Effect of Temperature on the Infectivity of Entomopathogenic Nematodes against Shoot Borer (Conogethes punctiferalis Guen.) Infesting Ginger (Zingiber officinale Rosc.)

The attachment, penetration, infectivity and multiplication of eight native isolates of Entomopathogenic nematodes (EPNs), Heterorhabditis sp. (IISR-EPN 01), Steinernema sp. (IISR-EPN 02), Steinernema sp. (IISR-EPN 03), S. carpocapsae (IISR-EPN 06), Oscheius spp. (IISR-EPN 04, 05, and 08) and O. gingeri were tested against larvae of Conogethes punctiferalis at different temperatures viz., 20, 25, 30 and 35°C. The temperature significantly affected attachment, penetration, pathogenicity and multiplication ability of infective juveniles (IJs) of all tested EPNs. Among the test temperatures, maximum mortality of larvae was found at 30°C followed by 25°C, whereas the least mortality was recorded at 20 and 35°C. Maximum number of infective juveniles was multiplied at 30°C, however minimum multiplication was recorded at 35°C. Among the test EPNs, no multiplication of Heterorhabditis sp. (IISR-EPN 01), Steinernema sp. (IISR-EPN 03) and O. gingeri was recorded at 20°C. IJs attached to larvae of C. punctiferalis in higher number after 6 h at 25 and 30°C. Whereas, maximum number of IJs penetrated into C. punctiferalis larvae at 30°C. Therefore, the optimal temperature for infection and development for all promising EPNs was 30°C.