Bacterial leaf blight of wheat
Bacterial leaf blight, caused by Pseudomonas syringae pv. syringae, is not of major economic importance in wheat. After prolonged periods of high humidity, water-soaked spots develop on flag leaves and below on infected plants. Affected areas can range from small flecks to large blotches on leaves. Once humidity decreases, spots will turn gray/green, become tan and bleached over time, and coalesce, sometimes killing the entire leaf. Bacterial leaf blight lesions can be observed from stem elongation stages through ripening and typically appear earlier in the growing season than bacterial streak.
Anything that wounds the plant, such as hail, wind, or mechanical damage, can create an entry point for the bacterium. Temperatures between 60 and 77°F favor disease development, along with cloudy, humid, and rainy weather. Wheat is most susceptible to infection near FGS 10.0 (boot stage).
Planting resistant varieties is the only known way to manage bacterial leaf blight.
Gallery Images: M. Burrows