Lawn and Turf-Typhula Blight (Gray Snow Mold)

Host All grasses are susceptible.

Cause Typhula incarnata and T. ishikariensis, fungi that grow and attack dormant plants at low temperatures under snow cover. Typhula incarnata is "Gray Snow Mold" and needs 60+ days of snow cover and T. ishikariensis is "Speckled Snow Mold" and needs less than 60 days of snow cover and in some cases, fog and light rain can promote disease development. They can survive the hot dry summer months as sclerotia (a compact mass of hardened mycelium stored with food reserves). In fall, they germinate under cool, moist conditions. Snow cover will predispose plants to attack by these fungi and the disease is worse the longer snow is on the ground. These fungi are most active under snow that has fallen on unfrozen ground. This is especially true for grass cut high and for short-cut golf course turf such as greens and tees. Snow is not necessarily needed for damage to occur from these fungi. Disease is worse on lawns with heavy thatch layer.

Symptoms After snow recedes, the disease appears as small (3 to 6 inches), roughly circular, water-soaked spots turning yellow to yellow-brown. Under prolonged snow, spots often are larger (up to 12 inches); they are white to gray-white and covered with a fluffy white to gray mass of fungal growth. Under favorable conditions, spots may enlarge with a gray halo of fungal growth on the margin. Generally only leaves, not crowns, are attacked; plants grow back to a normal appearance. However, in severe conditions, crowns may not regrow.

Cultural control

• Use a balanced fertilizer; avoid heavy nitrogen applications in late fall. Use no more than 0.5 lb nitrogen/1,000 sq ft per application. Ammonium nitrate or ammonium sulfate are recommended nitrogen sources for fall applications.
• Improve air and soil drainage and reduce thatch by aerifying.
• Rake and remove tree leaves from lawn before snowfall.
• Continue to cut grass until snowfall and remove clippings.

Chemical control Both Microdochium patch and Typhula snow mold may be in the same area at the same time and often intermingle. When spraying, add a fungicide to control Microdochium and apply before snowfall. For adequate control, use materials and/or tank mixes with multiple fungicide groups in which one is a broad spectrum (multi-site, contact) fungicide such as chlorothalonil to get adequate control. Applying fungicides too early may be followed by continued plant growth and/or rainfall. These conditions may dilute the fungicide and result in poor control. Use higher rates for areas with longer snow cover.

Products available in home packaging:

• Infuse Systemic Disease Control at 5 fl oz/1 gal water/250 sq ft of lawn. Group 3 fungicide. H

Products available for commercial use:

• Chipco 26019 FLO at 4 to 8 fl oz/1,000 sq ft. Group 2 fungicide. 12-hr reentry.
• Daconil Weather Stik at 5.5 fl oz/1,000 sq ft. Group M5 fungicide. 12-hr reentry.
• Densicor at 8.5 fl oz/A or 0.196 fl oz/1,000 sq ft. Do not use hand held equipment. Group 3 fungicide. Reenter when sprays have dried.
• Disarm 480 SC at 0.36 fl oz/1,000 sq ft. plus another fungicide with a different mode of activity. Group 11 fungicide. 12-hr reentry.
• Fame SC at 0.2 fl oz/1,000 sq ft plus another fungicide. Group 11 fungicide. 12-hr reentry.
• Heritage at 0.4 oz/1,000 sq ft. Group 11 fungicide. 4-hr reentry.
• Insignia SC at 0.7 fl oz/1,000 sq ft. plus another fungicide with a different mode of action. Do not use with organosilicate adjuvants. Group 11 fungicide. 12-hr reentry.
• Medallion SC at 2 fl oz/1,000 sq ft. Tank-mix with another fungicide. Using with oils or adjuvants may damage plant. Group 12 fungicide. 12-hr reentry.
• Mirage at 1 to 2 fl oz/1,000 sq ft plus another fungicide. Group 3 fungicide. 12-hr reentry.
• Monsoon Turf at 0.6 fl oz/1,000 sq ft. Group 3 fungicide. 12-hr reentry.
• Previa at 4 to 5.5 fl oz/1,000 sq ft. Group M5 fungicide. 12-hr reentry.
• Propiconazole-based products. Apply once in fall. Group 3 fungicides.
  • Banner MAXX at 2 to 4 fl oz/1,000 sq ft. 12-hr reentry.
  • PropiMax EC at 0.73 to 1.45 fl oz/1,000 sq ft. 12-hr reentry.
• ProStar 70 WG at 3 to 4.5 oz/1,000 sq ft plus a wetting agent. Group 7 fungicide. 12-hr reentry.
• Secure at 0.5 fl oz/1,000 sq ft plus another fungicide. Group 29 fungicide. Reentry when sprays have dried.
• Spotrete F at 12 fl oz/1,000 sq ft plus a latex-based sticker. Repeat applications at each thaw with 3 fl oz/1,000 sq ft. Group M3 fungicide.24-hr reentry.
• Tebuzol 3.6F at 0.6 fl oz/1,000 sq ft plus another fungicide. Group 3 fungicide. No reentry interval listed.
• Torque at 0.6 to 1.1 fl oz/1,000 sq ft. Do not mix with growth regulators during hot weather as injury may develop. Group 3 fungicide. 12-hr reentry.
• Tourney EZ at 0.37 to 0.44 oz/1,000 sq ft. plus other fungicides. Poor results using this fungicide in Colorado. Do not apply to Poa annua putting greens Group 3 fungicide. 12-hr reentry.
• Trinity at 0.5 to 2 fl oz/1,000 sq ft. Do not mix with growth regulators during hot weather as injury may develop. Group 3 fungicide. 12-hr reentry.
• Turfcide 400 at 12 to16 fl oz/1,000 sq ft. Irrigate with 0.25 inch water (or rainfall) immediately after application. Do not use hand application equipment. Under certain growing conditions a temporary discoloration of the grass may occur. Group 14 fungicide. 12-hr reentry.
• Velista at 0.7 oz/1,000 sq ft plus another fungicide. Group 7 fungicide. 12-hr reentry.
• Xzemplar at 0.26 fl oz/1,000 sq ft. Group 7 fungicide. 12-hr reentry.

