Sublethal concentrations of azadirachtin affect food intake, conversion efficiency and feeding behaviour of Spodoptera littoralis (Lepidoptera: Noctuidae)

Sublethal concentrations of azadirachtin incorporated into artificial diet and offered to third-instar larvae of Spodoptera littoralis (Boisduval) prolonged larval instars and reduced food intake. These effects were observed after the treated larvae had been transferred to plain diet; the reduced food intake was therefore a secondary antifeedant effect. Azadirachtin did not influence digestion efficiency but diminished the ability of the larvae to convert both ingested and digested nutrients into growth, particularly immediately after treatment. This effect declined with time once the treatment with azadirachtin had ceased. Growth was more severely reduced than food intake, and the reduction in growth also occurred during periods when food intake was not affected, possibly due to post-ingestive effects.