INFLUENCE OF SOIL MOISTURE ON VIRULENCE OF HETERORHABDITIS INDICA AGAINST BRAHMINA CORIACEA (HOPE)

Abstract

Soil moisture has significant effects on the infectivity and persistence of entomopathogenic nematodes (EPN). The research work describe the impact of soil moisture on the virulence of Heterorhabditis indica Poinar against I-III instar grubs of B. coriacea. In the present study, H. indica was tested at three different soil moisture levels of 55, 60 and 65 per cent against B. coriacea. There was gradual decrease in LC50 values of H. indica with increase in soil moisture percentage in all instars of B. coriacea indicating positive impact of soil moisture on its virulence. The LC50 values against first instar grubs of B. coriacea were computed to be 303.55, 254.42 and 231.09 IJs/ml at 55, 60 and 65 per cent soil moisture, respectively. In second instar, the LC50 values of H. indica at different soil moisture levels were calculated to be 329.12, 307.41 and 268.98 IJs/ml, respectively. The LC90 values were computed to be 2332.77, 2159.39 and 1723.52 IJs/ml. Against third instar, the LC50 values were found to be 394.08, 361.10 and 312.91 IJs/ml, and LC90 values were computed to be 3136.46, 2619.32 and 2234.69 IJs/ml. It was observed that LC50 values of H. indica decreased with increase in soil moisture and the results of the study iterated the role of soil moisture in dispersal of entomopathogenic nematodes and host infection.