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Bacterial pustule


© Iowa State University

Pathogen(s) causing disease:

Xanthomonas axonopodis pv. glycines

Symptoms:

Early symptoms are minute, pale green spots with elevated centers on either or both leaf surfaces. Later, a small, raised, light-colored pustule forms in the center, usually in lesions on the underleaf surface. The spots vary from specks to large, irregular, mottled brown areas. Leaves become ragged when dead areas are torn away by wind. Severe disease often results in some defoliation. Leaf spots sometimes form without developing pustules.

Conditions:

Occurs in hot, wet weather. The bacterium overseasons in seeds, in surface crop residue and in the rhizosphere of wheat roots. Spreads via splashing water or windblown rain and during cultivation when foliage is wet.

Management:

Plant resistant cultivars. Crop rotation can be an effective method to avoid inoculum from a previously infected crop. Incorporating crop residue by tillage will reduce the amount of inoculum available in the spring to infect plants. To prevent the spread of disease, limit cultivation to times when the foliage is dry. Scout R1 through R6. Occurs randomly, there are no high-risk areas.

Sources:

U of IL
U of NE
ISU

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