Ecological determinants of mortality in Helicoverpa armigera infesting tuberose in the Marathwada region of Maharashtra

AbstractA field investigation was conducted to evaluate the ecological determinants of mortality in Helicoverpa armigera (Lepidoptera: Noctuidae) infesting tuberose, Agave amica (Medikus) Thiede & Govaerts. Mortality was quantified across early-instar, late-instar, and pupal stages during two successive generations. In the first generation, early-instar mortality occurred due to unknown factors (15.86%) and parasitism by Aleiodes sp. (4.71%). Late-instar mortality was caused by unknown factors (14.84%) and infection by Helicoverpa armigera nucleopolyhedrovirus (HaNPV) (11.61%), while pupal mortality reached 39.45%, primarily due to unidentified causes. The generation exhibited a survival rate of 0.37 with a cumulative K value of 0.7380, indicating a 73.80% population reduction. In the second generation, early-instar mortality resulted from unknown factors (18.52%) and Bacillus thuringiensis infection (11.36%), whereas late-instar mortality was caused by HaNPV (17.24%) and unknown factors (25.64%). Pupal mortality (20.83%) was mainly attributed to parasitism by tachinid flies. The generation survival rate was 0.35 with a cumulative K value of 0.7541, reflecting a 75.41% population reduction. Key factor (K) analysis revealed that pupal mortality was the dominant factor in the first generation, while late-instar mortality was most influential in the second. The findings emphasized the regulatory role of natural mortality agents in suppressing H. armigera populations on tuberose.