PCNB Watch 2010-More Suggestions and Timing Issues

In response to the stop sale order against PCNB, the UW Turf Pathology Program sent out suggestions for alternatives to PCNB. These alternatives were designed to meet the needs of golf course superintendents that traditionally relied on PCNB in their snow mold programs. Most of the suggestions we put forth included mixing a contact fungicide (i.e. chlorothalonil or Medallion) with a localized penetrant (iprodione), and/or acropetal penentrant (thiophanate methyl or a DMI fungicide). Our basis for putting together these suggestions were to help golf course superintendents find a substitute for PCNB quickly. Typically we do not make such specific suggestions, but we felt more specific suggestions were warranted under the circumstances. By no means are these suggestions all inclusive, there a multitude of options when considering snow mold programs. We simply narrowed the focus a bit based on data from snow mold trials dating back to 2001.

A few points to keep in mind, PCNB is a contact fungicide and had decent activity against all three snow mold pathogens. However we consistently heard about many breakthroughs when PCNB was the sole fungicide used for snow mold. The strengths of PCNB were cost and ease of use. There was very little thinking involved when using PCNB because it was fairly effective and could be applied relatively early, late or both. By losing PCNB this year, now the game has changed slightly because we are incorporating systemic fungicides with contact fungicides. Therefore it is imperative to have the systemic fungicides down before the plant goes dormant (metabolic activity stops). Unfortunately I do not have specific answers on when dormancy occurs, but I do think that most golf course superintendents know when dormancy occurs.

Another question that has come up is how many applications should I make? In our trials the vast majority of our applications are made just once late in the season. For example, at Wawonowin the final applications are typically applied just before Halloween. This was a problem at Wawonowin in 2009 and 2010 because the first snowfall came much later than normal. Thus some mixtures failed that typically have performed well under this intense snow mold pressure. At Sentryworld, final applications in our trials are typically applied the week before Thanksgiving and we observe excellent snow mold suppression. Basically stick to what you've done in the past with regard to the number of applications. Just be sure that the systemic fungicides are deployed before the plant goes dormant. To help clarify questions about timing and number of applications, we are initiating a timing and application study this fall. I will present our initial results from this study in Spring 2011, so stay tuned!

Finally when selecting an alternative to PCNB, take into account what your golf course expectations are. There is no need to try to achieve perfection if that was not the goal in previous years. I have inserted a few graphs to illustrate differences among treatments at Sentryworld Golf Course in Stevens Point, WI in 2009-2010. The goal is to find a program that meets the expectations of membership or golfer without overextending the budget even more. I have included a link to our snow mold trials once again, just in case you want to look over more data before making a decision. Be sure to check out the images in order to see what 20 to 30 % disease looks like in our trials. I also encourage everyone to sit down with your local fungicide sales representative before making a decision because there is a lot options with regard to pricing of different active ingredients.


If you want more information on snow mold and alternatives to PCNB, please tune in to the Bayer Back to Basics Webinar Series on September 21 or come to the iTurfExpo (Midwest Golf House, Lemont, IL) on September 22.