Tackling Goss’s Bacterial Wilt and Leaf Blight

​Goss’s bacterial wilt and leaf blight (GBW) (Clavibacter michiganensis subsp. nebraskensis) can be a major disease concern for continuous corn operations.  It is a bacterial disease, which can occur as either a vascular wilt or leaf blight.  In the field, symptoms of GBW can be easily confused with symptoms of other diseases and abiotic disorders.

The disease is of greater concern in continuous corn operations that utilize minimum tillage.  In these operations, infected residue remains on the surface and provides inoculua for the new crop.  Goss’s wilt was first identified in 1969 in western Nebraska and has since spread eastward to Indiana. 

The disease has two phases: a seedling wilt that can result in a systemic infection, and an adult-plant phase which is typically associated with leaf blight.  Although the systemic wilt is observed less frequently than the leaf blight, early seedling infection can have devastating effects on plant survival.  The wilt phase is characterized by infected vascular tissue and bacterium movement within the plant through the water-conducting system.  Symptoms can progress from a discoloration of the xylem to a water-soaked, general wilting of plants or death.1  Once systemically infected as seedlings, plants are affected throughout the season.  Susceptible corn products can suffer severe losses during epidemics of systemic GBW. 

The leaf blight phase which usually appears mid-season, causes gray to light yellow lesions with wavy margins that roughly follow leaf veins (Figure 1). digital tool 1 Smaller, darker water-soaked flecks, often referred to as freckles, are apparent inside the larger lesion (Figure 1).  A bacteria-laden ooze may appear within the lesions in the morning and as the ooze dries, a crystalline sheen develops on the leaves.  Eventually, the lesions will fade to a tan or gray color and may blight large areas on the leaves.

Symptoms of GBW can be confused with nitrogen deficiency and abiotic disorders such as heat stress or sun scalding (Figure 2).1 
digital tool 1
Stewart’s wilt is another bacterial disease of corn with symptoms similar to both the vascular wilt and leaf blight phases of GBW.  Early stage leaf symptoms of GBW may also be confused with foliar lesions caused by the fungal disease northern corn leaf blight (NCLB).  With both diseases, lesions run parallel to leaf veins and individual lesions can be elliptical-shaped and tan with gray-green margins.

Goss’s bacterial wilt infection follows weather events in which rain and wind disseminate overwintering bacteria from infested plant residues.  Wind or hail damage to leaves and other plant parts create wounds for bacteria to enter the plant. Hot, dry weather can inhibit disease development, except in fields with overhead irrigation. In addition to infected residue, other hosts for GBW include green foxtail, shattercane, and barnyardgrass.  Infection requires leaf injury (hail, sand-blasting, wind, equipment).  Insects are not known to spread the bacterium. Seed transmission occurs at an extremely low rate and has no epidemiological impact in areas where the pathogen is present.

Planting corn products with genetic resistance to GBW is the best method to manage this disease.  Monsanto corn breeding efforts has been instrumental in providing the DEKALB® brand with a number of current and new products that have demonstrated increased levels of tolerance to GBW (Table 1).

Additional management controls include tillage methods that bury infected corn residue and rotating away from corn for two or more years with soybean, dry bean, small grains or alfalfa.  Controlling the grassy weed hosts can also help reduce the amount of inocula available to infest future corn crops. digital tool 1

Sources: 1Jackson, T. A., et. al. 2007. Goss’s Bacterial Wilt and Leaf Blight of Corn. University of Nebraska Extension G-1675.
2Wise, K. et al. 2010. Goss’s bacterial wilt and leaf blight. Purdue University Extension. BP-81-W; Compendium of corn diseases. APS Press.