Latent Effects of Chitin Synthesis Inhibitor; Chlorfluazuron on The Fall Armyworm; Spodoptera frugiperda (Lepidoptera: Noctuidae)

Document Type : Original Article


Plant Protection Research Institute, Agriculture Research Center


The fourth larval instar of Spodoptera frugiperda was treated, for 24 h, with LC50 of chlorfluazuron as a chitin synthesis inhibitor (0.5027 ppm) to examine its latent effects after counting acute mortality and ecdysis to the 5th instar. Percentage mortality after 24, 48 and 72 h postecdysis was 2, 12 and 18% from the whole number of treated larvae. Larval weight and main metabolites were significantly decreased as compared to control larvae. This reduction increased over time, especially for lipids. The early depression of lipids suggested that the larvae suffered from malnutrition probably due to starvation and that digestion did not go properly. Treatment reduced proteases and amylase activity even after 72 h postecdysis but had no significant changes for β-glucosidase and lipase.  Starvation and the observed effect on digestive enzymes may lead to a decrease in body metabolites and consequently body weight, so it is suggested that larvae are no longer able to complete their development well and will be adversely affected.  It could be concluded that treatment of the fall armyworm larvae with chlorfluazuron led to lethal and sub-lethal latent effects more or less like that induced by the acute effects of the insecticide.  Latent effects, from the practical point of view, must be taken into consideration in pest management programs that aim to decrease insect population to decrease cost and toxic hazards.