Submitted to: Journal of Industrial Microbiology
Publication Type: Abstract Only
Publication Acceptance Date: August 9, 1996
Publication Date: N/A
Technical Abstract: The fungus Paecilomyces fumosoroseus is known to infect and kill silverleaf whitefly, Bemisia tabaci. The development of low-cost methods for producing desiccation tolerant, efficacious P. fumosoroseus blastospores is a requirement for commercialization of this biocontrol agent. In this study, we investigated the effect of culture nutrients on P. fumosoroseus desiccation tolerance. Two media, with differing nitrogen sources, were studied: a complex medium, containing Casamino acids (MS medium), and a synthetic medium, containing glutamic acid (GA medium). Yields at 4 day growth were comparable (2-5 x 10**8 blastospores/ml) in MS and in GA media. MS or GA-grown blastospores were dried using three different methods: drying on silica gel, air-drying of blastospores mixed with diatomaceous earth, and freeze-drying. Blastospore germination was assessed immediately after drying to evaluate survival. No significant difference in survival was found between MS and GA-grown blastospores after air-drying (25-50% germination) or after freeze-drying the spores in the spent medium (~75% germination). When dried on silica gel, significantly more GA-grown blastospores survived drying (41%) compared to MS-grown blastospores (23%). When blastospores were rinsed with water and freeze-dried, fewer MS-grown blastospores survived drying (9%) compared to GA-grown blastospores (46%). These results suggest that blastospore survival is influenced by nutritional conditions during growth and sporulation and by the method of drying.