Goss' bacterial wilt

Goss' bacterial wilt is caused by the bacterium ''Clavibacter michiganense ssp. nebraskensis''. Several strains of the pathogen are known to exist. It was first discovered on corn in two south central Nebraska counties in 1969.

Symptoms
This disease can have two distinct phases: a leaf blight phase and a systemic wilt phase. Although the full name of the disease (Goss' bacterial wilt and leaf blight) includes both phases. Leaf blight is the most commonly observed symptom, but is easily confused with other diseases and abiotic disorders. Corn plants with Goss' wilt exhibit long, large, tan lesions in the centers or on the edges of leaf blades. The margins of these lesions may have a water-soaked appearance. Black flecks (“freckles”) can be observed within the lesions. These flecks can be large and cannot be rubbed off plant tissue. If symptomatic leaves are observed early in the morning or after a rain, one can observe a bacterial ooze, or exudate, on lesion surfaces. Dried bacterial exudate is shiny, especially when observing leaves in direct sunlight. When it’s dry, Goss' wilt symptoms are easily confused with drought stress or leaf scorch from chemical burn. Leaf blight symptoms can also be misidentified as nutrient deficiency, chemical injury, Stewart's wilt (caused by a different bacterial organism), or northern corn leaf blight. In the systemic wilt phase of the disease, infected plants may exhibit drought stress symptoms and wilt or die prematurely. To correctly identify this phase of the disease, examine the vascular tissue of the stalk — infected tissue will have orange to brown discoloration. The discoloration is caused by bacteria moving within the plant’s xylem tissue.

Prevention
Rotating out of corn production for one year will allow residue to break down and reduce bacteria populations. Tillage and other practices that encourage residue decomposition will also reduce the amount of bacteria present to infect the following corn crop. Practice good weed management techniques to control grass weed species that can serve as a source of the disease.

Resistant hybrids are also available.