Evaluate the Susceptibility of Helicoverpa armigera against Helicoverpa armigera Nuclear Polyhedrosis Virus under Laboratory Conditions

Abstract

Helicoverpa armigera is a major polyphagous pest that can cause substantial crop losses. This laboratory study evaluated the susceptibility of H. armigera larvae to Helicoverpa armigera nuclear polyhedrosis virus (Ha-NPV) and examined the effects of host food and virus concentration on larval mortality and polyhedral inclusion body (PIB) yield. Third-instar larvae were maintained at 25 ± 2°C, 75 ± 5% RH, and a 14:10 h (L:D) photoperiod. For host-food evaluation, larvae received Ha-NPV at 1.66 × 10⁶ PIBs/larva through chickpea leaves, soaked chickpea grains, chickpea flour, or wheat flour. In 2019–20, mortality was highest with wheat flour (90.00%), followed by chickpea leaves (88.00%) and chickpea seed (86.00%), and lowest with chickpea flour (72.0%). Corresponding values in 2020–21 were 92.00%, 90.00%, 86.00%, and 72.0%, respectively. The highest PIB yields were recorded with wheat flour, reaching 2.21 × 10⁹ PIBs/larva in 2019–20 and 2.15 × 10⁹ PIBs/larva in 2020–21. Across virus doses from 1.66 × 10⁶ to 1.00 × 10⁷ PIBs/larva, cumulative mortality increased with concentration. Mortality ranged from 60.83% to 92.33% in 2019–20 and from 60.50% to 92.50% in 2020–21. The findings indicate that Ha-NPV pathogenicity under laboratory conditions varies with host food and dose, supporting further evaluation of this biocontrol agent for integrated management of H. armigera.