INFLUENCE OF NEEM OIL ON DETOXICATION ENZYME-ACTIVITY IN THE OBLIQUEBANDED LEAFROLLER, CHORISTONEURA-ROSACEANA

Larvae of the obliquebanded leafroller, Choristoneura rosaceana L. (Le pidoptera: Tortricidae), were fed artificial diet containing various d oses of neem oil. After 6 days of feeding, larvae (6th instar) were as sayed for activities of midgut esterases and glutathione transferases. Midgut protein contents were also determined, as were larval fresh an d dry weights. Some larvae were allowed to pupate and emerge as adults in order to determine enzyme activities, protein contents, and weight s (fresh and dry) of whole adult moths. Neem treatment did not affect the fresh weight of male larvae, although the highest neem dose (0.027 %, v/v) significantly reduced the fresh weight of females compared wit h controls. Dry weights followed the same pattern: no differences in m ales and reduced dry weight at the highest treatment dose in females. For adult moths, no differences in fresh weight were observed for eith er males or females. Dry weights were reduced at 0.008% neem in female s and 0.010% neem in males. Protein contents were reduced in a dose-de pendent manner in male and female larvae and in adult female moths. Fo r glutathione transferase activities, no significant differences were observed with either 3,4-dichloronitrobenzene or 1-chloro-2,4-dinitrob enzene as the test substrate. Although there were some significant dif ferences in rates of 1-chloro-2,4-dinitrobenzene conjugation in adult females, these differences were not dose-dependent. Esterase activitie s, measured with a-naphthyl acetate and cu-naphthyl butyrate as substr ates, were significantly reduced in adult moths (females and males) at all neem treatment doses. Larval esterase activities were similarly r educed at the 0.027% dose. These results indicate that neem oil affect s esterase activities but not glutathione transferase activities, and that these effects are most pronounced in adult moths that were expose d to neem as larvae. Neem may be useful in the management of insect po pulations where insecticide resistance has developed as a result of el evated esterase activity. (C) 1996 Academic Press.