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To Spray or Not to Spray

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!

8 Responses to “To Spray or Not to Spray”

John Kaminski said...

Jim, It will be interesting to see just what shows up after this season. It may be that it hit us hard and leaves as quickly as it came. On a side note, we had Microdochium on our research plots in Maryland in JUNE! I took a bunch of crap from a reviewer of a paper where the data was included, but luckily we had isolates and photos from the disease. It was just a cool, wet, overcast spring. Go figure.


Jim said...

It will be interesting. I don't know what the Northeast was like in the fall, but we were really dry. So snow molds may not be as severe. Who knows!

We also will see outbreaks of Microdochium in May and even into June. It all depends on the weather, hopefully the reviewer wasn't a plant pathologist. They should know better :)


Chris Hoff said...


Any thoughts or observations on how the spring thaw / melt will effect fungicide performance - especially in the absence of longer periods of no snow cover (say 14 days) followed by a significant snow event? Obviously in our region is this very possible & often the norm come March.

chris said...

At my course, we have been getting a lot of frost lately, which, is new to me coming from southern California. Our 2 and 3 greens have had a really hard time with this. Are the frost related issues similar or the same as snow related? IF they differ, what are the issues keepiong one from being the other?

Jim said...


That is a great question! We are finding with Paul Koch's PhD work that fungicides like iprodione and chlorothalonil are not as sensitive to light as we previously thought. Paul has actually done a fairly exhaustive literature review of pesticide chemistry concerning these two molecules and it appears at least iprodione is primarily degraded by microbes.

Therefore at iprodione degradation is governed by temperature. Paul also did a neat study last summer examining this and found that iprodione provided significantly longer control of dollar spot at 68 F compared to 86 F. Therefore I think fungicide performance will largely be unaffected. Does this make sense?

chris - again said...

sorry for the capital letters on the "if" and the spelling on "keeping"; should not watch Golf Channel, putt and type at the same time.

Chris Hoff said...


Yes - makes perfect sense! We are losing our snow pack rapidly in the Twin Cities, but I'm not naive enough to think it not return at some point. March & early April are always interesting times - especially if you are relying on a product applied the previous November 1st.

Jim said...


I understand and you are correct. The fungicides applied on Nov. 1 are no longer effective when we get into March and April. Paul is also finding that control last anywhere from 35 to 50 days (so far, we are still running the experiment) depending on the winter.

Times are fun in the Midwest in late winter, early spring!

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