Goss's Bacterial Wilt and Leaf Blight
This disease was first confirmed in Minnesota in 2009 and in Indiana in 2008. Although it may have occurred earlier in these states, it appears to be a spreading problem. Yield losses from Goss's bacterial wilt and blight can be significant on susceptible hybrids. Symptoms can vary on different corn inbreds or hybrids, and can be confused with Stewart's wilt where this disease occurs.
The primary symptoms on leaves consist of large tan to gray linear lesions with irregular margins extending parallel to the veins, and large sections of leaf area can be affected. Irregular dark green to black, water-soaked spots ("freckles') that develop in the lesions distinguish this disease from Stewart's wilt. Shiny patches of dried bacterial ooze (exudates) is often present on the lesions. Fungal structures do not develop in the lesions. In plants with systemic stalk infections, orange vascular bundles may be seen in the stalk. The seedling blight phase of this disease may cause wilting and death of seedlings, but is not common.
Conditions and Timing that Favor Disease:
The disease infects plants that have been wounded, often by hail, sand-blasting, rain, wind, or machinery. Development of Goss's bacterial wilt and blight is favored by warm and humid conditions. Symptoms are often most severe at or soon after silking.
This disease is caused by the bacterial pathogen called Clavibacter michiganensis subsp. nebraskensis. It overwinters in infested corn debris near the soil surface. The disease can also be seed transmitted. Some grasses are also susceptible, such as green foxtail, shattercane, and barnard grass.
This disease is managed by using resistant hybrids, rotating crops, deep tilling after harvest, and by controlling grassy weeds.