Early symptoms of tar spot.

An increasing concern for many is the spread of tar spot across the Midwest. This disease has significantly impacted corn yield since its first appearance in 2015. The Crop Protection Network recently reported that tar spot has been found in 10 states, with some areas experiencing yield losses of 20 to 60 bu/A.

Since tar spot is a relatively new disease, it’s important to learn its signs and symptoms, and be ready to take necessary action to prevent yield loss.

According to Purdue Extension researchers, you should be especially mindful of these environmental conditions:

• Cool temperatures between 59-70°.
• Conditions with 85% relative humidity.
• More than 5 hours of leaf wetness.
• Wind-driven rain and storms.

If environmental conditions are right, be on the lookout for these symptoms:

• Small, raised black spots that are circular to oval in shape.
• Tan or brown halo surrounding the spots, which may appear on both sides of the leaves, leaf sheaths and husk.

Tar spot has a latent period of up to 14 days, so your corn may be infected before you see these symptoms. Since this disease is difficult to control curatively, a preventive fungicide application is recommended.

To stay a step ahead of tar spot and other key diseases, we recommend 2 powerful fungicide products: Miravis® Neo and Trivapro®. Powered by Adepidyn® technology, Miravis Neo sets a new standard in its class for broad-spectrum disease control to help your crops produce more bushels more often. The 3 active ingredients in Trivapro provide long-lasting preventive and curative disease control and plant-health benefits to maximize yield potential.

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