Combined effect of three insect growth regulators on the digestive enzymatic profiles of callosobruchus maculatus [coleoptera: bruchidae]

ABSTRACT

Insect growth regulators [IGRs] are insecticides that mimic insect produced hormones by regulating developmental process. They have little or no mammalian toxicity, and are considered reduced-risk insecticides that are often exempt from tolerance requirements of regulatory agencies. IGRs, especially, chlorfluazuron, hydroprene and hexaflumuron [benzoylphenylurea] are currently studied because of possibility of using in stored products protection. Many of IGRs compounds used in insect pests control are known to affect digestive enzymes. Chlorfluazuron, hydroprene and hexaflumuron were tested topically at doses of 0.25%, 0.5% and1% for chlorfluazuron and hydroprene and 0.5, 1 and 2microg/ml of hexaflumuron to investigate its effects on the activities of the digestive enzymes protease, amylase and lipase in Callosobruchusmaculatus larvae, which were affected by IGRs individually and in combination. When combined, the effect was more severe at low concentration. There were statistically significant differences [P enzyme activities in combined and individual treatments. Combination three IGRs caused a two-fold decrease in enzyme activity even at reduced concentration. Clear dose-response relationships were established with respect to enzyme activity. A synergistic effect of IGRs was found by combination of low doses. These effects are most pronounced in early instars