Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/12/2001
Publication Date: 8/1/2001
Citation: ALTRE, J.A., VANDENBERG, J.D. PENETRATION OF CUTICLE AND PROLIFERATION IN HEMOLYMPH BY PAECILOMYCES FUMOSOROSEUS ISOLATES THAT DIFFER IN VIRULENCE AGAINST LEPIDOPTERAN LARVAE. JOURNAL OF INVERTEBRATE PATHOLOGY. 2001. v. 78. p. 81-86. Interpretive Summary: The diamondback moth is a worldwide pest of cruciferous vegetables. Each year, farmers spend more than $1 billion to control this pest, primarily with chemical insecticides. However, many populations of diamondback moth have become resistant to conventional, as well as some biological, insecticides. Alternative control measures being investigated include the use of insect-pathogenic fungi, but basic studies of fungal infection processes are needed for selection of appropriate strains. For two strains, we compared how readily they penetrated insect cuticle and how quickly they proliferated within the insect bloodstream. We found that the highly infectious strain penetrated cuticle readily and multiplied quickly inside the insect body. The least infectious fungal strain failed to penetrate the cuticle. When we injected spores of this strain into insects, they multiplied slowly but did ultimately cause infection. These findings further our understanding of the disease process and help us focu our efforts on finding strains that are efficient at penetrating the outer cuticle of insects.
Technical Abstract: Frequency of cuticular penetration and speed of proliferation in hemolymph were compared between 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 30 h after inoculation. Virtually no penetration was observed for isolate 1576 after 30 h. Isolate 4461 also proliferated more quickly than isolate 1576 in the hemolymph of fall armyworm.