Role of chitin inhibitors in altering fitness parameters and reproductive success of Chilo partellus (Swinhoe) (Lepidoptera: Crambidae)

Insect growth regulators (IGRs) are a promising alternative for controlling herbivorous pests. The current study investigated the effects of lufenuron and pyriproxyfen (at concentrations of 0.02, 0.04, and 0.08 ml) on the developmental duration from larva to adult, larval and pupal survival rates, fitness characteristics (larval and pupal length and weight), and reproductive parameters (longevity, fecundity, and fertility) of Chilo partellus (Lepidoptera: Crambidae), a major pest of fodder and cultivated crops. The results indicated significant reductions in developmental duration, survival rates, and fitness traits at higher concentrations of both IGRs. Specifically, at the 0.08 ml concentration, lufenuron and pyriproxyfen drastically shortened the larval (9.33 ± 0.19 days) and pupal (6.33 ± 0.19 days) durations compared to the control (16.22 ± 0.62 and 11.56 ± 0.59 days, respectively). Larval survival rates declined to 52.44% and 55.78%, while pupal survival rates dropped to 44.67% and 48.89%, respectively, at this concentration. Fitness assessments revealed significant reductions in larval and pupal lengths and weights following lufenuron and pyriproxyfen treatments. Adult longevity was also substantially reduced, with males and females exposed to lufenuron surviving for only 3.22 ± 0.29 and 4.67 ± 0.19 days, respectively, while those treated with pyriproxyfen lived for 5.33 ± 0.19 and 6.00 ± 0.19 days, compared to control values of 8.78 ± 0.48 and 11.89 ± 0.40 days, respectively. Furthermore, fecundity and fertility were significantly reduced at the 0.08 ml concentration, with lufenuron having the most pronounced effect (fecundity: 290.67 ± 19.00 eggs; fertility: 39.67 ± 0.84%).