Cellular Immune Response of Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae) during Mycosis of the Entomopathogenic Fungus Beauveria bassiana (Balsamo) Vuillemin

Abstract

Beauveria bassiana one of the most common and ubiquitous entomopathogens, is known to be a highly potential bioagent for the control of insects belonging to various orders. The cellular immune response was examined in Spodoptera litura larvae infected with B. bassiana. Third instar larvae were treated with a fungal suspension @ 2.03x10⁸ spores ml^-1. Haemolymph of treated and untreated larvae were taken after 2, 12, 24,48,72, 96 and 120 hours after inoculation. Plasmatocytes and granulocytes swelled 2 hours after inoculation (HAI) followed by lysis of plasma membrane. Within 24 HAI, apposition was observed. The encapsulation process started after 48 hours and continued for up to 72 hours. After 96 hours of inoculation the granulocytes and plasmatocytes were observed to form nodules. With increasing inoculation time, the size of clump increased, forming multiple layers at 120 HAI. However, despite these insect defense responses, growth of fungal hyphae was observed after 120 hours of inoculation which ultimately resulted in the death of the host.