Pathogenicity and formulation of Typhula phacorrhiza, a biocontrol agent of gray snow mold

In previous testing, we found that gray snow mold, caused by Typhula ishikariensis or T. incarnata, could be controlled by applying T. phacorrhiza onto turf grass prior to snowfall. To test for phytopathogenicity of this biocontrol agent, the five most disease-suppressive isolates were cultured on mixed grains and applied to 12 turfgrass cultivars and 2 winter wheat cultivars in December 1995 and 1996. After snow melt in April 1996 and 1997, significantly greater winter injury was visible on plots treated with the pathogens compared to T. phacorrhiza-treated plots or untreated plots. Except for one cultivar in 1996, there were no significant differences between T. phacorrhiza-treated plots and untreated plots. Pelletized alginate formulations of T. phacorrhiza containing kaolin clay with various nutritional amendments were tested for viability and efficacy. After 64 weeks of storage, viability remained >85% at -15 degrees C and >70% at 4 degrees C, but <30% at 10 degrees C and 25 degrees C. Significant control of gray snow mold by T. phacorrhiza using small numbers of pellets (20 g/m(2)) was equivalent to using larger amounts of mixed grain inoculum (200 g/m(2)) or wheat bran inoculum (100 g/m(2)) in 2 years of field testing.