25 Haz 2025 Çarşamba
Biopotency of two native entomopathogenic nematodes against tomato fruit borer, Helicoverpa armigera (H.) (Lepidoptera: Noctuidae) under laboratory conditions
Abstract : Bioefficacy of two native isolates of entomopathogenic nematodes viz., Steinernema feltiae MN044869 and Heterorhabditis bacteriophora MK263023 was worked out in laboratory conditions against tomato fruit borer, Helicoverpa armigera. Inoculum level of 25, 50, 75 and 100 IJs/ larva were applied against each larval instar for a time interval of 24, 48, 72 and 96 hours. It was found that with increase in initial inoculum level and time interval, the overall mortality increased and peaked at inoculum level of 100 IJs and after time interval of 96 hours, which was recorded to be 91.66%, 75.00%, 66.66% and 66.66% against 2nd, 3rd, 4th and 5th instar larva respectively in case of Steinernema feltiae MN044869. In case of Heterorhabditis bacteriophora MK263023 mortality also peaked at inoculum level of 100 IJs/ larva at a time interval of 96 hours which was recorded to be 75.00%, 66.66%, 58.33% and 58.33% against 2nd, 3rd, 4th and 5th instar larva respectively. With increase in larval size the mortality decreased and was lowest against 5th instar larva at any inoculum level and time interval. LC50 value decreased with increase in time interval that means we need less concentration of nematodes to cause 50% mortality with increase in time interval. LT50 value decreased with increase in inoculum level that means with increase in inoculum level we need less time to kill 50% pest population. Both LC50 and LT50 values increased with increase in larval size.