Effect of sunlight on azadirachtin: Antifeeding potency

Abstract

Abstract Exposure of azadirachtin to sunlight caused a rapid decrease in antifeeding potency against newly emerged first instar (0.046 mg) fall armyworm, Spodoptera frugiperda (J. E. Smith), as compared to unexposed azadirachtin. Acetone solutions of azadirachtin exposed for seven days gave more than a 50 percent reduction in activity while azadirachtin exposed for sixteen days gave complete reduction in activity with destruction of the compound. p‐Aminobenzoic acid, a uv‐absorbing additive, gave slight protection to azadirachtin from photodegradation. Azadirachtin, mixed with various plant oils, was exposed to sunlight for two weeks. Bioassay of these mixtures showed that neem, angelica, castor, and calamus oils provided moderate protection (<25 percent) to azadirachtin from degradation by sunlight.