Submitted to: Entomology International Congress Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 8/26/2000
Publication Date: N/A
Technical Abstract: A major constraint to the commercial use of fungal biopesticides has been the lack of low-cost mass production methods that yield high concentrations of stable, infective propagules, usually in the form of fungal spores. In order to assess the commercial potential of these pathogens, a screening protocol was developed to evaluate the amenability of these isolates to liquid culture spore production. Spore yields were measured for various fungal entomopathogens grown in six nutritionally different liquid media. In this study, six fungi were tested: two Beauveria bassiana strains, two Paecilomyces fumosoroseus strains, one P. farinosus strain, and one Metarhizium anisopliae strain. Spore yields were examined after 2, 4, or 7 days growth. Highest spore yields were obtained in media containing 36 g/L and a CN ratio of 10:1. After 4 days growth, highest spore yields were measured in the three Paecilomyces isolates (8.3 22.9 X 10**8 spores/mL). Spore production by the B. bassiana isolates was variable with one isolate producing high spore yields (12.2 X 10**8 spores/mL) after 7 days growth. The M. anisopliae isolate produced low spore yields under all conditions tested. The ability of the P. farinosus strain (isolated from the coffee berry borer, Hypothenemus hampei) to rapidly produce high concentrations of spores (22.9 X 10**8 spores/mL in 4 days) prompted further testing to determine the desiccation tolerance of these spores. Liquid culture produced P. farinosus spores were mixed with diatomaceous earth and air-dried overnight at 23 deg C with moist air (RH>60%). Germination assays showed that 80% of the spores survived air-drying. In this study, P. farinosus was shown to possess the production and stabilization attributes required for commercial development.