Study Examines Snow Mold Solutions for Northwest

Pink snow mold (Mirodochium patch) and gray snow mold [Typhula blight) are the most prevalent and destructive winter diseases on cool-season turfgrass in the northern United States. They are especially destructive in the Intermountain Northwest where deep snow cover may last four to five months. Pentachloronitrobenzene (PCNB, Quintozene) has been use to manage these diseases in turf on golf courses for many years. When used alone over time, pathogen resistance may develop, as well as other turf and environmental problems. We sought to identify new chemistry and combinations of compounds that could be used in rotation with PCNB. Research was conducted on golf course bentgrass (Agrostis stolonifera L .)/Poa annua golf greens and nurseries during a three-year period (2000-2003). In locations with mild to moderate winters, many of the older chemistry fungicides used alone, or in combination with a compound with newer chemistry, gave good control. In locations with prolonged snow cover, combinations of two and possible three fungicides are needed for adequate control. Gray snow mold is generally associated with Numerically (but not statistideep prolonged snow cover, often greater than cally different from all other treat100 days. ments, overall sites and years), the treatment with the best control with good spring turfgrass quality was Medallion 50WP + Banner MAXX 1.3MEC + Daconil Ultrex 82.5WDG. Traditionally, fungicide applications are the primary means to control or manage (terminology preferred by Vargas, 1994) pink snow mold and gray snow mold. Evidence suggests that resistant strains of snow-mold fungi have developed with continued use of fungicides (Chastagner and Vassey, 1982). PCNB phytotoxicity has also been reported, especially when PCNB is used at the upper end of the labeled rate Continued on page 66 • Ultradwarf Bermudagrasses Exhibit Easy Mutation Tendencies, Part II 74