Winter is coming. There's no denying it. So, we talked to Paul Koch from the plant pathology department at the University of Wisconsin, about how to prevent and control snow mold.
What are the trends going on with snow mold in research?
Snow mold is actually an umbrella term for several different diseases; the most common ones being pink snow mold (Microdochium patch), gray snow mold (Typhula incarnata), and speckled snow mold (Typhula ishikariensis). Because the fungi that cause these diseases grow so slowly and doing research in winter is difficult, there is not a lot of research on snow mold relative to summer diseases.
However, some recent research out of Cornell University suggested that high potassium fertilizer late in the season promoted more snow mold, and researchers out of Colorado State University showed that one fall fungicide application is often just as effective as two fall fungicide applications for controlling snow molds and also that areas compacted by skiing or snowmobiling showed reduced levels of snow mold. Here at Wisconsin we have shown that snow mold fungicides applied in the fall degrade rapidly under melting snow or during winter rainfall events but otherwise persist for significant periods of time whether under snow or no snow if the soil is frozen. In addition, we have looked at some issues involved with the timing of snow mold fungicides.
What kind of issues?
The question is when is the right time to put down your fungicide application? We’ve been asking if the closer to the snow cover coming down the better for handling the snow mold, but that’s not what we’re finding.
We have shown in our research that it’s not really the best thing. I’m not saying the fungicide has to go down in September, that’s detrimental too, but they don’t have to go down as the snow comes down either.
We’ve suggested putting down another application earlier on than the original time. It could be anywhere from early to late October, with the second application coming closer to the actual snowfall event. The thing is, with that first application, we want to knock down the initial growth of the fungus, three to four weeks before the first snow event.
Snow mold can get started that early?
The fungus is usually starting to grow and interact with the plant well before we’ve put that fungicide down.
If we only do one late application just prior to the snowfall, we’re missing some of the initial infection.
It can seem like a lot, but it also has some preventative impact on similar fungi. So the benefit there is you can even get some dollar spot control while you’re starting on snow mold.
What type of fungicide should LCOs use to combat snow mold?
This is a common question that I get, and unfortunately my answer is always ‘it depends.’ It depends on many things including the location, maintenance regime, expectations, and financial capacities of the homeowner.
If you care for a very high-quality lawn that receives significant snowfall and is well-fertilized with nitrogen going into winter, then a strong fungicide or fungicide combination should probably be applied.
The good news on home lawns is that because Kentucky bluegrass and other lawn grasses are more resistant to snow mold infection than creeping bentgrass, usually only a single active ingredient is required for excellent snow mold protection.
There are several active ingredients effective against snow mold, including but not limited to azoxystrobin, propiconazole, pyraclostrobin, and triticonazole.
Lawn care operators can check with local extension educators or peruse university research trials to find an effective fungicide. Wisconsin’s snow mold reports can be viewed at bit.ly/snowmold.
What are some things to remember when preparing for snow mold?
First, limit the amount of fast-release nitrogen that is applied late in the fall. Late season nitrogen will keep turf plants lush and green and make them highly susceptible to snow mold.
Second, remove leaves or any sort of object that is going to trap moisture near the turf surface, which will increase snow mold. If a fungicide is required, do your homework and find a fungicide that will be effective and won’t bust your (or your client’s) budget. The tough thing about snow mold is that you only get one shot at it. If you mismanage in the fall, you usually can’t go out and correct things in December or January after the snow has fallen.
One important thing to remember, however, is that snow mold rarely kills turfgrass. It may look pretty bad after snowmelt, and in some cases can lead to turf death, but once turf growth resumes in spring it often recovers within a few weeks.
That’s good to remember once the snow starts to fall.
The author is a custom media editor at GIE Media.