Abstract

Xanthogaleruca luteola (Coleoptera: Chrysomelidae) is an aggressive defoliating pest on elms (Ulmus sp.) worldwide. We evaluated the antifeedant and insecticidal effects of ethanolic and aqueous extracts from Melia azedarach L. green fruits and leaves of Peumus boldus Molina, on X. luteola third instar larvae, the most harmful stage. Five doses of the extracts were applied to fresh elm leaves to determine antifeedant effect evaluating consumed foliar area at 24 h. Insecticidal activity was assessed through daily mortality for 14 d. For each extract an antifeedant index, relative to respective control, and mean lethal concentrations (LC50) were calculated. We found a direct relationship between concentration and both antifeedant and insecticidal effects for all extracts. A dose of 6.1% w/v of ethanolic extract of M. azedarach green fruits significantly inhibited larvae feeding behavior by 91% with a LC50 1.49% at day 8. On the other hand, 3.4% w/v of ethanolic extract of P. boldus inhibited larvae feeding behavior by 81% and LC50 at day 8 was 0.92% w/v. All extracts showed insecticidal effect on X. luteola larvae, and the highest mortalities observed were 79% and 71% with ethanolic and aqueous extracts of P. boldus, respectively. Antifeedant and insecticidal effects observed with M. azedarach green fruits and P. boldus leaf extracts on X. luteola third instar larvae, support the development of botanical insecticides from both tree species in order to contribute to its integrated management.