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Disease Triangle: If The Conditions Are Right...

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disease triangle white snow As it has been said many times about the Midwest, “If you don’t like the weather, wait a minute and it will change.”  In mid-December, the temperatures were below zero and there were more than 6 inches of snow on the ground. One week later, the temperatures soared to a balmy 55 degrees on Christmas night and well into the next day. As I was writing this blog, the temperatures dropped back to normal December ranges at 24° F. It is supposed to warm up to the upper 30’s as the week goes on, so we are on a roller coaster ride of fluctuating temperatures. In the past, I have written about what is required for a disease to develop also known as the Disease Triangle.

3 Points of a Disease Triangle

  1. Host plant
  2. A disease-causing organism
  3. An environment has to occur for a long enough time for the disease to develop and infect the host plant.
As I wrote earlier, on Christmas night the temperatures steadily rose to the mid 50’s by Monday morning. This meant that the snow melted quickly and that there was a good deal of moisture available from the misty rain that fell Christmas day and into the night. It was also cloudy Monday morning. All of these conditions are needed for Grey Snow Mold to develop. By mid-morning, I did see it begin to develop in my back yard. It may sound a little strange to say, but I was excited to see how quickly it developed. It stopped as quickly as it started as the sun came out, which stops the activity. So did the subsequent drop in temperatures overnight. The amount of Snow Mold that did occur may have been minor, but the fungi remains in the lawn. When conditions are in alignment, it will start up again. Then again, if the same conditions do not occur, it may not develop. One thing to remember about Snow Mold, either Grey or Pink, snow is not a requirement for it to develop. It just has to be above freezing, and cloudy with lots of available moisture to complete the third side of the Disease Triangle.