Abstract

                                The symbiotic bacteria associated with entomopathogenic nematodes can be exploited as potential bio control agents against insect pests. X. bovienii, the symbiotic bacterium of S. feltiae in combination with Bt in the inoculation method, resulted in cent per cent larval mortality of C. medinalis on 2.5 days after treatment. However in the sole application of X. bovienii even at the highest dosage level of 108 cells per ml it showed the lowest larval mortality of eight per cent. X. japonica the symbiotic bacterium of S. kushidai KKM strain in the inoculation method, at 108 cells per ml with Bt combination recorded complete larval mortality at 72 h after treatment. Whereas in the absence of Bt, it recorded only 3.13 per cent mortality at the same dosage level of 108 cells per ml. Hence, we speculate that the addition of Bt synergise the virulence of symbiotic bacteria on C. medinalis.

Key words : Efficacy, Xenorhabdus bovienii, Xenorhabdus japonica, Cnaphalocrocis medinalis