MORTALITY OF Spodoptera frugiperda LARVAE FED WITH CORN LEAVES TREATED WITH AQUEOUS EXTRACTS FROM Azadirachta indica LEAVES

The objective of this study was to evaluate the effect of the feeding period on the mortality of Spodoptera frugiperda larvae, of different ages, fed with corn leaves treated with aqueous extracts from neem leaves. Two bioassays were carried out at Embrapa Milho e Sorgo, Sete Lagoas, MG, Brazil, under laboratory conditions. On the first one, neonate larvae were fed from one to six days with corn leaves parts treated with aqueous extract of neem leaves and after this feeding period the larvae were fed nontreated leaves. On the second bioassay, larvae of different ages (1 to 13 days) were fed corn leaves treated with the same exctract during the whole larval cycle. The extract was prepared with dry ground leaves of neem (150 g) placed in 1 L of distilled water. The data were submitted to the regression analysis. The results of the first bioassay showed that neonate larvae fed on corn leaves treated with neem extract for one day caused high larval mortality (99-100%) and prevented the insect from recovering its normal development after being transferred to non-treated leaves. Results of the second bioassy showed that larvae up to eight days old (3rd instar) reached high mortality (90%), which decreased considerably in larvae older than ten days