Effect of Synthetic Fungicides Used in Conventional Strawberry Growing System on Hirsutella sp., an Entomopathogenic Fungus of Cyclamen Mite

The study investigated the effect of 17 synthetic fungicides used in strawberry fields in Québec (Canada) on the in vitro growth of Hirsutella sp., an entomopathogenic fungus. Isolates collected from cyclamen mites from farms with a conventional growing system (Hirsutella sp. H94 and Hirsutella nodulosa H98) and from a farm with an organic growing system (H. nodulosa H0) were selected for the study. All the fungicides tested strongly inhibited the mycelial growth of the three isolates, although slight differences in sensitivity were observed. Fullback® 125 SC (A.I.: flutriafol), Mettle® 125 ME (A.I.: tetraconazole), NovaTM (A.I.: myclobutanil), and Quadris top® (A.I.: azoxystrobin and difenoconazole) were the most effective at inhibiting the growth of the three isolates. Property® 300SC (A.I.: pyriofenone) was the fungicide with the lowest inhibiting effect on the growth of the three isolates. Isolates H94 and H98 obtained from farms with a conventional growing system, and thus frequently exposed to synthetic fungicides, did not show resistance to the fungicides tested. The study suggests that fungicides might negatively impact the natural populations of the entomopathogenic fungi of the genus Hirsutella on strawberry plants.