Host Range, Pathogenicity and foraging Behaviour of Heterorhabditis indica, Steinernema asiaticum and Steinernema siamkayai Strains Indigenous to Haryana

Indigenous strains of Heterorhabditis indica, Steinernema asiaticum and S, siamkayai caused 100% mortality in Pieris brassicae (after 48h) and Agrotis ipsilon (after 24h), whereas it was 80, 10 and 40%, respectively in Helicoverpa armigera (after 48 h) in vitro. On Galleria mellonella, mortality by H. indica was 100% at 30°C, 6.6% at 25°C and 33.3% at 20°C after 48h, and It increased to 100% only after 120h of exposure. IJs from insects killed at 25°C could be recovered only after transferring to 20°C. Average yield of Us at 30, 25 and 20°C was 1.02x10⁵, 1.28x10⁵ and 1.51x10⁵ per insect larva, respectively. S. asiaticum resulted in 93.3% mortality at 25° and 30°, and 86.6% mortality at 20°C after 120h. Though emergence of IJs was delayed by 4 days at 30° and 20°C, the 1J yield per larva was not affected. S. siamkayai caused 100% mortality after 72h at all temperatures. In laboratory bioassays, both the Steinernema species revealed ambushing, whereas H. indica exhibited cruising behaviour.