Fluctuating temperature: A cause for survival and development of entomopathogenic nematodes, <em>Heterorhabditis indica</em> and <em>Steinernema carpocapsae</em>

Abstract

Entomopathogenic nematodes (EPN) belonging to the families of Steinernematidae and Heterorhabditidae are obligate pathogens of a wide range of insects. But their survival and efficacy is adversely affected by the temperature. Therefore, in the present study, we determined the survival ability of <em>Steinernema carpocapsae</em> (Weiser) and <em>Heterorhabditis indica</em> (Poinar) infective juveniles (IJ) by exposing them to various temperatures. Results showed that the percentage survival with the maximum exposure time (48 h) at 25 and 40°C, for <em>S. carpocapsae</em> was 100 and 32.93%, respectively. <em>H. indica</em> which also showed 100% survival after exposure to 25°C, did not survive at 40°C. Among the nematodes, <em>S. carpocapsae</em> showed more tolerance to high temperature compared to <em>H. indica</em> and exposure time also significantly different in both nematodes. When IJs used as inoculum source after exposing to various temperature levels, the percent penetration was reduced and, importantly, progeny production was very less on Greater wax moth larvae. On desiccation, IJs of both <em>S. carpocapsae</em> and <em>H. indica</em> showed significant survivalability. <em>H. indica</em> IJs showed significantly more survival compared to <em>S. carpocapsae</em> when exposed to different desiccating levels.