Resistance profiling of Phthorimaea absoluta (Meyrick) from tomato fields of Belagavi, Karnataka

Abstract

South American tomato pinworm, Phthorimaea absoluta (Meyrick), poses a major threat to tomato production in India, with insecticide resistance becoming a key challenge for its effective management. The present study assessed the resistance status of P. absoluta and surveyed insecticide use patterns in tomato fields of Belagavi district, Karnataka. Field populations were collected and leaf dip bioassays were conducted using eight insecticides. Probit analysis revealed moderate resistance to chlorantraniliprole, with an LC50 of 60.631 ppm and a resistance ratio of 19.24 fold compared to the susceptible strain. While, lambda-cyhalothrin (LC50: 56.294 ppm; RR: 7.36), profenofos (LC50: 1350.221 ppm; RR: 7.35) and emamectin benzoate (LC50: 46.821 ppm; RR: 6.83) showed low levels of resistance. However, cyantraniliprole (LC50: 39.987 ppm; RR: 6.65), flubendiamide (LC50: 32.378 ppm; RR: 4.96), spinosad (LC50: 27.107 ppm; RR: 5.44) and indoxacarb (LC50: 20.609 ppm; RR: 3.45) exhibited reduced susceptibility. However, wider LC50 – LC90 gaps indicated population heterogeneity and possible resistance build-up. The insecticide usage survey revealed indiscriminate use of chlorantraniliprole, adding selection pressure and cross resistance due to possible detoxifying enzymes activity.