Submitted to: Society for Invertebrate Pathology Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 7/21/2009
Publication Date: N/A
Technical Abstract: The Mormon cricket (Anabrus simplex), a tettigoniid, is a major pest of crops and rangeland in the western United States. Beauveria bassiana is an entomopathogenic fungi that serves as a biological control agent of this pest and other grasshoppers. Adult Mormon crickets were drawn from a topical bioassay of B. bassiana Strain GHA using doses of 5.13x10(4)-1.75x10(6) conidia in sunflower oil, with oil only as a control. After incubating the insects for three weeks at 28°C, by which point mortality ranged from 25-80%, we assessed hemolymph phenoloxidase (PO) and lysozyme-like activities of survivors (five males and five females for each treatment, fewer if there were not enough survivors), and scanned a sample of their hemolymph for fungal cells. As expected, adult mortality increased with conidial dose, and there was a significant decrease in body mass that generally paralleled the dose. Phenoloxidase activity was significantly less PO activity in a post hoc comparison of the means. There was no difference in lysozyme-like activity between the treatments. Hence Mormon crickets had elevated levels of PO but not lysozyme in defense against Beauveria infection. PO activity was elevated to the same level independent of infection intensity (dose) in these surviving insects. PO activity of survivors with fungal cells visible in their hemolymph did not differ significantly from those with clear hemolymph. We conclude that circulating PO may be an important enzymatic defense against Beauveria infection, and that it is associated with attempted clearing of Beauveria blastospores and hyphae from the hemolymph of Mormon crickets.