Assessing Toxicity and Histopathological Effects of a Novel Group Acetyl-CoA Carboxylase Insecticides (Tetramic and Tetronic Acids-Based) Against Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae)

In a laboratory study, this research focused on the effects of the insecticides spirodiclofen, spiromesifen, and spirotetramat, which are Acetyl-CoA carboxylase (ACC) inhibitors, on the mortality rates of Pectinophora gossypiella neonates. A comparative assessment of toxicity through contact and ingestion was conducted at 6, 12, 24, 48, and 72 hours. Results indicated that spirotetramat exhibited higher toxicity as the median lethal concentration (LC50) values significantly decreased over time (21.619 to 6.872 µg/ml). While spirodiclofen demonstrated moderate effectiveness, otherwise spiromesifen was considerably weaker, especially during the initial hours. Biological evaluation revealed prolonged larval developmental time and reduced weight in the treated larvae, with spirodiclofen causing the most significant effect. The highest mortality rate was observed for the spiromesifen treatment (81.7%), closely followed by spirodiclofen and spirotetramat (85.7% and 84.7%, respectively). There was a notable decrease in the pupation percentage and a significant increase in the pupal malformation percentage across all treatments compared to the control group. Histopathological examination revealed significant alterations in integument and gut structures, including degeneration of cuticle layers and destruction of epithelial tissues. These results highlight the potential utility of spirodiclofen, spiromesifen, and spirotetramat in integrated pest management for controlling P. gossypiella.