News

Heat slows tar spot, but corn farmers encouraged to keep scouting

A plant pathologist with University of Missouri Extension says tar spot has been confirmed in Missouri and other states this year, but the heat has been slowing its development.

Mandy Bish tells Brownfield that doesn’t mean farmers should stop scouting for the disease, because the pathogen is still present.

“It’s like us, we move slow in hot weather,” she says. “If we were to get a string of cooler temperatures, 64 to 73 degrees in 24 hours, then we should expect it to start picking back up again.”

Tar spot was confirmed last month in Ray, Lafayette, Saline and Cooper Counties in Missouri. Bish says they are low incidences and not near the ear leaf. “We’re talking one or two lesions on a couple of plants in the field.”

She says farmers should avoid fungicide applications until tar spot threatens ear leaf in the optimal fungicide application window.

“That window that we want to protect the ear leaf is from tasseling all the way to R3 or the milk stage. We don’t want to go too early out of panic and then the residual wear off and cooler temperatures come in. That would be a worst case scenario.”

The Crop Protection Network says tar spot has been confirmed in Missouri, Minnesota, Iowa, Illinois, Nebraska, Kansas and Indiana this year.

Brownfield interviewed Bish at MU’s Crop and Pest Management Field Day on Wednesday.