Challenging the larvae of <Emphasis Type="Italic">Helicoverpa armigera</Emphasis> and assessing the immune responses to nematode-bacterium complex

Helicoverpa armigera is a strong insecticidal resistance developed insect pest. The understanding of its innate immune responses to emerging biocontrol agent entomopathogenic nematode-bacterial complex can provide an opportunity to control this insect in an environmentally benign manner. Study was focused on role of hemocytes changes and PO activity in Steinernema abbasi-Xenorhabdus indica challenged larvae of H. armigera over the time. Total cell count changed effectively from 10.2?±?1.81?×?10⁵ to 15.5?±?3.3?×?10⁵ cells/mm³ upto 9 h and reduced distinctly up to 8.0?±?2.49?×?10⁵ cells/ mm³ in 24 h. PO activity inclined significantly and was recorded highest at 9 h (24.67?±?1.08?×?10² units) and lowest at 24 h (14.34?±?0.74?×?10² units) in total hemolymph with a similar pattern in plasma and the cellular fraction. Phenoloxidase activity in total and cellular component of hemolymph was positively correlated with prohemocytes, granulocytes and oenocytoids. Study showed the hemocytes and PO accounted as active immune responses against nematode infection. The results provide the first insight to understand the hemolytic activity, quick immunosuppression responses of S. abbasi-X. indica and vulnerability of H. armigera.