Penetration of cuticle and proliferation in hemolymph by Paecilomyces fumosoroseus isolates that differ in virulence against lepidopteran larvae

Frequencies of cuticular penetration and speed of proliferation in hemolymp h were demonstrated for two isolates of Paecilomyces fumosoroseus that diff er in virulence against diamondback moth, Plutella xylostella. Penetrant hy phae 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 f or up to 52 h after inoculation. Isolate 4461 also proliferated more quickl y than isolate 1576 in the hemolymph of fall armyworm when the isolates wer e injected as blastospores. (C) 2001 Academic Press.