Effects of Pyriproxyfen on Intermediary Metabolism of Rice Striped Stem Borer, Chilo suppressalis Walker (Lepidoptera: Crambidae)

Effects of Pyriproxyfen were determined on intermediary metabolism in the fifth larval instars of Chilo suppressalis via assessments of various enzymatic and non-enzymatic compounds. Bioassay of larvae revealed LC_10–50 values of 18, 72 and 190 µg/ml of pyriproxyfen. Results on alanine aminotransferase revealed lower activities in treated larvae versus control for all time intervals while activity of aspartate aminotransferase showed higher activities in treated larvae by 18 and 72 µg/ml of pyriproxyfen. Activities of γ-Glutamyl transferase and aldolase in treated larvae were significantly higher than those of control larvae. Treating of larvae by different concentrations of pyriproxyfen significantly increased lactate dehydrogenase activity for all time intervals although activity of the enzyme after 1 h was not significantly different among control and treated larvae. Activities of acid and alkaline phosphatases in treated larvae were higher than those of control. Amount of high and low density lipoproteins in treated larvae was higher than those of control except for time interval of 3 h of HDL in which control larvae revealed higher amount than 72 and 190 µg/ml treated larvae. Increased activity of the enzyme was noticed in treated larvae versus control in case of general esterases. Similar results were observed in case of glutathione S-transferase. Amount of triacylglyceride, glycogen and protein in control larvae was higher than those of treated larvae for all time intervals indicating their depletion due to energetic costs of pyriproxyfen treatment. These results clearly indicated negative effects of pyriproxyfen on intermediary metabolism of larvae that might lead to desirable mortality in pest population.