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

Abstract

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.