Tar spot showing up earlier this season

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Tar spot showing up earlier this season

An agronomist is concerned about the spread and earlier detection of corn tar spot this year.

Kurt Maertens with BASF tells Brownfield because of the warm, wet weather in many areas, pockets of the corn belt are seeing tar spot now at tasseling- a time that he says is most devastating for yield if not properly treated.

“There are reports of it across areas of eastern Iowa, Wisconsin, Michigan, Indiana and Ohio right now. It is the perfect conditions to drive not only tar spot but also some of the other fungal diseases. Especially the northern half of Illinois has seen tar spot at one time or another but usually at the end of the season when it does not really matter. Where it does matter is if we see it now at tasseling and we have pockets across northern Illinois, even across central Illinois and I know some places just south of Champaign that are seeing it right now.”

He says the disease has only been in the area about five years so there are few risk management options.

“Our corn hybrids don’t have any tolerance to tar spot bred into them so really the only successful way to control it are fungicides labeled for the control of tar spot.”

He says farmers should be scouting for small black or brown dots on the leaf surface and this early you may only find a handful of lesions on the entire plant.

“As you let the disease progress you’ll continue to see more and more. Specifically, if you have stressed tissue on that corn plant, from say nutrient deficiency or insect feeding, we are going to see tar spot show up in those areas more commonly verses healthier tissue.”

Maertens says growers should apply fungicide immediately after detecting tar spot and should consider an insecticide as well since conditions are also favorable for corn root worm.

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