Research Update

By John Kaminski and Maureen Kahiu

Building on previous research investigating the scope of dollar spot resistance to various fungicides in Pennsylvania, research is now under way to determine if differences in resistance exist among fungicides within the demethylation inhibiting (DMI) chemical class. Eight DMI fungicides are currently available, but most resistance studies have relied on propiconazole to represent resistance across the entire chemical class. With variability being observed in the length of dollar spot control among the commercially available products, our research aims to elucidate potential differences in resistance across all DMI fungicides. Field trials were initiated in 2020 at two locations. Commercially available DMI fungicides were applied at various rates and timings and disease monitored. Although data is currently being analyzed, three additional field studies are planned for 2021. Trials will be conducted at golf courses previously identified as having low, moderate, and high levels of resistance to propiconazole. In addition to field studies, isolates of Clarireedia spp. are currently being screened in vitro for resistance across all DMI fungicides. In addition to resistance assays, studies are also being conducted to characterize differences in turfgrass safety among DMI fungicides.