The Purdue Plant and Pest Diagnostic Laboratory

What's Still Hot at the P&PDL for
November 9, 2009

Corn Ear and Stalk Rots

Gail Ruhl, Kiersten Wise, and Charles Woloshuk

The cool, wet growing season has favored infection and development of corn ear and stalk rots in Indiana. 

Gray and pink molds being found in Indiana cornfields

Fields with stalk rot should be scheduled for the earliest possible harvest to avoid significant lodging problems. Fields should be scouted for ear rots prior to harvest for a number of reasons:  (1) ear rot diseases can reduce yield and quality of the corn harvest; (2) some ear rot fungi may produce mycotoxins which are harmful; (3) ear rots can continue to be a problem in storage if the grain is not stored under optimum conditions.

Recognizing which stalk and ear rots are prevalent in a field is important for future management decisions. Susceptibility to these diseases differs amongst hybrids, so choosing a hybrid with a better disease tolerance score can help reduce disease risk in subsequent years. Rotation to soybean can also decrease disease since some pathogens survive in corn residue.

Diplodia Ear Rot:

Diplodia ear rot is characterized by a dense white to grayish mold that usually starts at the base of the ear and is evident growing between the kernels.  Very small, black fruiting bodies can be found scattered on husks or embedded in cob tissues and kernels.

Infected kernels are lightweight and have reduced nutritional value. Damage caused by Diplodia ear rot is usually limited to the field, but the pathogen can be a problem in storage if grain moisture is 20 percent or above. Diplodia Ear Rot (pdf file)

Gibberella Ear Rot:

A pink to red mold that usually starts at the tip of the ear is characteristic of Gibberella ear rot. This ear rot also has been detected on hail or insect damaged ears. The fungus that causes this ear rot produces several mycotoxins including DON (vomitoxin), zearalenone and T-2 toxin. Gibberella Ear Rot Bulletin (pdf file)

Fusarium Ear Rot:

Symptoms of Fusarium ear rot are a white to pink- or salmon-colored mold, which occurs anywhere on the ear or on scattered kernels. The mold may be associated with hail or insect-damaged kernels. Infected kernels are often tan or brown, or have white streaks. The fungi that cause Fusarium ear rot produce mycotoxins known as fumonisins. Moldy Grains, Mycotoxins and Feeding Problems

Gibberella Stalk Rot:

A pink to reddish discoloration of the pith of corn stalks is symptomatic of Gibberella stalk rot. No distinct lesions occur on the outside of the stalk.

Anthracnose Stalk Rot:

Black shiny lesions on the rind of the stalk are typical symptoms of anthracnose stalk rot. Internally, the pith of plants is discolored and shredded.

 

More Info:

Corn Ear Molds and Stalk Rot - Penn State University

Moldy corn could cause more problems if not stored properly - Purdue AgAnswers

Before feeding grain to livestock, beware of ear rots - Purdue AgAnswers

Laboratories for Mycotoxin Analyses (pdf file) - Univ of Kentucky

Risk Management Agency - Click on Mycotoxin (Jul 15, 2009) and Aflatoxin Testing Facilities (Sep 2005) at top of page

Damaged Grain Buyers List (pdf file) - As of August 2008

Corn Ear Rots Widespread in Indiana - Pest and Crop Newsletter

Gibberella Ear Rot of Corn (pdf file) Charles Woloshuk and Kiersten Wise - Includes partial list of Indiana testing labs

The Chat 'N Chew Cafe - Purdue Agronomy Dept

Fumonisin, Vomitoxin, and Other Mycotoxins in Corn Produced by Fusarium Fungi (pdf file) - Paul Vincelli, Extension Plant Pathologist, and Gary Parker, Extension Swine Specialist


Click image to enlarge

Diplodia ear rot

Figure 1. Diplodia ear rot on corn (Picture courtesy G. Shaner)

Diplodia ear rot

Figure 2. Diplodia ear rot

Gibberella ear rot

Figure 3. The pinkish mold present at the ear tip is diagnostic of Gibberella ear rot. (Picture courtesy of C. Woloshuk)

Fusarium Ear rot

Figure 4. Fusarium ear rot

Anthracnose stalk rot

Figure 5. Anthracnose stalk rot

Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service