The late-fall timing of your snow mould fungicide application is critical to protect turf from those nasty snow mould patches when the snow peels back in the spring. But perfecting the timing of the snow mould fungicide can prove very difficult, unless you have a crystal ball and can predict exactly when the first snowfall is going to land.
That’s why it’s important to pursue an application to clean up any late-season dollar spot or fall Microdochium patch to set your turf up to go into winter clean before the snow mould fungicide application. But before we talk about that late season fungicide application, let’s do a quick primer on snow mould.
A quick refresher on snow mould
Pink and grey snow moulds can leave putting greens, tees and fairways unsightly and unplayable once spring rolls around. The diseases hit annual bluegrass and creeping bentgrass particularly hard. Fall is when the diseases start becoming active and is the optimal time to control snow mould. Snow mould thrives under snow cover and temperatures at 0-10°C, but sclerotia of the pathogens begin to germinate in the fall when air temperature is 10-18°C.
Snow mould is a persistent problem year in, year out. Microdochium patch and snow mould are caused by the same fungus, Microdochium nivale. The main difference between the two diseases is that with snow mould, the disease is occurring under snow cover. Microdochium patch is active in the fall and does not need snow cover to begin causing damage. Snow mould infections appear as patches of blighted leaves, stems and crowns. If you leave turf unprotected, you’re taking a big risk on subjecting turf to heavy snow mould damage.
As with most diseases, healthy turf is better able to fend off snow mould. Aerating turf to reduce compaction and limit thatch will help. So will spoon feeding nitrogen on greens or modest fall applications of nitrogen on higher mowed turf. The quicker you get snow off greens, tees and fairways in the spring, the better. Remove “collar dams” or anything else that limits water drainage.
Be especially careful with young, fall-seeded turf. Heavily fertilized new growth is more succulent, making it susceptible to snow mould pressure in the fall.
Timing your snow mould application is important. Research from the University of Wisconsin shows that the optimal timing of a fungicide application to protect against snow mould is within two weeks prior to snowfall.
The fungicide can start to degrade before snow arrives if you apply too early. Research has demonstrated that applying more than two weeks prior to snowfall can result in a loss in control by 40% or more.
Snow mould plan for fall 2022: “Go in clean”
Knowing that Microdochium patch and pink snow mould are so similar, a “go-in-clean” application can control the pathogen inoculum is so important prior to that crucial final application scheduled two weeks prior to snowfall.
Hitting that perfect timing can be difficult. It can take a lot of resources to spray an entire course and weather forecasts aren’t always accurate. And the whole plan can be thrown off if those clouds produce rain on the days leading into winter. A significant rainfall between the final fungicide application and snow cover might mean another application is required in order to achieve desired disease control and ensure a successful spring.
Since timing the final fungicide application can be difficult, the “go-in-clean” approach can help control the early pathogen inoculum, leaving the turf in better condition. This can limit later disease development and improve long-term control.
An early fungicide application can reduce pressure
A “go-in-clean” application of Mirage® Stressgard® or DedicateTM Stressgard® in late fall months will aid in controlling any lingering late-season dollar spot and cool-season diseases like leaf spot and Microdochium patch. This will keep the turf in a healthy condition for the snow mould season. Having a healthy turf stand will make your snow mould application focus on protecting your turf through the winter months.
After the “go-in-clean” application, you’ll still need to follow-up with a snow mould application just prior to the first snowfall. A single, well-timed application is often enough to keep turf protected from snow mould, even in high pressure areas.
DedicateTM Stressgard® contains the leading DMI chemistry of tebuconazole premixed with the QoI fungicide trifloxystrobin. This combination is blended with Stressgard Technology to deliver consistent and reliable results against snow mould fungi. The flexible label allows for a “go-in-clean” spray and season-ending application for snow mould control.
In high-pressure situations on high-quality turf such as putting greens, tank-mixing Dedicate Stressgard with fludioxonil has proven to be a winning combination to knock out snow mould.