Plant pathologist says weather is right for Tar Spot

A University of Wisconsin crops expert says their tool for predicting corn Tar Spot shows the risk of developing the disease is high right now. Dr. Damon Smith tells Brownfield, “It’s showing that the risk of finding Tar Spot is pretty high, and with that’s saying is the weather has been abnormally wet and humid, and up until the last week or so, we’ve had temperatures kind of on a cooler side or cooler than normal.”

Smith says he’s scouting corn in the V6 to V8 growth stage in southern Wisconsin now.  He says he hasn’t found tar spot yet, but the conditions are right for it. “The heat is good. The Tar Spot fungus doesn’t really like it real hot, but I would really like to see the weather kind of dry out a little.”

Smith says his colleagues in Illinois are also scouting for corn diseases. “We’ve got some common rust which is, as the name suggests, very common although it is a little earlier in the season but we’re kind of keeping an eye on what’s going on there. There’s been some Northern Corn Leaf Blight down in Illinois. We haven’t seen any of that here yet.”

Smith advises farmers to scout fields now more than ever and look closely at the lower leaves. “Those lower leaves aren’t going to contribute to yield, but they’re good indicator leaves for what diseases are out there so that you can make an informed decision later on at the critical time to get that fungicide application on.”

Smith’s University of Wisconsin team has developed a free smartphone app for predicting white mold in soybeans and are testing a similar program for predicting tar spot this summer with hopes of releasing the tool to the public next year.