Black tar spot is making itself known this fall. So far, it has been confirmed in more than 30 Michigan counties, and that list could grow as harvest moves on.
“The earlier it gets going, the greater amount of damage it’s going to do,” he said. “This year we’re seeing damaging levels under irrigation. For the most part, dry land fields have been less severely impacted.”
Tar spot can have a significant impact on yield if it’s present in the plant for long. The yield losses this year might not be as bad compared to last year, but Chilvers said more should be known as harvest advances.
“Last year we were seeing 50 bushel losses—this year, I think in general the losses are going to be less,” he said.
Farmers are trying to get the crop harvested, and Chilvers still encourages scouting your fields. If you have tar spot in your field, he suggests taking note of those fields and make a plan to manage it in 2020.
“One of the big things we’re going to be looking for is lodging, whether that’s caused by tar spot or other diseases, and then trying to harvest those fields that are at greater risk to lodging,” said Chilvers.
There has been some confusion with common rust, so if you suspect you have tar spot, Chilvers recommends providing a sample to MSU for verification, and they’ll process it at no charge.