Tar spot was a big issue for growers in south-central Michigan in 2021, and agronomists were bracing for a repeat in soybean fields that farmers rotated out for corn.
However, drought has actually helped keep it at bay this year.
Missy Bauer, an agronomist with Farm Journal, says that when the average humidity is above 75%, crops become at risk.
In 2022, Purdue University found tar spot in corn is primarily fueled by cool conditions around 60-70 degrees. When relative humidity is at or above 75% and when leaf wetness lasts for more than seven hours.
Experts remind growers of apps like Tar-Spotter which can help determine if local weather conditions are putting crops at risk.
