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Corn farmers contemplate fungicide for late developing tar spot

A corn disease has farmers wondering if it’s not too late to apply a fungicide. 

Iowa State University Extension crops pathologist Dr. Alison Robertson says she’s hearing reports of tar spot in fields that were either sprayed with a fungicide around tasseling or weren’t sprayed at all.

“Most of the crop is at R4 to R5, so that means we still have a few weeks left to spray. So the question is should we be spraying a fungicide to protect those plants and protect that yield?”

She tells Brownfield data from Purdue University shows spraying a fungicide this late makes no difference in the development of tar spot.

“So based on (that) data we do not recommend that a fungicide be sprayed after R4.”

Robertson does not anticipate a big yield hit from the late developing tar spot, but she is concerned about stalk quality going into harvest.