Corn Disease Updates

Nathan Kleczewski, Extension Specialist – Plant Pathology;

Corn is starting to take off, and this means that the next set of diseases to keep an eye out for will be the foliar diseases. The most common diseases impacting corn are the residue-borne leaf diseases including Grey Leaf Spot and Northern Corn Leaf Blight. The use of hybrids with good/excellent resistance to these diseases is highly beneficial and often negates the need for additional disease management during the season. Hybrids with good resistance result in smaller lesions, fewer spores and therefore less disease spread, and overall healthier plants. The chance that these diseases may pose a problem for you increases with each of the following:

  1. Racehorse hybrid with low/poor resistance to common diseases (GLS and NCLB)
  2. Continuous corn
  3. No till/minimal tillage
  4. Rainy weather or heavy irrigation
  5. High plant populations

If scouting indicates that you have GLS or NCLB on either of 2 leaves below the ear leaf, then a fungicide application at VT/R1 will provide the most benefit in terms of efficacy and economic returns. This does not guarantee the fungicide application will pay, but the likelihood of it doing so will increase.

Other things to keep in mind are diseases that need to blow in such as Southern and Common Rust. We see both of these to some extent every year, but often they do not arrive until late in the season and therefore likely have a minimal impact on yield. Late planting and a wet spring in the southern states may result in us seeing elevated levels of these diseases, but only time will tell. As a result, is important to scout and pay attention to information in the WCU, Field Crop Disease Management Blog, and other regional extension resources to see if there may be a risk for these diseases. A good source of information on common and Southern rust can be found here:

Lastly, remember that a new disease, tar spot, was detected in corn from Indiana and Illinois last year, and was reported in Florida corn 2 weeks ago. We have not seen the severe form of this disease where it has been detected. However, keep your eyes peeled and contact me, your county Extension agent, or the Plant Clinic if you suspect you may have tar spot in your fields. More information on tar spot can be found here: