Frequencies of cuticular penetration and speed of proliferation in hemolymph were demonstrated for two isolates of Paecilomyces fumosoroseus that differ in virulence against diamondback moth, Plutella xylostella. Penetrant hyphae of virulent isolate 4461 were visible in larval cuticle cross-sections of diamondback moth and fall armyworm, Spodoptera frugiperda, within 22 h after inoculation. Virtually no penetration was observed for isolate 1576 for up to 52 h after inoculation. Isolate 4461 also proliferated more quickly than isolate 1576 in the hemolymph of fall armyworm when the isolates were injected as blastospores.
Department of Entomology, USDA Agricultural Research Service, Cornell University, U.S. Plant, Soil, and Nutrition Laboratory, Tower Road, Ithaca, New York 14853, USA.
