How to Manage Pests

Pests in Gardens and Landscapes

Purple blotch—Septocyta ruborum

Purple blotch causes dark green irregularly shaped lesions to form on canes of blackberries. Lesions may become brown or purple with a red margin. Small, black pycnidia develop in the center of the mature lesions. Canes eventually become girdled and, in severe cases, will die. Purple blotch does not cause leaf spots to form.


The fungus that causes purple blotch survives on infected canes. Spores are dispersed by splashing water or rain. Avoid overhead sprinklers. Prune to provide good air circulation. Control weeds to reduce humidity. Trellis canes by early September to reduce winter injury. Use an alternate-year fruiting program, where canes are trained up as they grow. After harvest and before fall rains, prune out and destroy old wood. Fungicides such as Bordeaux or a fixed copper fungicide may help provide control throughout the growing season. Spray fixed coppers after harvest. Use fixed copper or Bordeaux before fall rains begin and spray again with fixed copper in spring at budbreak.

Purple blotch lesions on canes
Purple blotch lesions on canes

Statewide IPM Program, Agriculture and Natural Resources, University of California
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