Prevalence of insecticide resistance and enhanced detoxifying enzymes in field populations of Tuta absoluta (Lepidoptera: Gelechiidae) in the major Tomato growing regions of South India.

Abstract

South American pinworm Tuta absoluta (Meyrick) is an invasive and major tomato pest that attained resistance or reduced susceptibility to most insecticides used in their management due to repeated and intensive applications. This study aimed to find the levels of resistance in T. absoluta populations collected from South Indian states against novel insecticides such as chlorantraniliprole 18.5% SC, flubendiamide 39.35% SC, spinosad 45% SC, indoxacarb 14.5% SC, and emamectin benzoate 5% SG using leaf dip bioassay. Among the eight populations collected from major tomato growing belts spanning three states of South India (Andhra Pradesh, Karnataka and Tamil Nadu), Krishnagiri of Tamil Nadu showed the highest level of resistance to flubendiamide and the least resistance was shown by the Tirupati population, with a resistance ratio of 174.89 and 2.24, respectively. Significant correlation was found between LC₅₀ values of flubendiamide and chlorantraniliprole (0.859), emamectin benzoate and flubendiamide (0.855) and spinosad and emamectin benzoate (0.866). The biochemical assay conducted to quantify the mixed function oxidase (MFO), carboxyl/choline esterase (CCE) and glutathione S-transferase (GST) in the T. absoluta larval populations showed an increased level of MFO, CCE and GST in Krishnagiri population with 15.59, 1.72 and 6.02-fold, respectively compared to susceptible population. It showed that the detoxification enzyme plays an important role in the insecticide resistance of the field population of T. absoluta. The results serve as an initial assessment for further understanding of the molecular mechanisms of insecticide resistance at the genetic level to design and implement successful insecticide resistance management strategies.