Virulence of entomopathogenic nematodes against castor capsule borer Conogethes punctiferalis (Guenée)

Abstract

Two EPN species, Heterorhabditis indica Poinar and H. bacteriophora Poinar were evaluated for their virulence and reproductive potential against late instar larvae of castor capsule borer Conogethes punctiferalis (Guenee) with wax moth Galleria mellonella (L.) used for comparison. Late instar larvae were found highly susceptible at all six infective juvenile (IJ) concentrations (30, 60, 90, 120, 150 and 200 IJ larva−1) of both the EPNs evaluated. At 48 hr post infection, complete larval mortality was observed in both capsule borer and wax moth. LC50 values of 570 and 40.1 IJ larva−1 for capsule borer and 15.1 and 5.4 IJ larva−1 forwax moth were observed with H. bacteriophora and H. indica, respectively at 24 hr exposure. These values indicated the highly virulent nature of the EPNs. In capsule borer, maximum IJ production/cadaver for H. bacteriophora and H. indica was 84 ± 4.6 x 103 IJs larva−1 and 98 ± 6.7 x 103 IJs larva−1 at an inoculation concentration of 30 IJs larva−1. In wax moth, it was 262.3 ± 27.2 x 103 IJs larva−1 and 231.9 ± 8.1 x 103 IJs larva−1 for H. bacteriophora and H. indica, at an inoculation concentration of 90 IJs larva−1. These results reveal that host size is very important in fixing optimal inoculation concentration and final IJ production, and that both the EPNs have good potential for the management of capsule borer in castor.