Meisner, J., Div. of Toxicology, ARO, Volcani Center, Bet Dagan, Israel
Ascher, K.R.S., Div. of Toxicology, ARO, Volcani Center, Bet Dagan, Israel
Zur, M., Div. of Plant Introduction, ARO, Volcani Center, Bet Dagan, Israel

The residual effect of a dried methanolic extract of neem (Azadirachta indica A. Juss) seed kernels was investigated with larvae of the Egyptian cotton leafworm, Spodoptera littoralis (Boisd.), in field trials. Fodder beet was sprayed with 1% emulsions of the extract. The treated leaves were collected from the field 1, 3, 5 and 9 days after spraying and offered to the larvae for 48 h. Survival and mean weight of the larvae were recorded 2, 4, 6, 9 and 11 days from the start of exposure to the residues, and rate of pupation was calculated. The extract had a strong antifeedant effect and an intense insect growth-regulating (IGR) effect in field-treated leaves, especially with the 1- and 3-day-old residues. A positive correlation was found between the age of the residues and the mean percent of live larvae, larval weight and pupation rate of the larvae. © 1983, Springer Science + Business Media B.V.. All rights reserved.