Behavioural responses of locusts and Spodoptera littoralis to azadirachtin and azadirachtin analogues containing fluorescent and immunogenic reporter groups

Analogues of azadirachtin labelled with fluorescent and immunogenic reporter groups were assessed for antifeedant activity against Locusta migratoria, Schistocerca gregaria and Spodoptera littoralis. The results of the choice and no-choice feeding bioassays showed that the azadirachtin analogue labelled with dinitrophenylamino (DNP-azadirachtin) was the most potent of the 5 analogues tested. The behavioural responses of L. migratoria to this analogue did not differ significantly from those to azadirachtin. Azadirachtin analogues labelled with dansyl showed potent antifeedant activity, whereas the biotin labelled analogue was inactive. Electrophysiological studies undertaken on the maxillary styloconic sensilla of S. littoralis showed that the dansyl and DNP analogues stimulated neurones in both the medial and lateral sensilla. The neural input from these neurones correlated positively with the antifeedant activity of azadirachtin and the analogues.