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Goss’s Bacterial Wilt and Blight Developing

While out scouting corn fields (the week of August 11, 2020) Goss’s bacterial wilt and blight (Figure 1) was found starting to develop in a number of fields. In South Dakota we have seen a re-emergence of Goss’s wilt over the last ten years. Yield losses range from minimal to exceeding 50%. Goss’s bacterial wilt and blight is caused by a bacterial pathogen, Clavibacter michiganensis subspecies nebraskensis. Goss’s bacterial wilt and blight is a two-phase disease. We often observe the blight phase of the disease here in South Dakota but if the corn seedlings get infected early with the bacteria, we can observe the wilt phase of the disease as well.
 

Tan-gray Goss’s bacterial blight lesions were observed in scouted corn fields.
Figure 1. Goss’s bacterial blight was observed starting to develop in some corn fields scouted.

How It’s Spread

The Goss’s bacterial blight inoculum comes from infested corn residues (roots, stems, leaves) and from several other hosts including grain sorghum, green foxtail, barnyard grass, shattercane, large crabgrass, and others. Goss’s bacteria spread is through rain splash but can also be carried by high winds for a short distance. The bacteria enter any part of the corn plant through wounds and natural openings. Infection is favored by rainy weather especially where high winds, hail and sand blasting occur. Hot and dry weather conditions slow infection and the progress of the disease.

Symptoms

Infected leaves have long, tan-gray lesions with wavy margins along the edges of the corn leaf blade or in the center of the leaf with a water-soaked appearance. These lesions can coalesce forming larger lesions. Easily identifiable dark green to black spots (freckles) are found within the margin of the lesion (Figure 2). When these “freckles” are observed against the light, transparent spots can be seen. A bacterial exudate (ooze) is often seen on top of the bacterial lesion. A systemic wilt can also take place and move within the vascular system of the corn plant.

Tan-gray water soaked bacterial lesion with the dark green/black spots (freckles) within the lesion along the edge of the corn leaf.
Figure 2. Goss’s bacterial blight showing the water-soaked tan-gray lesion with dark green/black freckles.

Management

  •  Plant corn hybrids with resistance to Goss’s wilt.
  • Practice crop rotation. Rotation should be between broadleaf crops and small grains other than sorghum since sorghum is a host for Goss’s wilt.
  • For fields with a history of Goss’s wilt and leaf blight, tillage practices (where practical) that bury the corn stalks may speed up decomposition therefore reducing inoculum level.

Related Topics

Corn Diseases