Regional monitoring of insecticide resistance in brinjal fruit and shoot borer (Leucinodes orbonalis Guenée): A study of indoxacarb, spinosad and thiodicarb in Odisha

The brinjal fruit and shoot borer (Leucinodes orbonalis) represents a significant pest of Solanum melongena (brinjal), adversely affecting its productivity. Current management approaches rely heavily on chemical insecticides, a dependency that has facilitated the development of resistance in various regions. A study conducted between November 2021 and September 2022 utilized a topical bioassay method to assess resistance trends in populations collected from four districts in Odisha against the insecticides Indoxacarb, Spinosad, and Thiodicarb. The results indicated a progressive increase in resistance to Indoxacarb until May 2022, as evidenced by LD?? values ranging from 0.525 to 0.752 µg/µl across districts. Subsequently, a decline in LD?? values was observed, potentially attributable to population turnover or a reduction in selection pressure. These trends were reflected in the resistance ratio (RR??), which peaked in May 2022 and declined by September. Among the districts, the Bargarh population exhibited the highest resistance to Thiodicarb, with a 42.39-fold RR??, underscoring localized resistance evolution. This study highlights significant heterogeneity in susceptibility across regions, emphasizing the urgent need for a revision of current pest management practices. It advocates for the judicious use of novel insecticides and adjustments in the application rates of established chemicals like Thiodicarb. Such measures are essential to mitigate resistance development and ensure the sustained productivity of Solanum melongena.