It is really nice to experience a warm-up in Mid-February, but we know that it is a likely a cruel trick from mother nature. NBC 15 in Madison just said that Monday could yield 5 to 10 inches of snow, if all the expected precipitation is snow. Yet, today temperatures exceeded 40 degrees in Southern Wisconsin and is expected to exceed 50 degrees tomorrow! Its funny that I get excited about 50 degrees, when I was in North Carolina I considered that cold. As the warm-up continues, the snow will be melting and gray snow mold and Microdochium patch may show their ugly heads. If fungicides were applied last fall, then I would not expect too much damage. However some areas south of I-80 may not have made preventative applications. I know many down in Missouri, Arkansas, and maybe even Kansas did not make preventative applications. Based on the duration of snow cover in those areas, gray snow mold will most likely not be a problem. Microdochium patch however may be a problem.
The question arises, should I spray when the snow melts? To determine if an application is warranted there are two things to consider: 1) Is the fungus causing new infections? 2) Is the ground saturated? When the snow melts Microdochium patch symptoms maybe apparent and severe, but if environmental conditions are not conducive the pathogen will not continue to spread. Microdochium patch will continue to develop when temperatures remain below 68F with high humidity, intense cloud cover, or both. Symptoms immediately after snow melt usually have the “classic look” with a pink or orange tint. An image of these symptoms are at the upper right hand side of this post. If environmental conditions are conducive for Microdochium patch development in the absence of snow, symptoms will have a water-soaked appearance with center gradually turning a light brown. An image of those symptoms are below. If there are any questions about the activity of the fungus send a sample to a diagnostic lab.
Another factor to consider is how saturated the soil is. Applications of any material to saturated ground should be avoided entirely. Failing to do so could result in loss of the material to runoff. Another consideration is running equipment over saturated ground will likely do more damage than the fungus will.
If conditions become conducive for Microdochium patch development, there are fungicides that will halt its development. Fungicides with the active ingredients iprodione, vincozolin, thiophanate methyl, trifloxystrobin, azoxystrobin, pyraclostrobin, fludioxonil, and chlorothalonil are effective against Microdochium patch. Normally it is hard to beat the dicarboximides and thiophanate methyl for Microdochium patch control, but there are other options that maybe more relevant in your area. Chlorothalonil does not perform all that well by itself, but it is a good tank mix partner with any of these other products.
On another note, after receiving much ridicule from Dr. Kennelly and the Packer Nation that surrounds me about the tragic loss the Bears were handed by the Packers, I am looking forward to baseball Spring training. Like I say every year, as all Cubs fans do, this is the year to break the Billy Goat curse!