Presence and distribution of entomopathogenic Hirsutella species (Fungi: Sordariomycetes) infecting the mite Phytonemus pallidus in strawberry fields across the province of Québec.

Effective control strategies are needed against Phytonemus pallidus Banks (Acari: Tarsonemidae), a major pest in strawberry worldwide. A total of 25 strawberry (Fragaria × Ananassa Duch.) fields in Québec were surveyed for the presence of P. pallidus naturally mycosed by entomopathogenic fungi (EPF) of the genus Hirsutella (Ascomycota: Sordariomycetes). Parameters such as management type (conventional versus organic), growing system (plastic mulch versus matted rows), and meteorological variables (temperature, precipitation, and relative humidity) were monitored to determine their possible impact on the presence of naturally mycosed P. pallidus. Naturally mycosed P. pallidus were observed on 17 of the sites sampled. The number and the proportion of naturally mycosed P. pallidus relative to their total number were influenced by meteorological variables, but not by management type or growing system. Two species, Hirsutella nodulosa and Hirsutella subulata, were identified on mycosed mites. H. nodulosa was previously reported in the province of Québec while H. subulata is reported in the literature for the first time in Canada. This also represents the first report of H. subulata on a mite. Evaluation of the distribution of these EPF combined with a better understanding of the factors contributing to the spread of mycosis among P. pallidus would enable the development of a conservation biological control strategy against this pest in strawberry fields.