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Tar spot detected in central Iowa

Tar spot has been confirmed in a central Iowa corn field.

Iowa State University Extension plant pathologist Dr. Alison Robertson says the detection in Poweshiek County is not surprising because the crop disease has been observed in June the past three years.

North central Iowa farmer April Hemmes tells Brownfield tar spot is a problem in her area.

“But it hits later, so it doesn’t really effect the yield that much. But I’m not going to take a chance, I will spray fungicide.”

She says a proactive treatment seems to provide a positive return even when margins are tight.

“Just one of those (where) you close your eyes and write the check I’ve found out. One year I did it and it made an almost 15 bushel-an-acre difference, so that pays for itself pretty quick.”

Robertson suggests weather is the most important factor with tar spot, saying temperatures in the mid 60’s to mid 70’s with relative humidity of less than 90 percent favor the disease.