Deposition and germination of conidia of the entomopathogen Entomophaga maimaiga infecting larvae of gypsy moth, Lymantria dispar

Germination of conidia of Entomophaga maimaiga, an important fungal pathogen of gypsy moth, Lymantria dispar, was investigated on water agar and larval cuticle at varying densities. Percent germination was positively associated with conidial density on water agar but not on larval cuticle. When conidia were showered onto water agar, the rate of germination was much slower than on the cuticle of L. dispar larvae. From the same conidial showers, the resulting conidial densities on water agar were much higher than those on larval cuticle in part because many conidia adhered to setae and did not reach the cuticle. A second factor influencing conidial densities on larval cuticle was the location conidia occurred on larvae. Few conidia were found on the flexible intersegmental membranes in comparison with the areas of more rigid cuticle, presumably because conidia were physically dislodged from intersegmental membranes when larvae moved. Conidia were also exposed to heightened CO2 to evaluate whether this might influence germination. When conidia on water agar were exposed to heightened CO2 levels, germinating conidia primarily formed germ tubes while most conidia exposed to ambient CO2 rapidly formed secondary conidia. (C) 2002 Elsevier Science (USA). All rights reserved.