Histopathology of Nomuraea rileyi in larvae of Heliothis zea and in vitro enzymatic activity

Conidia of Nomuraea rileyi germinated in 2 days on larvae of Heliothis zea. Germ tubes penetrated the cuticle directly. This seemed to be aided by enzymatic secretions as evidenced by the darkening of the epicuticle and part of the exocuticle suggesting apparent lysis. In the endocuticle, hyphae grew parallel to the endocuticular laminae with lateral branches penetrating into epidermis and then hemocoel where they proliferated and attacked internal organs. Blood cells were first to be invaded, followed by fat lobes, Malpighian tubules, muscles, and mesenteron. Disintegration of body tissues of the host began before death. At death, hyphae began to grow outward. In vitro enzymatic tests showed that N. rileyi secretes chitinase, protease, and lipase.