Toxicity of the two insect growth regulators, pyriproxyfen and Lufox® against cotton bollworm

Abstract

This study investigated the field effects of two insect growth regulators, pyriproxyfen and lufenuron+fenoxycarb (A commercial combination), on some biological and physiological characteristics of third instar larvae of the cotton bollworm, Helicoverpa armigera Hubner. The insecticides significantly affected the weight and duration of larval and pupal development, the longevity of males and females, the egg laying and hatching rates. The larvae treated with sublethal concentrations showed an increase in the total number of hemocytes, plasmatocytes and granulocytes. A significant increase in aminotransferase activity was also observed in the hemolymph of treated larvae. The increased activity of acid phosphatase and alkaline phosphatase was also observed in the treated H. armigera larvae. The total activity of esterase and glutathione S-transferase as detoxifying enzymes also increased significantly after pyriproxyfen and lufenuron+fenoxycarb treatments compared to control. In contrast, the amount of storage macromolecules, protein, triglycerides and glycogen, which are related to the energy cost of pesticide treatment, decreased in the treated larvae compared to the control. According to the results of the present research, the pesticides pyriproxyfen and lufox can be used to control the population of H. armigera by interfering with the intermediate metabolism and cellular immunity of the larvae, but their efficiency and compatibility should be considered with other control methods, especially biological factors.