Emamectin benzoate resistance in diamondback moth in different locations of Karnataka

Diamondback moth (Plutella xylostella L.) is one of the few insect species that has developed field resistance to all major classes of insecticides. In this view, the present investigation was carried out to study the levels of insecticidal resistance in the larvae of diamondback moth collected from major cabbage growing districts of Karnataka at Department of Agricultural Entomology, College of Agriculture, UAS, and Raichur during 2017-19. Log dose probit analysis indicated LC50 of emamectin benzoate in the range of 4.01 ppm to 31.77 ppm with maximum in Mysuru strain (39.07 ppm) and minimum (9.16 ppm) was reported from Raichur. The relative resistance ratio was found to be highest in the diamondback moth population of Mysuru (7.98-fold) followed by Haveri (7.02-fold), Chamrajnagar (6.84-fold), Bengaluru (5.69-fold), Chikmagalur (5.03 -fold) and Bidar (4.02-fold) over the susceptible Raichur strain. These results indicated that diamondback moth under selection pressure of emamectin benzoate showed higher degree of resistance.