Bacterial leaf streak disease of corn, caused by Xanthomonas vasicola pv. vasculorum, has been confirmed in some Nebraska cornfields. The disease had not been previously identified in the United States, but had been reported on corn in South Africa.
The bacterium also causes gumming disease in sugar cane in numerous other countries. The species has undergone name changes and is recognized by several other synonyms.
Surveys are currently under way across the Corn Belt to identify the disease distribution and raise awareness. Initial observations and survey results suggest that it may be widely distributed and established throughout the Corn Belt. Eradication is not thought to be possible. Additional research is planned and underway to better understand its biology and best management practices.
Unusual symptoms were first reported on corn samples received by the University of Nebraska-Lincoln Plant and Pest Diagnostic Clinic in 2014.
Identification was delayed because of the lack of historic research on the pathogen and limited data available on this bacterium and its close relatives.
Advanced and multiple testing procedures were conducted on the bacteria at multiple institutions to confirm its identity. Third-party confirmation of the bacteria was conducted by the USDA Animal and Plant Health Inspection Service. Collaboration between agencies was critically important to obtaining a correct diagnosis.
Although its appearance may be similar to other common fungal and bacterial diseases — e.g., gray leaf spot – foliar fungicides are not expected to control the bacteria causing this disease. Typical management strategies for bacterial diseases are recommended.
This pathogen survives in infected crop residue. Sanitizing equipment to remove infected crop residue prior to moving between fields may help slow its spread.
Although research is incomplete, crop rotation may also help reduce the impact of the disease, but will not eliminate the pathogen.
Symptoms of this disease appear similar to those of several other diseases and are typically narrow tan to brown streaks between leaf veins. The disease causes lesions that usually have wavy margins in contrast to smooth, linear rectangular lesions observed with the common fungal disease, gray leaf spot.
Last week the USDA’s National Agricultural Statistics Service reported the following crop conditions in Nebraska.
-- Corn condition rated 1 percent very poor, 5 poor, 19 fair, 59 good and 16 excellent. Corn dough was 95 percent, ahead of 89 last year, and near the five-year average of 92. Dented was 61 percent, ahead of 53 last year and 56 average. Mature was 5 percent, near 1 last year and 7 average.
-- Sorghum condition rated 0 percent very poor, 0 poor, 17 fair, 64 good and 19 excellent. Sorghum coloring was 74 percent, well ahead of 39 last year and 36 average. Mature was 2 percent.
--- Soybeans condition rated 1 percent very poor, 3 poor, 19 fair, 61 good and 16 excellent. Soybeans setting pods was 96 percent, near 95 last year, and equal to average. Dropping leaves was 8 percent, near 9 last year and 4 average.
-- Winter wheat planted was 1 percent, equal to average.
-- Alfalfa condition rated 4 percent very poor, 4 poor, 18 fair, 62 good and 12 excellent. Alfalfa third cutting was 93 percent, near 92 last year, and ahead of 86 average. Fourth cutting was 37 percent, ahead of 27 last year, and well ahead of 17 average.
-- Dry edible beans condition rated 1 percent very poor, 4 poor, 33 fair, 52 good and 10 excellent. Dry edible beans blooming was 93 percent. Setting pods was 88 percent, behind 98 last year and 97 average. Dropping leaves was 19 percent, behind 26 last year, but near 16 average.
-- Proso millet harvested was 6 percent, near 2 average.
-- Livestock, Pasture and Range Report: Pasture and range conditions rated 3 percent very poor, 9 poor, 23 fair, 55 good and 10 excellent.
-- Stock water supplies rated 1 percent very short, 12 short, 86 adequate and 1 surplus.