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Bacterial Stalk Rot in Corn

07/16/2018
Bacterial Stalk Rot in Corn
  • Bacterial stalk rot of corn is favored under conditions of high air temperatures and wet weather or high humidity.
  • Bacterial stalk rot is not common but often shows up with overhead irrigation of corn, especially where the water source is a lake, pond, or slow-moving stream.
  • Leaf or stalk injury from hail, insects, or mechanical injury facilitates bacterial infection. Infection may be worse next to irrigation pivot wheel tracks.
  • Several bacteria species can cause bacterial stalk rot.
  • There are no rescue treatments for bacterial stalk rot.

Introduction:

Bacterial stalk rot of corn is a somewhat unusual disease of corn. Several seasons may pass without the disease showing up at all. Then, localized outbreaks of the disease can occur. This disease is most common with overhead irrigation where the water source is a lake, pond, or slow-moving stream. Leaf and stalk injury encourages entry of bacteria into the corn plant. This injury can result from insect feeding (especially from boring insects), hail, or mechanical injury. Passage of towers of center pivot irrigation systems can tear corn leaves, injure stalks, and transfer mud onto the corn plant, inoculating the plant with bacteria. Flooding of corn has been occasionally associated with bacterial stalk rot infection of lower nodes of corn plants.

Disease Profile and Description:

Several species of bacteria are capable of causing bacterial stalk rot. One of the more common species associated with this disease is Erwinia chrysanthemi pv. zeae. The infectious bacteria reside on crop residue and the soil surface, but may also contaminate lakes, ponds, and slow-moving streams. This is why bacterial stalk rot infections are often associated with overhead irrigation. When these water sources supply the irrigation system, the irrigation creates an ideal environment for infection and, at the same time, provides the inoculum source.

Further, bacterial stalk rot infections can occur when storms splash mud onto corn plants, particularly if wind or hail also damages corn leaf or stalk tissue. Insect damage can encourage bacterial infection of corn. This is especially true with stalk borers, European corn borers, or other insects that tunnel into the corn plant. Infectious bacteria likely enter the plant through leaf stomates, as well.

Early symptoms of bacterial stalk rot infection often include a pale or tan-colored discoloration of the corn leaf sheath and stalk at a node. (This should not be confused with symptoms of “purple sheath,” a benign fungal infection of the leaf sheath.) The bacteria typically enter the stalk at the nodes and infection takes over the stalk, moving up and down in the vascular tissue. The entire plant can be infected, including developing corn ears.

As the disease progresses, sections of the corn stalk turn tan or brown and mushy. Leaves may become infected and the entire, upper part of the infected corn plant can collapse with severe infection. Localized infections sometimes develop at lower nodes, resulting in pinching and collapse of the stalk at the point of infection. Bacterial stalk rot infection features a sour or foul odor. Along with the mushy or slimy rot, this is partially diagnostic for the disease.

Managing Bacterial Stalk Rot:

There are no rescue treatments for bacterial stalk rot. Management primarily includes destruction of crop residue with tillage and avoiding use of contaminated water supply for overhead irrigation. Crop rotation is likely to help with avoidance of this disease. Some corn hybrids appear to be somewhat resistant to bacterial stalk rot, although this disease occurs so infrequently as to make this a low priority management method.


STALK ROT 2.jpg

Image 1: APSnet.org

Image 2: Forestryimages.org


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