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Bacterial Leaf Streak in Corn

January 15, 2025

Bacterial leaf streak (BLS) was first documented in the United States in 2016, but symptoms of the disease were observed earlier in Nebraska in 2014.1 The disease has been found in Colorado, Illinois, Iowa, Kansas, Minnesota, Nebraska, Oklahoma, South Dakota, and Texas.1,2 Bacterial leaf streak is caused by the bacterium Xanthomonas vasicola and has been found on corn, sugarcane, and various grass weed species. Currently, no product is available to protect other plants once infection is present in the field. Yield or quality losses have only been found when infection is severe prior to grain fill.

Epidemiology

The BLS pathogen survives in previously infected plant residue. Secondary infections occur when bacterial exudates from infected plants are transported to healthy plants by wind, rain splash, or overhead irrigation water.3 Additionally, the use of overhead irrigation when temperatures are above 90 °F is associated with an increase in disease incidence.

The pathogen penetrates corn leaves through the stomata, resulting in a typical banding appearance or pattern as lesions develop on the leaves. The pathogen appears to be restricted to areas between the main veins and does not invade vascular tissue. Because it is not systemic, it does not result in wilting like Goss’s wilt or Stewart’s wilt. While foliar lesions covering almost 40% of the leaf surface have been observed, no subsequent yield reduction was documented. Several weeds and other grass crops have been identified as host plants, including rice, oats, timothy, shattercane, Johnsongrass, green foxtail, yellow nutsedge, and downy brome.3

Symptoms

Symptoms can occur at any stage of corn growth but are typically first observed on lower leaves with spread to the middle and upper portion of the crop canopy after flowering. Initial symptoms appear as translucent, water-soaked streaks between veins (Figure 1) and progress to longer yellowish to necrotic streaks that can coalesce to form larger areas of symptomatic tissue (Figure 2). Bacterial exudates on the leaf surface may appear as small, dried, yellow droplets. Bacterial leaf streak lesions coalesce as leaf tissue dies, creating larger areas of necrosis.

Figure 1. Lesions of initial infection by bacterial leaf streak. Image courtesy of Emmanuel Byamukama, South Dakota State University.


Lesions of intermediate infection by bacterial leaf streak
Figure 2. Lesions of intermediate infection by bacterial leaf streak. Image courtesy of Emmanuel Byamukama, South Dakota State University.

Diseases with Similar Symptoms

Gray Leaf Spot

Gray leaf spot (GLS) lesions look similar to BLS lesions. However, GLS lesions tend to be more rectangular with sharply defined edges while BLS lesion margins are wavy (Figure 3). When backlit, GLS lesions are opaque with yellow margins, but BLS lesions are translucent (Figure 4).

Bacterial leaf streak on left with wavy lined edged lesions, compared to gray leaf spot on right with straight-edged lesions. Image courtesy of Emmanuel Byamukama, South Dakota State University.
Figure 3. Bacterial leaf streak on left with wavy lined edged lesions, compared to gray leaf spot on right with straight-edged lesions. Image courtesy of Emmanuel Byamukama, South Dakota State University.


Bacterial leaf streak lesion
Figure 4. Bacterial leaf streak lesions that are translucent when backlit. Image courtesy of Emmanuel Byamukama, South Dakota State University.

Common Rust

Common rust may be mistaken for BLS. However, common rust produces pustules, lesions that are raised and blister-like (Figure 5). When backlit, the pustules appear as dark circles.


Common corn rust.
Figure 5. Common rust lesion with pustules appearing as spots within the lesion.

Diplodia Leaf Streak

Early Diplodia leaf streak (DLS) symptoms include dark, water-soaked, linear lesions that become tan with long, parallel sides and a bright yellow halo (Figure 6). As DLS lesions mature, they become more elliptical and look less like BLS. Additionally, small black spots (pycnidia) may appear in the center of mature lesions of DLS.

Diplodia Leaf Streak
Figure 6. Early Diplodia leaf streak symptoms. Photo courtesy of Kiersten Wise, University of Kentucky.

Southern Corn Leaf Blight

Mature southern corn leaf blight lesions can have brown to tan lesions with wavy sides and yellow halos in the lower canopy that resemble bacterial leaf streak (Figure 7). Southern corn leaf blight lesions are generally 1/8 to 1 inch long, but lesion length depends on corn product genetics.


Southern corn leaf blight lesions
Figure 7. Southern corn leaf blight lesions.

Management

Because BLS is caused by bacteria, fungicides are not effective in managing this disease.2,3 The following management strategies may be more effective:

  • Crop rotation to a non-host crop, such as soybean, wheat, or alfalfa.
  • Control weeds and volunteer corn as they can harbor the bacteria from year to year, particularly the many grass weed hosts.
  • Fall tillage can help speed up the breakdown of crop residue, resulting in lower inoculum levels. However, this control strategy must be balanced with the risk of soil erosion.
  • Clean equipment to reduce the spread of inoculum between fields.


Sources

1Robertson, A. et al., 2016. Bacterial leaf streak of corn. Crop Protection Network. CPN-2008. doi.org/10.31274/cpn-20190620-000

2Jackson-Ziems, T. Bacterial leaf streak. University of Nebraska Extension. https://cropwatch.unl.edu/bacterial-leaf-streak.

3Sivits, S. and Jackson-Ziems, T. 2019. Bacterial leaf streak of corn in Nebraska. University of Nebraska Extension. https://cropwatch.unl.edu/2019/bacterial-leaf-streak-corn-nebraska.

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