Morphology of the Alimentary Canal of Spodoptera frugiperda (J E Smith) Larvae (Lepidoptera: Noctuidae) Fed on Neem-Treated Leaves

Research involving plants with insecticide activity evolved significantly in the last decades. Among these plants, the neem tree, Azadirachta indica, is commonly used against several insects, mainly Lepidoptera. The neem efficiency depends on the target insect and on the concentration used. A barrier against potential toxic agents ingested together with the food is the alimentary canal. Thus, this research aimed to describe the histology of the alimentary canal of Spodoptera frugiperda (J E Smith) larvae fed on leaves treated with neem (Neemseto (R)) at a concentration of 0.5% and 1.0% and non treated, at different intervals ( 48, 96, 144, 192 and 240h), by quantifying the regenerative cells and analyzing the secretion of the mesenteron histochemically. Larvae were immobilized at low temperatures (-4 degrees C), the alimentary canal was removed, fixed in Bouin's aqueous, embedded in paraplast and historesin, sectioned and stained with hematoxilin-eosin and periodic acid-Schiff. The histology of the alimentary canal of S. frugiperda was similar to other lepidopterans. Neem effects on morphology were seen only in the mesenteron, depending on the time and concentration used, such as: epithelium, reduction on regenerative cells and on the secretory activity in this region, confirmed by the histochemistry in both neem concentrations. These alterations were observed after 96h at 1.0%, and 144h at 0.5%. These results indicte that neem (Neemseto (R)), at the concentrations studied, may be effective to control S. frugiperda because it promotes meaningful morphological alterations in the mesenteron.