Pathogenesis of Entomopathogenic Fungus, Metarhizium anisopliae (Metsch.) Sorokin., on Mealybug, Paracoccus marginatus (Williams and Granara De Willink) (Homoptera:Pseudococcidae)

A study was conducted to investigate the basis and mode of infection of the entomopathogenic green muscardine fungus, Metarhizium anisopliae on the mealybug, Paracoccus marginatus. The pathogenesis of M. anisopliae on P. marginatus was studied at 24, 48, 72, 96, 120, 144 and 168 hours after inoculation. The conidial adhesion and germination process of M. anisopliae occurred within 24 hours after inoculation. The hyphae penetrated the epicuticle and reached the endocuticle within 48 to 72 hours after inoculation. Lysis of the endocuticle occurred while the penetrant hyphae invaded into the epidermis. Invasion and colonization of hyphal bodies into the haemocoel of P. marginatus was observed at 72 to 120 hours after inoculation. By 120 to 144 hours after inoculation, there was considerable abundance of hyphae that extensively colonized on the host and complete invasion occurred at 168 hours after inoculation. At this stage, the larvae became moribund and died. Hyphae re-emerged out of the cuticle after 168 hours after inoculation, and grew all over the surface forming a green mycelial mat. The developmental cycle of M. anisopliae on P. marginatus took 172 to 196 hours to disintegrate and kill the insect from the day of inoculation.