Another Good Winter for Snow Mold

As Megan mentioned we got hammered with snow last week. The total snowfall amounts vary but we received over 15 inches of snow! Yes it took me most of the day on Wednesday to clear my driveway, but a wonderful neighbor used his bobcat to clear "plow trash" at the end of my driveway. The picture was taken last Wednesday morning and I was clearing a path for my dog to use the restroom. Following the snowfall, temperatures plummeted! The high last Thursday was 7 and the low was -4, so I think the snow is going to stick around a while.

With the amount of snowfall we received last week that fell on unfrozen ground, it appears that this winter is going to be conducive for gray snow mold development. Gray snow mold is induced by two Typhula species- T. incarnata and T. ishikariensis. Other names for the disease are Typhula blight and speckled snow mold. All cool-season turfgrasses are affected by gray snow mold, but the degree of severity differs with turfgrass species and the length of snow cover. Persistent snow cover provides an ideal environment for the gray snow mold pathogens to thrive and infect turfgrasses. If snow cover persists for more than 60 days than gray snow mold is likely to be problematic. When snow cover persists for more than 90 days, gray snow mold is often very severe. It is important to have an idea of how long snow persists in your location to develop a successful gray snow mold management program. Fungicides that are efficacious in areas with low to moderate snowfall may not be effective in areas with high snowfall amounts. I know I have posted our snow mold trials before, but it never hurts to repeat things. The reports clearly state how much snowfall was recorded at testing location. So pick the most appropriate site based on your conditions and hopefully you can find a chemical or mixture of chemicals that work for your budget.

What happens if we experience a winter thaw do I need to reapply fungicides? This is a question we routinely get, however I have yet to experience a winter thaw. I know I have only been here for one winter, still the last couple of winters have been fairly harsh. It is frivolous to apply fungicides when the ground is frozen, so that is the first thing to check. If the ground is not frozen then the answer is maybe. We are working with commercially available ELISA (enzyme-linked immunosorbant assay) kits to determine how long chlorothalonil and iprodione persist under snow cover and in the absence of snow cover. This technology is used to determine fungicide concentration in fleshy fruits like apples. We have just received some new data that demonstrates that our extraction method works very well and we are eagerly working on collecting degradation data this winter. Along with determining how these fungicide degrade, we are performing inoculations in the growth chamber to figure out when we lose protection to Microdochium nivale. There is more to come with this research so please stay tuned!

One interesting side note we learned from this project is the actual concentrations of the pesticides in the bottle/tank and what is detected on the plant. For example, Daconil Weatherstik is 54% chlorothalonil, when mixed in 2 gallons of water per 1000 sq ft the concentration of the solution drops to about 16 %. Then once the chemical is applied and allowed to dry for one hour we can detect about 600 parts per million on and within the leaf. I don't know if anyone else thinks those are interesting numbers, but I sure did. This spring we are going to repeat this experiment and we plan to include a sample to test fungicide concentration directly from the nozzle.

Best wishes for a happy holiday season and a happy new year to all of our readers! I am heading to North Carolina this Saturday for the holidays, so this will likely be my last post for the year. Thanks to all of the readers and thanks to John for putting the blog together!

Jim