Bacterial Blight

Bacterial blight shows up as water-soaked lesions on leaves and shoots, typically during wet spring weather when plants are just leafing out. You'll notice affected foliage may curl, wilt, or drop prematurely, particularly on forsythia, Magnolia, or mock orange. The damage is most visible in years with prolonged wet springs in the Puget Sound, where high moisture and cool temperatures create ideal infection windows. Shoots and branches may have dark, sunken lesions with a greasy appearance.

This disease thrives in overhead watering, poor air circulation, and crowded plantings. Since the bacterium (Pseudomonas syringae) survives on infected plant tissue, your best management is spacing plants properly to allow air flow, avoiding overhead irrigation, and promptly removing infected branches and shoots. Maintaining healthy, vigorous plants through good nutrition helps them resist infection better. Avoid unnecessary pruning or handling of plants when wet to reduce wound entry.