The broad mite is a pest of many important crops. Pathogens have potential as control agents, but only one species has been reported in association with broad mite. Because broad mite develops best when relative humidity is 75-90%, and entomopathogenic fungi require 90-100%, fungi might be good biological control agents. Three fungi were investigated in the lab for their ability to infect broad mite.
Conidial suspensions of Beauveria bassiana, Hirsutella thompsonii and Paecilomyces fumosoroseus were applied to detached bean leaves infested with broad mites in Petri dishes. All isolates tested were able to infect broad mite. Infection by B. bassiana was first observed 2 days after fungi were applied, and reached peak infection after 6 days; the other fungi had incubation periods of 2-6 days, with peak mortality 6 days after application. H. thompsonii had the highest level of virulence, followed by P. fumosoroseus; B. bassiana had the lowest virulence in these lab trials. B. bassiana effectively spread from infected cadavers to new mites only when mite populations were high, whereas the spread of P. fumosoroseus was less related to population density.
B. bassiana and P. fumosoroseus were also applied either alone or with adjuvants to broad mite-infested plants in the greenhouse (H. thompsonii didn't easily produce enough spores for the required sprays). B. bassiana caused much more mortality than P. fumosoroseus, and by the end of the experiment was as effective as the comparison acaricide (based on Bacillus thuringiensis Beta-exotoxin). This acaracide rapidly suppressed population growth during the first 6 days after treatment, while B. bassiana worked more slowly. Adjuvants added to the sprays did not increase infection.
Peņa, J. E., L. S. Osborne, and R. E. Duncan. 1996. Potential of fungi as biocontrol agents of Polyphagotarsoneumus latus. Entomophaga 41(1): 27-36.
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