Extension Staff Join with other Agencies to Survey Illinois for New Corn Disease

The USDA just announced the presence of Bacterial leaf streak in corn, as determined by recent surveys of the Corn Belt states. In Illinois, a cooperative survey was organized with APHIS-PPQ (Animal Plant Health Inspection Service), IDA (Illinois Department of Agriculture), CAPS (Illinois Natural History Survey's Cooperative Agricultural Pest Survey) and University of Illinois Extension to provide a rapid response to determine distribution.

In a short time window, the surveyors examined randomly selected fields in transects across 68 of Illinois's 102 counties. They looked for Bacterial leaf streak symptoms in approximately 340 fields across the state. The visual symptoms of this disease closely resemble Gray leaf spot, a very common corn disease in Illinois. Leaves with suspicious symptoms were collected and have been sent to a USDA laboratory for evaluation. The Extension surveyors consisted of volunteers from the Commercial Agriculture, Small Farms and Local Foods and the Energy and Environment teams.

One positive sample of Bacterial leaf streak was found in DeKalb County, IL and identification was verified by the USDA yesterday. This is the only county in Illinois that has been verified to have the disease.
So far, Bacterial leaf streak has been identified in 9 states:

• Colorado
• Illinois
• Iowa
• Kansas
• Minnesota
• Nebraska
• Oklahoma
• South Dakota
• Texas

Bacterial leaf streak is caused by the pathogen Xanthomonas vasicola pv. vasculorum.. The disease causes the formation of linear lesions between the veins on a corn leaf. The lesions look similar the gray leaf spot (GLS) symptoms. GLS lesions tend to be shorter, more rectangular and stay within their veinal borders. Bacterial leaf streak lesions are more irregular, often thinner and longer, will "bleed" over the veinal border and may have a halo when held up to the light.

Photo 1 courtesy of Nicole Furlan, USDA-APHIS-PPQ, Des Plaines

In Great Plains states that have found the disease, the disease appears first on the lower leaves and progresses up the plant. Typically this is under pivot irrigation. However later infections may occur and show up primarily in the upper canopy. There is currently very little known about this disease. Further research is needed to develop a complete understanding of this disease, its impact and strategies for long term management. However, APHIS notes it is not believed to present a health risk to people or animals.

Photo 2 courtesy of Greg Rentschler State Plant Health Director Illinois USDA APHIS PPQ

Since this is a bacterial disease, fungicides cannot be expected to control or suppress this disease. Crop rotation and tillage are the best short-term management strategies if the disease is present in a field. Differences in varietal susceptibility may point the way to sources of resistance.

If you suspect Bacterial leaf streak submit a sample to the University of Illinois Plant Clinic.

We would like to get a comprehensive idea of distribution in the state. For more information on Bacterial leaf streak, please check out these websites, hosted by our Great Plains colleagues:

Tamra Jackson-Ziems, Nebraska Extension Plant Pathologist

Dr. Kirk Broders – Colorado State University