Considering Disease Resistance for Conventional Corn Seed Selection

Steve Sick

Sep 25, 2018

Many farmers are considering switching to conventional corn to save on seed costs. But when selecting seed, there are many factors that go into a conventional corn seed selection plan.

From maturity to standability, the list of measured corn characteristics is long, and any combination of them could be key to your operation in any given season. Corn hybrid diseases can rob yield quickly through the leaves, stalk or ear, so choosing hybrids that are bred with some resistance can help you protect your profits from the start.

In addition to choosing genetics that have good disease tolerance, you should consider using a fungicide when recommended.

Tracking disease history in your fields

A good rule of thumb is to keep track of diseases you’ve seen in and around your fields. Knowing what pressures you’ve dealt with before and what could remain in your fields can help you proactively choose seed that can resist the common pathogens that might pop up on your farm in-season.

Many common corn diseases can overwinter in corn residue, which makes rotation another important consideration.

Diseases to watch for in conventional corn

While the diseases that could impact your conventional corn are the same as those in traited corn, it is essential to know what to look for. Remember, too, that insect damage can create an entry point for a variety of corn diseases, so make sure you have an integrated pest management program in place to protect your conventional corn investment.

Here are some common corn diseases that you should look out for:

Leaf diseases
  • Gray leaf spot:Long, rectangular lesions; initially light tan and eventually turning gray - that are usually restricted by the leaf veins. These can grow together and eventually kill the leaves.

  • Northern leaf blight: Cigar-shaped lesions 1-6 inches long that start out a gray-green and turn grey or tan. This starts in the lower leaves

  • Goss’s wilt: Long, wet, gray-green to black lesions with wavy edges. The lesions ooze, leaving crystallized deposits on the leaf. Some plants have a slimy stalk rot and may wilt.

  • Common rust: Dark red pustules on both upper and lower leaf surfaces. This shows up in the mid- to upper-canopy

  • Southern rust: Orange pustules that cluster on the upper leaf surface. First seen in the mid to upper canopy, this disease likes hot weather and can be very aggressive

Ear rots
  • Fusarium:Shows up as a white/pink, cottony mold that usually begins with already damaged kernels. Infected kernels are usually tan, brown or white-streaked. The fungus produces mycotoxin.

  • Diplodia: Starts as a white mold beginning at the base of the ear but eventually rots the entire ear. This rot can sometimes be seen on the outside of the husk. Diplodia can also cause stalk problems that lead to lodging.

Stalk rots
  • Anthracnose: Shows up as narrow, watery lesions that grow together into large, black spots on the stalk. The inside of the stalk may also be blackened..

  • Gibberella: Noticed in dark brown streaks or black dots that can be scraped off on the lower internodes. The inside of the stalk is rotted, pink and shredded.

Treatments for various corn hybrid diseases

A complete list of chemicals labeled for these and other diseases can be found on FBN.


Please consult with an independent agronomist and consider your specific field conditions (e.g,. soil type and texture, weed pressure, and rotational factors) before making a chemical planning or purchasing decisions. You are solely responsible for complying strictly with the label and the laws in your jurisdiction and for your intended application. This information is not intended as an agronomic recommendation, nor are we making any such recommendation. Always consult an independent agronomist if you are unsure of agronomic decisions on your operation. We are not a licensed commercial or private applicator of chemicals including, without limitation, herbicide, pesticide, insecticide, rodenticide or fertilizer. The reader is solely and exclusively responsible for determining the suitability of any product for his/her intended use, following the product label for proper handling and use, and for complying with all applicable local, state, and federal law. This information is a summary of product information and should not be used as a replacement for consulting the applicable product label. Please consult the label for the most complete and up-to-date information about any referenced product. Readers must have a valid applicator or dealer license to use restricted use pesticides.

Steve Sick

Sep 25, 2018