Comparative virulence of using filter paper and leaf disc bioassay for entomopathogenic nematodes

Abstract

Entomopathogenic nematodes mainly symbiotic association with gram positive bacteria Xenorhabdus spp. and Photorhabdus spp. Entomopathogenic nematodes (EPNs) are beneficial nematodes parasiting insect pests and are being effectively used as a bio pesticide against a wide variety of insect pests. The present study was investigated the effect of using filter paper and leaf disc bioassay on the activity of the entomopathogenic nematodes, Heterorhabditis indica and Steinernema glaseri under laboratory conditions. The result showed that virulence of H. indica followed by S. glaseri was found to be more virulent to Spodoptera litura and Helicoverpa armigera. S. glaseri followed by H. indica were found to be more virulent to Agrotis ipsilon and Anomala communis based on LC50 and LD50 values in the filter paper method. In the leaf disc bioassay method found that S. litura larvae were found to be susceptible to H. indica and S. glaseri. The LC50 and LT50 of H. indica were significantly lower than that of S. glaseri. Compared to filter paper method, leaf disc bioassay requires lower LC50 of 7.01 IJ/larva and least LT50 of 21.22 h/larva to cause mortality to S. litura. The results concluded that mortality of insects recorded on leaf disc assay method was also lower when compared to filter paper exposure.