Liquid media with differing carbon concentrations and
carbon-to-nitrogen ratios were tested for production of desiccation
tolerant blastospores of Paecilomyces fumosoroseus. While
all media tested supported sporulation in submerged culture, high
blastospore concentrations (5·8 × 108 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 higher
percentage (79%) of these blastospores survived air drying. Media
containing glucose concentrations greater than 20 g
l−1 and Casamino acid concentrations between
13·2 and 40 g l−1 supported maximal
production of desiccation tolerant blastospores. All 23 isolates of
P. fumosoroseus grown in MS media produced high
concentrations of desiccation tolerant blastospores. When stored at 4
°C, more than 60% of the lyophilized blastospores produced in MS
medium were still viable after 7 months storage while less than 25%
of the air-dried blastospores survived after 90 d storage. Standard
whitefly bioassays were performed 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
LD50S of 60 and 113 blastospores
mm−3 for the silverleaf whitefly (Bemisia
argentifolii) in two separate bioassays with potency ratios
(LD50B. bassiana/LD50P.
fumosoroseus) of 3·9 and 3·8, respectively. These
results have demonstrated that high concentrations of blastospores of
P. fumosoroseus can be rapidly produced in liquid culture,
remain viable following drying, and infect and kill silverleaf whitefly.