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Tar spot confirmed in Missouri

A plant pathologist with the University of Missouri Extension says tar spot has been confirmed in northwest Missouri.

“Now that the fungus is here to stay, it’s always going to be a question of are the conditions favorable?”

Mandy Bish tells Brownfield the spring weather conditions were favorable.

“We had cool temperatures in May and it was wet. The cool temperatures are going to favor tar spot and the moisture is the icing on the cake, essentially.”

She says the tar spot confirmed in Nodaway County is one of the earliest cases in the state.

“The corn was at the V10 growth stage, so not quite tasseling. It was low incidence and a case of really good scouting.”

Bish says the footprint for the corn disease is expanding across Missouri and farmers should be scouting for black lesions on the leaves of corn.

“In the beginning, when there are only a few lesions present, it can look like insect frass. You want to see if you can scrape it off the leaf. If you can, it would be insect frass or something else. If you can’t scrape the lesion off and if it’s starting to go through both the top and bottom of the leaf, there’s a good chance it’s tar spot.”

Fungicides can help control tar spot, but Bish says farmers should avoid applying fungicides before tar spot reaches the ear leaf.

Bish tells Brownfield she’s expecting more tar spot confirmations in Missouri the next few days.

Farmers can reach out to the MU Extension’s Plant Diagnostic Clinic to confirm tar spot.

Tar spot has been confirmed this year in Indiana, Indiana, Illinois, Kansas, Iowa and Nebraska.