|Vidal, Claire - FRANCE|
|Fargues, Jacques - FRANCE|
Submitted to: Mycopathologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 9, 1998
Publication Date: N/A
Interpretive Summary: The silverleaf whitefly is a serious pest in greenhouses and arid growing regions worldwide including Texas, California, and Arizona. This insect pest has become resistant to numerous chemical control measures. The fungus, Paecilomyces fumosoroseus, is an aggressive disease-causing organism in the silverleaf whitefly and is being developed as a biological control agent. The commercial potential of microbial biocontrol agents is dependent on the availability of cost-effective mass production methods. In this study, various liquid culture fermentation media were compared based on their ability to produce high concentrations of spores of P. fumosoroseus and on their ability of these spores to infect and kill the silverleaf whitefly. Of the five liquid media tested, three diets supported high P. fumosoroseus spore yields, and the spores produced showed maximum effectiveness in infecting and killing the silverleaf whitefly. One of the best liquid media (Jackson medium) is under commercial development in a collaborative agreement between ARS and industrial scientists. The development of P. fumosoroseus as a bioinsecticide for the control of the silverleaf whitefly will provide farmers and greenhouses with a biorational tool for controlling this agronomic pest.
Technical Abstract: The entomopathogenic Hyphomycete Paecilomyces fumosoroseus was grown in five different liquid media, which have been developed for mass production of Beauveria spp. or P. fumosoroseus. Production was followed for 96 h by measuring both biomass and the concentration of propagules. Maximal biomass was obtained with two media, Jackson and Catroux media (40 to 60 mg gml**-1 suspension produced after 42 h incubation), where the exponential phase of growth began earlier than in the other media. While high concentrations of propagules (1.4 to 5.5 X 10**8 propagules ml**-1) were produced in three media (Jackson, Paris, and Catroux media) after 48 to 72 h incubation, production of propagules was lower in the two other media, containing maltose as carbon source (Goral and Kondryatiev media) with 0.4 to 3.7 X 10**7 propagules ml**-1 after 96 h incubation. P. fumosoroseus produced blastospores more or less oblong in the three most productive media and conidiospore-like (ovoid to subspherical) propagules in the two other media. Infection potential of produced propagules was tested on the silverleaf whitefly (Bemisia argentifolii), a serious insect pest in field and greenhouse crops worldwide. Whiteflies were sprayed as 2nd instars with P. fumosoroseus propagules produced in the five liquid media (1.9 X 10**3 and 1.9 X 10**4 propagules cm**-2). All the media produced propagules that were infectious for B. argentifolii larvae. With the lower dosage, mortality rates were significantly lower with propagules produced in one of the two least productive media (57%) (in the Kondryatiev medium) compared to those obtained with the three most productive media (>90%). However, when whiteflies were treated with the higher dosage, mortality rates (91 to 99%) between media were not significantly different.