the Northeastern APS Meeting in Bromont, Quebec, 4 October 2002.

New York State Turfgrass Association meeting at Lake Placid, New York, 4 March 2003

• fungi which grow at low temperatures often under snow cover, and can cause damage to plants
• turfgrass snow molds include:
• Gray snow mold
• Typhula incarnata (Tinc)
• Typhula ishikariensis (Tish)
• Pink snow mold
• Microdochium nivale (MN)

• caused by Typhula ishikariensis (Tish) and Typhula incarnata (Tinc) - basidiomycetes
• attack grasses and cereals
• require > 90 days of snow cover for severe disease

• patches up to 10" (25 cm) after snowmelt
• gray-white mycelium on outer edges
• mycelium is the fungal body made of fine threads (10 micrometers wide = 1/40,000 inch)
• small black or red sclerotia in patches
• patch centers matted down

• caused by Microdochium nivale (MN, an ascomycete), also causing Fusarium patch
• attacks grasses and cereals
• requires snow cover and long wetness periods for round patches to form on turfgrasses

• patches up to 8" (20 cm) after snowmelt
• white to pink mycelium on outer edges
• On KB, white patch with red margin
• On CB, reddish-brown patch

• Why is it important to distinguish between pink or gray snow mold diseases? (2 marks)
• Fusarium patch
• fungicide efficacy

• What are differences between pink and gray snow mold diseases? (4 marks)

• minimize thatch
• minimize succulence into winter
• avoid snow compaction
• near end of winter remove snow, or melt it
• rake matted damaged areas

• commonly controlled on turfgrass with heavy metal & chlorinated fungicides
• mercury fungicides (No longer legal in Canada as of December 2000)
• quintozene (pentachloronitrobenzene)

• common fungicide strategies include:

• use a good Fusarium patch chemical by mid fall
• dicarboximides, DMIs, benzimidazoles

• before snow cover, apply snow mold chemical
• pentachloronitrobenzene, DMIs, combinations

• the costs of applying these synthetic fungicides coupled with environmental concerns requires alternative management approaches
• Hudson, Quebec (pesticide ban 2000)
• Cobalt, Ontario (pesticide ban 2002)
• other municipalities in Canada

• minimize thatch
• thatch decreases turf vigor, and sclerotia oversummer there

• avoid succulent, lush growth in late fall
• mow until leaf growth stops
• fast-release nitrogen applied 6 weeks or more before dormancy

• rake up leaves in fall (and spring)

• avoid snow compaction
• compacted ice layers stay around longer

• prevent snow drifts and accumulation in sensitive areas
• snow fencing, windbreak plantings

• snow removal
• to interrupt the 3-month snow cover, physically remove snow or enhance snow melt with dark colored materials or light fertilizer application as you approach the end of winter
• be careful that you don't remove snow cover when air temperatures are still low enough to harm growth (use temperature probes under cover)

• can enhance turf green-up
• provide good conditions for diseases
• often use 2x fungicide rates

• fall fertilizers to enhance spring green-up

• cultural techniques may reduce the severity of snow mold diseases, but cannot entirely prevent their occurrence

• after snowmelt, rake matted areas to encourage drying

• take cup-cutter plug
• wet & place in plastic bag
• put under light at > 20C (70F)
• check for regrowth

• Composts to suppress snow molds; some of this may be a nitrogen effect, and some may be from antagonistic organisms
• Dr. Eric Nelson at Cornell
• Composts are variable mixtures
• Some composts contain hard materials that may interfere with greens mowers

• previous research found that a fungus called Typhula phacorrhiza (TP) is antagonistic to gray snow mold
• this fungus is common all over the world
• it lives on dead plant tissues (saprophyte)

• to collect hundred of isolates of TP
• to test isolates in the lab for growth and production of sclerotia
• to test isolates in the field for snow mold control

• collected over 300 isolates of TP
• large variation in ability of TP isolates to suppress snow mold
• best TP isolates active against snow mold caused by Tish or Tinc
• best TP isolates not pathogenic to grasses in field tests

• to continue efficacy trials with TP across Canada
• to develop a formulation for TP
• to prepare a registration package for TP

• Pest Management Regulatory Agency (Health Canada) regulates pest control products in Canada. They require the following information for registration
• product characterization
• environmental toxicology of product
• human and animal toxicology of product
• efficacy of product

• Performance & Efficacy
• trials established across Canada (1998-2002)

• better formulations
• better TP production methods
• search for better isolates