Snow Problem

Combating snow mold without PCNB

Published in the December 2011 Issue Published online: Dec 01, 2011 Henry C. Wetzell III, Ph.D.

On August 12, 2010, the EPA issued a stop sale on for­mulated pesticide products containing the active ingredient pentachloronitrobenzene (PCNB) to the American Vanguard Corporation (AMVAC). This was a serious concern to turf managers, as PCNB has been a standard, economical control measure for snow mold since the 1960s. Thus, crop protection companies wanted to evaluate fungicide products within their portfolios to see if they could provide an alternative to PCNB under the environmental conditions of the Pacific Northwest (PNW).

The primary turf disease the PNW encounters is Microdochium patch, which is caused by the fungus Microdochium nivale. The disease usually starts in the fall as temperatures cool, overcast conditions persist and rain show­ers become more regular. The disease continues to develop through the winter with or without snowfall and is why this disease is also called pink snow mold. The disease thrives under PNW winters where typically snow comes, melts off and comes back again. This cycle tends to happen repeatedly into the early spring. Typical symptoms of pink snow mold shortly after snow melt are shown in Figure 1. Microdochium patch can continue to be active into the late spring, early summer if temperatures remain cool and rainfall persists.

For the winters where we experience persistent snow cover, gray snow mold can also be problematic. Typhula incarnate and T. ishikariensis are the fungi that incite gray snow mold. Gray snow mold caused by T. ishikariensis typically requires 100 con­secutive days to cause significant disease in turf. These fungi are identified by their formation of sclerotia, which are typically visible at snow melt. Sclerotia are survival structures for the fungus. In this case, the fungus can over-summer, germinate as mycelium in the fall and cause infections in the turf, which leads to symptoms in the early spring. Figures 2 and 3 show the sclerotia characteristics of T. incarnate and T. ishikariensis, respectively.

The objective of this trial work was to evaluate candidate fungicides and compare their performance to PCNB in manag­ing snow mold in the PNW. Three locations were chosen in northern Idaho: Avondale Golf Club, Hayden Lake; Coeur d’ Alene Resort Golf Course, Coeur d’ Alene; and Gozzer Ranch Golf & Lake Club, Harrison. All trial work was conducted on fairway height turfgrass. The results should be applicable to tee height turfgrass as well. With the exception of several treatments, the target application date was as close to the first significant snowfall as possible. All treatments were replicated four times at each location. All sprayable treatments were applied with a CO2- pressurized backpack sprayer equipped with four TeeJet 8006 flat fan nozzles, calibrated to deliver 2.0 gallon spray solution/1,000 square feet. Granular treatments were applied with a Mason jar with holes drilled in the lid. Treatments providing 5 percent or less plot area colonized by snow mold symptoms would be considered commercially acceptable control for a golf course fairway or tee.


Results

The location in the figures referring to fairway height “PLS” creeping bentgrass is Gozzer Ranch Golf and Lake Club. Microdochium patch was present at a low level when treatments were initiated. The first significant snowfall came on November 20, and over the course of the winter the snow would melt, turf would be exposed and then another snowfall would come in. This type of weather pattern occurred until early spring, with a very wet spring as well.

The location in Figure 5 referring to fairway height annual bluegrass is Avondale Golf Club. There was no active dis­ease when the trial was initiated. The first snowfall came on November 20, but the plots remained covered until late March 2011, providing about 120 days of snow cover. Microdochium patch was the only disease at Gozzer Ranch Golf and Lake Club, whereas at Avondale Golf Club, gray snow mold was also detected. However, the fungicides provided outstanding control of gray snow mold and all that was visible to rate was Microdochium patch. In other words, gray snow mold was only detected in the untreated plots at Avondale Golf Club. BASF

The results of BASF fungicides are shown in Figures 4 and 5. All rates are abbreviated in either ounces (oz), fluid ounces (fl oz) or pounds (lb) per 1,000 sq ft. Insignia SC (0.7 fl oz) + Revolution (6.0 fl oz) followed by Trinity (1.0 fl oz), Honor (1.1 oz) + Revolution (6.0 fl oz), BAS 673 00F (3.0 lb) and Trinity (1.0 fl oz), followed by Insignia SC (0.7 fl oz) + Revolution (6.0 fl oz) provided statistically similar disease control by not as good as the control provided by Turfcide (12 fl oz) at the Gozzer Ranch location (Fig. 4).

However, these same BASF treatments (note that the sequential applications were not made), which were applied early at the Avondale G.C. location, provided excellent dis­ease control (Fig. 5). The trend among both locations was that the early application of Insignia SC provided better dis­ease control when compared to Trinity.


Bayer

The results of Bayer fungicides are shown in Figure 6. With the exception of Triton (0.6 fl oz) + Chipco 26 GT (4.0 fl oz), all Bayer treatments provided good to excel­lent Microdochium patch control, which was comparable to Turfcide (12 fl oz) at the Gozzer Ranch location. Two treatments stood out, providing outstanding control, which were Interface (7.0 fl oz) and Interface (3.0 fl oz) + Tartan (1.0 fl oz).


Syngenta

The results of Syngenta fungicides are shown in Figures 7 and 8. There was not a significant difference in snow mold control between the two rates of Concert II (5.0 or 8.5 fl oz) applied. Both rates provided good disease control at the Gozzer Ranch location. Adding additional Banner Maxx to Concert II improved disease control to excellent, which was comparable to Turfcide (12 fl oz) (Fig. 7). There was not a significant difference in snow mold control between the two rates of Instrata (5.0 or 9.0 fl oz) applied. Both rates provided excellent disease control at the Gozzer Ranch location, which was comparable to Turfcide (12 fl oz) (Fig. 8). Renown (4.5 fl oz) and Headway G (4.0 lb) also provided excellent snow mold control that was comparable to Turfcide (12 fl oz).

In summary, these trials demonstrated that there are other fungicide products that provide excellent snow mold control with the absence of PCNB from the marketplace. This trial work also demonstrated that the mindset of mak­ing your snow mold fungicide application as close to the first anticipated significant snowfall as possible may not provide the best performance from your fungicide. Scout in the fall for the first signs of Microdochium patch. Initial symptoms may be the best time for your snow mold application. This season’s trial work will focus on moving application timings forward and determining their effects on snow mold control. Hopefully, Mother Nature does not move her clock forward as well.