Effect of Bacillus thuringiensis, Anagrapha falcifera multiple nucleopolyhedrovirus, and their mixture on three lepidopteran corn ear pests

The 1st step in developing microbials as alternatives to chemical insecticides is to determine susceptibility of insects and virulence of the microbials in the laboratory. Anagrapha falcifera multiple nucleopolyhedrovirus (AfMNPV) and 3 Bacillus thuringiensis products, HD-1-S-1980, XenTari, and Javelin, were bioassayed against neonate Ostrinia nubilalis (Hubner), Helicoverpa zea (Boddie), and Spodoptera frugiperda (J. E. Smith) by using a droplet feeding method. The virulence of the B. thuringiensis materials for H. zea and S. frugiperda was Javelin > XenTari > HD-1-S-1980 and for O. nubilalis it was Javelin > XenTari and HD-1-S-1980. AfMNPV was most virulent to H. zea, followed by S. frugiperda, and O. nubilalis. The effect of XenTari and AfMNPV mixtures on the mortality of the 3 corn ear pests also was examined. Mixtures of entomopathogens either had no effect on mortality when compared with both pathogens alone or mortality caused by the virus was reduced with the addition of B. thuringiensis.