Insecticide induced resurgence of Scirtothrips dorsalis Hood: Role of biochemical changes in chilli and natural enemies suppression

The improper use of insecticides poses risks to both human health and the environment, leading to issues such as insecticide residue, resistance, resurgence and increased management costs. The chilli thrips, S. dorsalis Hood (Thysanoptera: Thripidae) is a significant insect pest infesting vegetable crops and its management has become increasingly challenging due to its resurgence in response to commonly applied insecticides. A field experiment was conducted at UAS, Raichur, India, during the Kharif season of 2020 and the summer of 2021 to assess the effects of insecticides on the resurgence of S. dorsalis. The results demonstrated significant resurgence activity following the insecticide application. Fipronil, fenpropathrin and lambda-cyhalothrin led to high resurgence rates and a reduction in the populations of natural enemies of thrips. Subsequent treatments after the resurgence showed a decrease in defensive biochemicals such as flavonoids, tannins and phenols, while levels of total sugars, proteins and proline increased. Path coefficient analysis revealed a strong positive correlation between the insecticides and the increase in total sugars, proteins and proline, while negatively affecting flavonoids, tannins and phenols. The resurgence of S. dorsalis was closely associated with changes in plant biochemistry following insecticide application and the reduction of natural enemy populations.