THE IMPLICATION OF METABOLIC ACIDS PRODUCED BY BEAUVERIA-BASSIANA IN PATHOGENESIS OF THE MIGRATORY GRASSHOPPER, MELANOPLUS-SANGUINIPES

The entomopathogenic fungus, Beauveria bassiana, produced oxalic and citric acids in liquid cultures containing grasshopper (Melanoplus sanguinipes) cuticle as the sole nutrient source. Oxalic and citric acids solubilized cuticular proteins as well as commercial preparations of elastin and collagen. Other organic acids which solubilized cuticular proteins included acetic and formic acids. In contrast to these organic acids, the inorganic acids, hydrochloric acid and sulfuric acid, did not solubilize or only slightly solubilized cuticular proteins when compared to the organic acids. M. sanguinipes treated with B. bassiana showed a LT50 of 7.33 days, while M. sanguinipes treated with citric acid or oxalic acid showed a LT50 of 7.25 and 13.28 days, respectively. M. sanguinipes treated with citric acid followed by a B. bassiana conidia treatment showed a LT50 of 3.88 days, and the oxalic acid. B. bassiana treatment resulted in a LT50 of 5.08 days. Analysis of the bioassay data revealed that the relationship between oxalic acid or citric acid together with B. bassiana conidia in grasshopper mortality was markedly synergistic. We suggest that acid metabolites produced by B. bassiana may play a role in cuticle solubilization and subsequent hyphal penetration. © 1991.