LIQUID CULTURE PRODUCTION OF DESICCATION TOLERANT BLASTOSPORES OF THEBIOINSECTICIDAL FUNGUS PAECILOMYCES-FUMOSOROSEUS

Liquid media with differing carbon concentrations and carbon-to-nitrog en ratios were tested for production of desiccation tolerant blastospo res of Paecilomyces fumosoroseus. While all media tested supported spo rulation in submerged culture, high blastospore concentrations (5.8 x 10(8) spores ml(-1)) were produced in media containing 80 g glucose l( -1) and 13.2 g Casamino acids l(-1) (MS medium) and a significantly hi gher percentage (79%) of these blastospores survived air drying. Media containing glucose concentrations greater than 20 g l(-1) and Casamin o acid concentrations between 13.2 and 40 g l(-1) supported maximal pr oduction of desiccation tolerant blastospores. All 23 isolates of P. f umosoroseus grown in MS media produced high concentrations of desiccat ion tolerant blastospores. When stored at 4 degrees C, more than 60% o f the lyophilized blastospores produced in MS medium were still viable after 7 months storage while less than 25% of the air-dried blastospo res survived after 90 d storage. Standard whitefly bioassays were perf ormed to compare air-dried blastospores of P. fumosoroseus ARSEF 4491 with solid substrate-produced conidia of Beauveria bassiana ARSEF 252. Air-dried blastospores of P. fumosoroseus gave LD(50)s of 60 and 113 blastospores mm(-3) for the silverleaf whitefly (Bemisia argentifolii) in two separate bioassays with potency ratios (LD(50) B. bassiana/LD( 50) P. fumosoroseus) of 3.9 and 3.8, respectively. These results have demonstrated that high concentrations of blastospores of P. fumosorose us can be rapidly produced in liquid culture, remain viable following drying, and infect and kill silverleaf whitefly.