06/03/2026
Frequent rain and cooler-than-normal temperatures this spring are creating ideal conditions for tar spot in Missouri cornfields.
The disease has shown up in June in recent years and is expected again in 2026, so early scouting and continued monitoring are key.
Tar spot, caused by a fungus that survives in crop residue, appears as small, raised black spots on leaves and can spread quickly under favorable conditions. While it can impact yield, MU Extension plant pathologists say there’s no need to panic.
Finding the disease in June doesn't automatically mean a fungicide application is needed. Continue monitoring how quickly it spreads, where symptoms are appearing in the canopy, disease severity and upcoming weather conditions before making management decisions.
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