Effects of Pyriproxyfen on detoxifying and intermediary enzymes of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae)

The insect growth regulators (IGRs) are compounds that interfere with growth physiology, particularly ecdysis and have an effective control against agricultural insect pests. Sublethal concnetrations of an insect growth regulator, pyriproxyfen, were prepared after bracketing test and were treated on last larval instars of Ephestia kuehniella to find their effects on detoxifying enzymes and those involving in intermediary metabolism. Treated larvae by aceton as control and others treated by 5, 15 and 30 µg/ml of pyriproxyfen were randomly choose after 24 and 48 hours post-treatment for enzymatic analysis including general esterases, glutathione S-transferases, acid and alkaline phosphatases, alanine and apartate aminotransferases as well as lactate dehydrogenase. By using α- and β-naphtyl acetate as substrates, activities of general esterases increases along with increasing of pyriproxyfen concentrations in both time intervals. Similar results were obtained regarding GSTs by using CDNB and DCNB. The lowest and the highest acid and alkaline phosphatses activities were found in control and treated larvae by 30 µg/ml of pyriproxyfen. Similar results were observed in case of alanine- and aspartate aminotransferase as well as lactate dehydrogenase. These results demonstrate that higher concentrations of pyriproxyfen increased activities of detoxifying enzymes to decrease effect of pesticide on larval physiological processes but pyriproxyfen statistically intervene in activities of enzymes involved in intermediary metabolism of E. kuehniella.