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Tar Spot: The Up-and-Coming Midwest Disease

May 27, 2021
tar spot on corn

Early symptoms of tar spot

An increasing concern for many is the spread of tar spot, a relatively new corn disease, 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 bushels per acre.

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.

Researchers at the Purdue University Extension say you should be especially mindful of these environmental conditions:

  • Cool temperatures between 59-70°F
  • Conditions with 85% relative humidity
  • Greater 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 even see 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 Trivapro® fungicide. The 3 active ingredients in Trivapro provide long-lasting preventive disease control to help reduce yield loss from tar spot. And excellent plant-health benefits deliver strong, healthier crops, regardless of disease pressure. To find out how much more yield you could be harvesting with Trivapro, visit our Yield Calculator.

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