Effect of temperature on survival of Steinernema seemae, S. masoodi and S. carpocapsae (Rhabditida: Steinernematidae) and their subsequent infectivity to prepupa of Helicoverpa armigera (Hu¨ bner)

Abstract

The survival and infectivity of three indigenous entomopathogenic nematodes, Steinernema seemae, S. masoodi and S. carpocapsae at different temperatures (15, 20, 25, 30, 35, 40 and 458C) were studied against prepupa of Helicoverpa armigera (Hu¨ bner). Percent survival of nematodes decreased with increases in temperature. However, 46.6% of the populations were able to survive and tolerate the sublethal temperature (458C) treatment for 6 h. Out of the populations that survived, 43.3% infectivity was observed against H. armigera prepupa. The survivors did not infect at 25 and 308C, rather their activity was found optimum. These heat tolerant isolates could play a vital role in the management of susceptible stages of H. armigera at high temperature regimes and for the management of other insect pests of agricultural importance, which pupate in the soil.