Now is the time to start thinking about snow mold prevention. Ken Hutto, Ph.D., product development manager for herbicides and fungicides for FMC, sat down with Landscape Management to help contractors understand how snow mold symptoms can start and why snow mold preventative applications are important.
LM: What snow mold symptoms would LCOs see first?
KH: For Typhula snow molds (gray and speckled), initial symptoms can begin as small as 1-2 inch diameter patches that are pale green/yellow. Once under snow cover, the mycelial growth of the fungi increases creating, larger patches (6 to 12 inches) that are gray to white. These patches are not generally observed until snow cover has subsided.
During snowmelt, white mycelium — fungal threads of the pathogen — can be observed on the margins of the patches. Blighted leaf tissue eventually mats together and smaller patches can aggregate into much larger patches. Gray and speckled snow mold produce distinct sclerotia — larger groups of mycelium. Gray snow mold sclerotia are reddish-brown while speckled snow mold sclerotia are smaller and black. These sclerotia can be found on dead leaf blades.
Pink snow mold/microdochium patch symptoms develop as small, circular patches 2 to 3 inches in diameter with a gray to white color. Under cool, moist conditions, pink mycelium can be observed around the border of individual patches. Disease activity under snow can result in larger patches of gray to white due to blighted or matted down turf. White to pink mycelium can be observed around the patch borders as snow cover melts.
Patches forming in an area with a high percentage of Poa annua may develop rust-colored borders.
LM: Is there anything else an LCO might mistake snow mold symptoms for?
KH: Once snow cover breaks, gray snow mold symptoms may be mistaken for winter desiccation of turfgrass.
LM: What are some mistakes LCOs might make when dealing with a lawn with snow mold?
KH: Fertilizing too late in the fall with soluble nitrogen fertilizers. This produces an excess flush of growth around the time environmental conditions favor disease development.
LM: How can LCOs work with homeowners to understand the benefit of snow mold preventative treatments as opposed to curative treatments?
KH: Preventative control using fungicides is the most effective way to control snow mold. It is recommended that preventative applications be made prior to the first snowfall, typically between late October to early November, depending upon the geographical location. The most effective snow mold control programs incorporate both contact and systemic fungicides. In certain geographies where cool, moist conditions persist late in the year, a second fungicide application may be warranted.
LM: Is there anything else an LCO might want to know/think about snow mold?
KH: Mowing turfgrass until dormancy will maintain a consistent height of cut and reduce the potential for matted down areas where disease can develop. In spring, raking away matted areas and normal fertilizer applications will aid in turfgrass recovery for those areas where severe damage did occur. LCOs can also use cultural practices to reduce thatch buildup. If possible, minimizing the amount of time a particular area is under snow can help in reducing snow mold infestation.
