Effects of native entomopathogenic fungal strains and neem extract on Spodoptera frugiperda on maize.
The objective of this study was to evaluate the insecticidal activity of native entomopathogenic fungi and neem extract on Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) attacking maize (Zea mays L.). The treatments were the following: Metarhizium robertsii J.F. Bisch., Rehner & Humber and Fusarium solani (Mart.) Sacc at 1 × 108 spores ml-1 and 15% vegetable oil, neem extract in two combinations of 4% mass per volume, commercial insecticide, and a control without application. Response variables were incidence of S. frugiperda, severity of leaf damage, and grain yield. M. robertsii was most effective because of low incidence of S. frugiperda and severity of leaf damage; as leaf damage increased, grain yield decreased. Therefore, a high severity by insect attack can significantly decrease grain yield. It was observed that during the autumn-winter cycle the S. frugiperda incidence was lower, compared to the spring-summer cycle. M. robertsii decreased S. frugiperda incidence in both cycles.