulation Fipronil 5% + Isoprothiolane 28% EC @ 1000 ml/ha was found to be  cost effective followed by treatment of Fipronil 5% + Isoprothiolane 28% EC @ 1250ml /ha for control of thrips and  prevention of Purple Blotch disease hence which is recommended for  control of thrips and Purple Blotch  disease in onion.