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Desensitization of fifth instar Spodoptera litura to azadirachtin and neem
Author(s) -
Bomford Michael K.,
Isman Murray B.
Publication year - 1996
Publication title -
entomologia experimentalis et applicata
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.765
H-Index - 83
eISSN - 1570-7458
pISSN - 0013-8703
DOI - 10.1046/j.1570-7458.1996.00101.x
Subject(s) - azadirachtin , spodoptera litura , instar , biology , meliaceae , capitata , larva , toxicology , botany , horticulture , pest analysis , zoology , brassica oleracea , agronomy , pesticide
The deterrence of azadirachtin, in its pure form and as a constituent of neem seed extract, to fifth instar Spodoptera litura (Fab.) larvae, was measured using cabbage, Brassica oleraceae (L.) var. capitata, leaf disc assays. Paired‐choice assays, in which larvae could choose between feeding on a treated (1.3 ng azadirachtin per square cm leaf area) or an untreated leaf disc for 2 h, were conducted at 24 h intervals throughout the fifth instar. In addition, no‐choice assays, in which larvae could feed on only one leaf disc (10 ng azadirachtin per square cm leaf area) for 1.5 h, were conducted consecutively over a six hour period at the beginning of the fifth instar. The effects of hunger and habituation on desensitization in our no‐choice tests were partitioned. After repeated exposures, larvae became desensitized to pure azadirachtinal in both choice and no‐choice tests, but did not desensitize to neem containing the same absolute amount of azadirachtin in choice tests. Hunger was responsible for approximately one third of the desensitization response in the no‐choice tests. Sensitivity to azadirachtin was independent of age within the fifth instar.