New bacterium found in U.S. corn crop

by Holly Demaree
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US corn streak
Source:  Colorado State University’s College of Agricultural Sciences Broders Lab

WASHINGTON, D.C., U.S. — On Aug. 26, The U.S. Department of Agriculture (USDA) confirmed the presence of a bacterium, Xanthomonas vasicola pv. Vasculorum, in some corn crops located in Colorado, Illinois, Iowa and Kansas.

According to the University of Nebraska-Lincoln’s Institute of Agriculture and Natural Resources crop watch, the disease had only been reported on corn in South Africa, although the pathogen has caused gumming disease on sugarcane in several other countries.

The symptoms of the disease on corn plants are narrow, wavy-edged lesions. The lesions may be tan, brown or orange and occur in between the veins of the leaf on the leaves of the corn. Colorado State University’s College of Agricultural Sciences Broders Lab said symptoms have been observed as early as growth stage V7 with lesions appearing on lower leaves first. Lesions may expand over time to cover larger areas and under favorable conditions, they spread to the upper leaves. In extreme cases, lesions may extend the entire length of the leaf and coalesce to form large, necrotic areas.

Little is known about the disease, how it will affect corn production and management strategies for the disease.

Broders Lab said field observations suggest that there are differences in susceptibility among corn hybrids. Once hybrids may be screened for resistance, use of resistant or more tolerant hybrids will be the way to manage the disease. Like other bacterial diseases such as Goss’s blight, no effective chemical controls currently exist. Until more research has been conducted to determine the most effective management strategies for this disease, Nebraska-Lincoln’s Institute of Agriculture and Natural Resources crop watch advises corn producers to use standard management practices for bacterial disease. This will include the following:

-Sanitation practices to remove any infected debris from equipment between fields in order to slow the spread of the pathogen
-Use of crop rotation or tillage to reduce the amount of infected corn debris and reduce the survival of the bacteria

While both of these strategies may reduce the amount of the pathogen present, neither will eradicate the bacteria nor eliminate the risk of disease.

Currently, the USDA does not consider this plant disease to be of quarantine significance for domestic or international trade, and intends to address it like any other bacterial disease of corn.  Corn for consumption poses a negligible risk of establishment of the disease in plants, and unprocessed corn to be fed whole to animals poses a low risk of establishment of the disease in plants. Processed corn products will not transmit the disease to plants.