By Emmanuel Byamukama
Goss’s bacterial blight was found in a few corn fields scouted the week of August 5, 2019 (Figure 1). The severity ranged from low to moderate, where at least 25 percent of the leaf area was killed by the bacteria infection on several plants.
Figure 1. A corn field with several plants showing Goss’s bacterial blight symptoms.
The disease is characterized by long, tan-gray lesions with wavy margins found in the center of the leaf or along the edges of the corn leaf blade (Figure 2).
Disease Causes
Goss’s bacterial blight is caused by a bacterial pathogen, Clavibacter michiganensis subspecies nebraskensis.
Figure 2. A close-up of Goss’s bacterial blight symptoms on corn leaf showing dark water-soaked spots (freckles).
A closer look at the lesions reveal dark green to black, discontinuous, water soaked spots (freckles) in the margin of the lesion (Figure 2). These lesions can coalesce forming larger lesions. When these “freckles” are observed against the light, transparent spots can be seen. When the bacteria infects seedlings early in the season, Goss’s wilt results.
The Goss’s bacterial blight inoculum comes from infested corn residues (roots, stems, leaves) and also 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 considerable distance. The bacteria enters 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.
Management Strategy
- 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.