Social Links Search




Tar spot spreads in Missouri corn fields

Tar spot spreads in Missouri corn fields

By Blake Jackson

Corn growers in Missouri are facing a growing threat from tar spot, a yield-reducing fungal disease. This year, the disease has been confirmed in 19 counties, bringing the total affected counties to nearly half the state since the first case appeared in 2018.

While the primary infection sites so far in 2024 seem to be the lower parts of the corn plants, tar spot can spread to upper leaves, husks, and leaf sheaths in severe cases.

Unlike insect droppings (frass) which can be rubbed off, tar spot manifests as small, raised black spots that are firmly attached to the leaves.

The fungus thrives in moderate temperatures, preferring the mid-60s to low 70s Fahrenheit. It survives the winter on leftover corn residue, making crop rotation an important practice for managing the disease.

While completely resistant corn varieties haven't been identified yet, research suggests some hybrids are less susceptible. Fungicide application during the VT to R3 growth stages (when the tassel emerges to the ear is fully developed) has shown the most consistent benefit in years with high tar spot outbreaks. Applying fungicides earlier or later hasn't proven cost-effective.

A helpful tool for farmers is the Tar Spotter app ( This app considers weather data and other factors to predict tar spot risk based on a specific location. By entering their own information, farmers can get personalized predictions and determine if a fungicide application is necessary.

With tar spot on the rise, Missouri corn growers have resources and strategies available to combat this yield threat. Early detection, informed fungicide use, and crop rotation can all play a role in protecting crops.

Photo Credit: gettyimages-klosfoto

Quinoa field day - from seed to superfood Quinoa field day - from seed to superfood
MO farmers fight rising beetle threat MO farmers fight rising beetle threat

Categories: Missouri, Crops, Corn

Subscribe to newsletters

Crop News

Rural Lifestyle News

Livestock News

General News

Government & Policy News

National News

Back To Top