Abstract
The phytochemical azadirachtin from the neem tree Azadirachta indica was administered to different larval instars of the variegated cutworm, Peridroma saucia orally in artificial diet, topically, or by injection. Nutritional analyses revealed that insect growth inhibitory and antifeedant effects were independent of each other and relative to the level of treatment. Injection of a 2 μg/g body weight dose of azadirachtin to sixth-instar larvae does not lead to starvation. However, substantial developmental anomalies result upon pupation. Ligature experiments demonstrated that head ligation in last-instar larvae, counteracted the azadirachtin-induced interference with pupation, pointing to an “aza-sensitive head factor”. Exogenous application of juvenile hormones I or II or juvenile hormone esterase inhibitor, BEPAT (in order to elevate hormone levels in the larvae) did not counteract any of the effects of azadirachtin treatment. The significance of these results in terms of hormonal events in P. saucia is discussed.
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