Biocidal Efficacy of a New and Native Species of Entomopathogenic Nematode against Gram Pod Borer, Helicoverpa armigera (Hubner)

Efficacy of new and native species of entomopathogenic nematode (EPN), Heterorhabditis casmirica SKUAST-K 104 was evaluated against gram pod borer, Helicoverpa armigera in laboratory conditions. Larval mortality was directly proportional to size of nematode inoculum level as well as time period but inversely proportional to larval size. H. casmirica SKUAST-K 104 applied @ 50, 100, 150 and 200 IJs per 2nd instar larva resulted in pest mortality by 0.00, 8.33, 16.66, and 25.00 per cent, respectively at 24 hours and they were statistically significant (p ≤ 0.05) from each other. At 200 IJs inoculum level, 8.33, 16.66, 25.0, 41.66 and 50 per cent mortality of 5th instar larva was recorded at 24, 48, 72, 96 and 120 hours post inoculation, respectively. LC50 values was directly proportional to the size of larva but inversely proportional to time period. On the other hand, LT50 values was directly proportional to the size of larva but inversely proportional to size of nematode inoculum level. LC50 values calculated at 24 hours for 2nd, 3rd, 4th and 5th instar larvae was 256.88, 277.24, 326.25 and 384.25, respectively, whereas at 120 hours it was 126.11, 160.22, 184.36 and 219.14, respectively. Similarly, LT50 values calculated at inoculum level of 50 IJs per 2nd, 3rd, 4th and 5th instar larvae were 105.0, 113, 122 and 131 hours, respectively but at highest inoculum level of 200 IJs, it was 75, 89, 94 and 100 hours, respectively. Nematode multiplication rate within the host cadaver was directly proportional to the size of the host. Minimum and maximum number of IJs/ larva was 2.72 x 105 and 1.03 x 105, obtained from 2nd and 5th instar larva, respectively.