Department of Entomology and Nematology P. O. Box 110620, University of Florida Gainesville, FL 32611, USA.
Midgut microsomes prepared from larvae of the fall armyworm, Spodoptera frugiperda (J.E. Smith), contain three enzyme systems which metabolize juvenile hormome III, namely, epoxide hydrolase, oxidase and esterase. The oxidase is membrane bound, requires NADPH for activity and is inhibited by carbon monoxide and piperonyl butoxide and therefore is a typical microsomal monooxygenase. Feeding the allelochemicals, indole-3-carbinol and ß-naphthoflavone, to the larvae caused 188% and 105% increases, respectively, in the JH III oxidase activity as compared with the controls. Induction of microsomal ecdysone 20-monooxygenase by allelochemicals was also studied in this insect. Dietary terpenoids [e.g., (+)- -pinene, (-)-menthol, l-menthone, (+)-pulegone, beta-myrcene, farnesol, nerolidol], indoles (e.g., indole-3-carbinol, indole-3-acetonitrile, harmine), flavonoids (e.g., flavone, beta-naphthoflavone), coumarins (e.g., xanthotoxin, coumarin), methylenedioxyphenyl compounds (e.g., safrole, isosafrole, myristicin), and ketohydrocarbons (e.g., 2-tridecanone) all stimulated ecdysone 20-monooxygenase activity in the larvae from 28 to 234% as compared with the controls. Harmine was the most potent inducer among those tested. Azadirachtin when administered orally or by injection had no effect on the 20-monooxygenase activity in fall armyworms.