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Disease Watch:

Bacterial Leaf Streak
Bacterial leaf streak, caused by Xanthomonas vasicola pv. vasculorum (synonym X. campestris pv. zeae), was confirmed for the first time in the United States in many counties across Nebraska in 2016, and it was also confirmed in Colorado, Illinois, Iowa and Kansas. As yet, it has not been found in the Delta region or the Southeast; however, it is always best to be on the lookout.

bacterial leaf streak on corn plants

This photo shows the elongated lesions of bacterial leaf streak on corn. When backlit,
bacterial leaf streak has bright yellow, wavy margins.

Symptoms
Symptoms on infected plants may look similar to other common diseases, sometimes causing confusion and misdiagnoses. Narrow stripes between leaf veins may initially look like the common fungal disease, gray leaf spot. Lesions can be brown, orange, and/or yellow and are often yellow when backlit. Lesions usually have slightly wavy edges in contrast to the smooth, linear lesion margins of gray leaf spot.

Epidemiology
Bacterial leaf streak has been observed on field (dent) corn, seed corn, popcorn, and sweet corn in Nebraska. The pathogen biology and disease epidemiology have not been studied enough to be well understood. Its potential impact on yield is not known in commercially available hybrids. The pathogen survives in infected corn debris from previous seasons and is thought to infect the plant through natural openings in the leaves. Irrigation and wind-driven rain, as well as warm temperatures, are thought to exacerbate the disease.

Management
Foliar fungicides used to manage gray leaf spot and other fungal diseases are not expected to effectively control this bacterial pathogen. Until more research has been conducted to determine the most effective management strategies for this disease, corn producers are advised to use standard management practices for bacterial diseases.

Cultural Practices
Sanitation practices such as cleaning debris from combines and other equipment between fields can help slow its spread to unaffected fields. In some cropping systems use of crop rotation or tillage may help degrade infected corn debris and reduce the surviving bacteria. However, neither practice will eradicate the bacterium and eliminate the risk of disease.

Information provided by University of Nebraska Extension.

10 Disease Management Tips

  1. Plant seed treated with a fungicide to reduce seed rots. A seed-treatment nematicide is also effective for management of nematodes at low to moderate populations.
  2. Rotate to non-cereal crops to prevent a buildup of certain disease organisms, including fungi, bacteria and nematodes.
  3. Plant hybrids that are resistant to problematic diseases. By selecting resistant hybrids, producers can significantly reduce the threat of diseases, such as northern corn leaf blight, southern rust and Diplodia ear rot.
  4. Plant early to help reduce stalk and ear rot problems. Charcoal rot, a disease that can cause serious damage to the stalk and significant lodging, is most severe under drought stress and, thus, typically more problematic on later-planted corn.
  5. Destroy old crop residue to help reduce problems from disease organisms.
  6. Follow good fertilization practices, including starter fertilizers and a good liming program, to promote vigorous seedling growth.
  7. Subsoil under the row to reduce compaction and promote root growth.
  8. Use approved fungicides on susceptible hybrids to reduce losses to disease and protect yield. Timing of fungicide applications is critical for disease management.
  9. Chemigation has proven effective in management of foliar diseases of corn in recent studies.
  10. Plant-parasitic nematodes are often an under-recognized problem for corn growers in Georgia. Growers should soil sample appropriately and use nematicides to minimize losses.
Source: Bob Kemerait, Extension plant pathologist, University of Georgia Corn Production Guide.