Combination Fungicides

• Concert at 5.5 or 8.3 fl oz/1,000 sq ft. Do not use on fine fescue turf. Group 3 + M5 fungicide. 12-hr reentry.
• Contend A at 1 fl oz/1,000 sq ft, one application only. Mix with another fungicide for greens. Group 3 + 7 fungicide. Reentry when sprays have dried.
• Contend B at 4.5 fl oz/1,000 sq ft plus another fungicide from a different FRAC group. Group 3 + 11 fungicide. Reentry when sprays have dried.
• Headway at 3 fl oz/1,000 sq ft. Do not use with silicone-based surfactants or EC formulations. Group 3 + 11 fungicide. 12-hr reentry.
• Heritage Action at 0.4 oz/1,000 sq ft. Alternate with other fungicides. Group 11 + P1 fungicide. 12-hr reentry.
• Honor at 1.1 oz/1,000 sq ft. plus another fungicide. Do not use with organosilicone-based adjuvants. Group 7 + 11 fungicide. Golf course turf only.
• Instrata at 5 to 11 fl oz/1,000 sq ft. See label for tank mix incompatibilities. May need to add additional amounts of Medallion to be effective. Do not use on fine fescue. Group 3 + 12 + M5 fungicide. 12-hr reentry.
• Interface at 4 to 7 fl oz/1,000 sq ft. Maintain agitation while spraying. Do not mix with adjuvants. Group 2 + 11 fungicide. 24-hr reentry.
• Lexicon at 0.47 fl oz/1,000 sq ft. Group 7 + 11 fungicide. 12-hr reentry.
• Navicon at 0.85 fl oz/1,000 sq ft. Group 3 + 11 fungicide. 12-hr reentry.
• Pillar G at 3 lb/1,000 sq ft. Label suggests to use another fungicide prior to this application. Group 3 + 11 fungicide. 12-hr reentry.
• Premion at 8 to 12 fl oz/1,000 sq ft. Group 3 +14 fungicide. Reentry when sprays have dried.
• Tartan at 1 to 2 fl oz/1,000 sq ft. Group 3 + 11 fungicide. 12-hr reentry.

Note: Higher turf ratings have been observed after snow melt when fungicides are combined with pigments (such as Stressgard, PAR SG, Ambient, or Foursome). It is thought that the coloring effect (which only lasts about two weeks) helps with better heat absorption and spring green up.

References Blunt, T., Tisserat, N., and Koski, T. 2013. Typhula blight severity as influenced by the number of preventive fungicide applications and snow compaction. Plant Health Progress doi:10.1094/PHP-2013-0821-01-RS.

Hsiang, T., Matsumoto, N., and Millett. S.M. 1999. Biology and management of Typhula snow molds of turfgrass. Plant Disease 83:788-798.

McDonald, B.W., and Kowalewsk, A.R. 2014. Evaluation of fungicides for preventative control of gray snow mold in central Oregon, 2010 - 2011. Plant Disease management reports 8:T040.