Snow mold diseases can be challenging to manage because multiple fungi are involved that affect numerous varieties of turfgrass. Winter conditions also can vary greatly year to year making it even more challenging to manage diseases such as Typhula incarnata, Typhula ishikariensis or Microdochium nivale. Knowing which pathogen is present is critical to developing an effective management plan.
There are several traditional fungicides available that are effective for managing snow mold pathogens, as well as some non-traditional options.
Eight research trials conducted on golf courses in Utah have shown that Civitas One, alone or as part of a program, can be effective at managing various snow mold diseases while also resulting in improved turf quality and spring green up.
Civitas is an isoparaffin-based fungicide from Suncor via Petro Canada that promotes induced systemic resistance properties in plants. Induced systemic resistance is a physiological plant response in which environmental, chemical or biological activators trigger plant-defense mechanisms. This primes defense genes to respond rapidly to pathogen attack by producing defense proteins and other chemicals. Civitas, however, does not provide fungitoxic effects, or kill the fungus directly like many other fungicides. Instead, it has fungistatic properties that inhibit the growth and development of some fungi.
Suncor's Civitas One formulation is a premixed version of Civitas and the Civitas Harmonizer pigment.
Most of the Utah research has been one-off trials - not replicated over years - so the bulk of the information here is from 2012 when identical trials were conducted simultaneously at two different golf courses. The fungicide programs were applied in October or November before expected snow cover, with no follow-up applications in spring after snow melted. Replicated plots on putting greens consisting of creeping bentgrass, or mixes of creeping bentgrass with annual bluegrass were used.
Because of its systemic mode of action, Civitas should be applied while turf is still actively growing, which can be two-three weeks earlier than traditional contact fungicides. Multiple applications also are recommended, made as two split-applications, so traditional fungicides have been mixed with Civitas at the second application.
Once snow melted in spring, damage from snow molds was assessed on a damage scale of 0 percent to 100 percent. Damage means were used to calculate percent control when comparing to the damage in untreated turf. Turf quality and green up also were rated in spring on visual 1-9 scales in which 6 is the lowest acceptable quality. Leaf chlorophyll index also was measured with a chlorophyll meter in spring, and phytotoxicity was also noted.
The research showed that gray snow mold (T. incarnata) affected 36 percent of untreated turf in Salt Lake City in 2012. The standalone programs of Civitas (with harmonizer) applied either once, or as two split-applications before snow cover, provided control levels of 63 percent-67 percent of T. incarnata under fewer than 75 days of snow cover.
The same Civitas programs did not perform well in higher elevations where snow cover lasted 100 days, providing just 5 percent-7 percent control of speckled snow mold (T. ishikariensis). Gray snow mold is usually more common in areas with shorter snow cover duration and higher mean temperatures than T. ishikariensis.
Similar work from Wisconsin mirrored these results. It is not clear why the induced resistance provided by Civitas lacks efficacy under extended snow cover. Perhaps speckled snow mold is not as sensitive to Civitas, or the plant's ISR just gets overwhelmed under extended snow cover. It is clear that more research is needed. What is clear is that Civitas in concert with other fungicides improves control of snow molds.
When Civitas alone was not effective, a program that included Syngenta's Instrata in the second application provided almost complete control of speckled snow mold. The Wisconsin research showed that the addition of other traditional fungicides, such as chlorothalonil, triticonazole, tebuconazole, vinclozolin, iprodione and propiconazole to Civitas programs at standard rates provided acceptable control under moderate snow cover, but some mixtures broke down after 170 days of snow cover.
Research in New York has shown that similar control of gray snow mold can be achieved with Civitas and reduced rates of Instrata (chlorothalonil, propiconazole and fludioxonil), whereas acceptable control was achieved in 2012 in Utah with Instrata alone at 5.5 ounces per 1,000 square feet. Other years have shown that higher rates of Instrata in concert with Civitas failed to provide sufficient control, illustrating that climate conditions year to year play can be a factor as well.
The historical duration of snow cover at each respective course probably will dictate the rate of Civitas, if any, that is needed to achieve acceptable control. The highest label rate usually is a good idea where snow cover duration is long.
Fungicide programs that include Civitas have revealed other benefits, as well. Leaf injury from DMI fungicides, and leaf residues from other contact fungicides commonly seen as snow melts have been masked. Turf treated with Civitas plus Instrata exhibited better turf quality and greenup in spring compared with either product alone. Earlier greenup and growth of turf in spring can be a desirable response if some snow mold damage has occurred.
Even Civitas programs that have not controlled snow molds have provided better recovery in spring when soils warm. Responses like this have also been reported in Wisconsin, New York and Massachusetts. It also has shown positive results for preventive control of pink snow mold in research conducted in Oregon and Washington.
Although more research is needed, Civitas is not a silver bullet for controlling snow molds, but can be a beneficial component to a sound snow mold program with multiple chemistries. In areas where extended snow cover is expected, Civitas alone will not provide adequate protection and must be tank mixed with other fungicides. Specific tank mix partners and rates will depend on the pathogens that are present and length of snow cover. Based on the work in Utah, the best programs have included two sequential applications, where Civitas is applied alone, or mixed with a DMI for the first spray (on actively growing turf), then then followed approximately two-weeks later with Civitas mixed with a DMI, or contact fungicide, or both.
Adam Van Dyke is the founder of Professional Turfgrass Solutions, a Salt Lake City-based turfgrass consulting firm.