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 (LC
50) 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 LC
50 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 LC
50 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.
