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

A 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.