Light and electron microscopy studies of the infection of the western flower thrips frankliniella occidentalis (Thysanoptera: thripidae) by the entomopathogenic fungus metarhizium anisopliae

The infection of Frankliniella occidentalis by two isolates of the entomopathogenic fungus Metarhizium anisopliae was studied using fluorescence, scanning, transmission, and confocal scanning laser microscopy techniques. Conidia of M. anisopliae adhered mostly to the wings of adult F. occidentalis but the number declined from 73 to 40% within 72 h postinoculation at 23 degreesC, presumably due to preening. Conidia germinated and produced appressoria on adult, larval, and pupal stages within 12 h post inoculation. However, penetration pegs were not observed until 30 h postinoculation. Light microscopy and transmission electron microscopy provided further information on fungal development inside the insect. The fungus colonized the insect hemocoel from day 3 and sporulated approximately 6 days postinoculation. Copyright 1999 Academic Press.