Goss’s Wilt of Corn, Diagnosis and Management

Two phases of Goss’s wilt may occur within the corn plant; a systemic wilt occurs at the seedling stage and leaf blight can occur in the late stages of corn plant growth. The leaf blight phase (Figure 1) is generally more prevalent and is characterized with the appearance of large, wavy lesions that are brown, yellow, or gray in color. These lesions may be elliptical or V-shaped that typically extend down the leaf veins and often coalesce forming larger lesions (Figure 2). Dark green, tan, or black spots, termed “freckles” are found within the margin of the expanding lesion (Figure 3). When these “freckles” are observed against the light, transparent spots can be seen (Figure 4). The bacteria can also create an exudate or “ooze” on the surface of the leaf, which when dry gives a shiny appearance.

Goss’s leaf blight can often be misidentified as other diseases such as Stewart’s wilt and northern corn leaf blight as they exhibit some of the same symptoms. Goss’s wilt can also be easily confused with drought stress, leaf scorch, nutrient deficiency, or chemical injury. For confirmation of Goss’s wilt, it is a good practice to submit a sample to a diagnostic lab for testing.

The less common phase is systemic wilt. Symptoms of early infection resemble drought stress and can wilt or die prematurely (Figure 5). Vascular stalk tissue displays a brownish-orange discoloration when infected by the bacteria (Figure 6).

The pathogen for Goss’s wilt overwinters and can survive in infested corn residue for 10 to 15 months.^2,3,4 The pathogen can also survive in other plants such as ryegrass, several foxtail species, Johnsongrass, large crabgrass, big and little bluestem, shattercane, and grain sorghum.^2,3,4 Infested corn residue is the primary inoculum source followed by infested grasses.

The bacteria enter the corn plant through plant wounds resulting from hail, sandblasting, wind, and heavy rain, as well as natural leaf openings. Warm temperatures (80^◦ F) are optimal for disease development and leaf blight symptoms often become more apparent after silking.

Unfortunately, there is no in-season rescue measure to manage Goss’s wilt as fungicides do not control bacterial diseases. Avoidance, prevention, or minimization of the disease is crucial.

The best management strategy for Goss’s wilt is product selection. Corn products with good tolerance can reduce the disease’s impact on yield potential. Other strategies involve the potential reduction of inoculum. Crop rotation and tillage can be effective in reducing the amount of corn residue. Rotating out of corn into other crops such as soybean, dry bean, small grains, or alfalfa can help reduce the primary inoculum source. Deep tillage can also be very effective in incorporating and burying infected residue.