K. Korus, J. M. Lang, A. O. Adesemoye, C. C. Block, N. Pal, J. E. Leach, and T. A. Jackson-Ziems
In 2014 and 2015, Zea mays samples (field, seed, and popcorn) were submitted to the Plant and Pest Diagnostic Clinic at the University of Nebraska–Lincoln displaying long, dark, yellow to brown, water-soaked, linear lesions confined to the interveinal spaces of the leaves. Initial symptoms appeared as small water-soaked flecks that expanded between veins to form irregular lesions. In some cases, the disease progressed to cover 40 to 50% of the leaf area. The disease was confirmed by symptom expression and bacterial streaming in 41 counties in Nebraska as well as Yuma Co., Colorado, and Phillips Co., Kansas, both contiguous to Nebraska. Tape mounts taken from the abaxial and adaxial sides of the leaf revealed no fungal sporulation. However, excised leaf sections exhibited significant bacterial streaming. Yellow, mucoid bacteria were isolated on nutrient broth yeast extract agar (NBY) from symptomatic leaf tissue. . . . Based on these results, we conclude that Xanthomonas vasciola is the causal agent of bacterial leaf streak on corn in the United States. To our knowledge, this is the first report of X. vasicola occurring on corn in the United States.