Changes of phenoloxidase activity in hemocytes of Helicoverpa armigera (Lepidoptera: Noctuidae) exposed to sub-lethal concentrations of insecticides

The cotton bollworm, Helicoverpa armigera (Hübner), is one of the most important pests of crops. Like other insects, this insect has an immune system against external threats such as various diseases, parasitoids, and chemical compounds. Phenoloxidase is a key factor in the immunity of insects and other arthropods. The present study investigated the lethal effects of four insecticides, indoxacarb, profenofos, chlorfluazuron, and hexaflumuron, and their effects on phenolic oxidase activity in cotton bollworm. Among the studied insecticides, in two bioassays (mixture of insecticide with artificial food and immersion of sugar beet leaves), Chlorfluazuron had the highest toxicity (LC50 = 1.71 and 3.11 mg ai/liter, respectively). Also, the highest phenol-oxidase activity at 24 h was for larvae treated with chlorfluazuron and hexaflumuron. Also, when treated with chlorfluazuron and hexaflumuron, the larvae fed on an artificial diet had higher phenoloxidase activity than those fed on sugar beet cultivars.