How to Manage Pests

Pests in Gardens and Landscapes

Leaf spot—Mycosphaerella (Septoria) rubi

Leaf spot can cause symptoms on leaves and canes of blackberries and boysenberries. The disease is named for the 0.12-inch circular lesions on the leaves. They have a brown or purple margin and, typically, a whitish center. Lesions on canes and petioles are similar to those on leaves but more elongate. Small, black pycnidia can be seen in the whitened area of the mature lesions.

Solutions

The fungus that causes leaf spot survives on infected canes and leaves. Spores are dispersed by splashing water. Avoid overhead sprinklers. Prune to provide good air circulation. Control weeds to reduce humidity. After harvest and before fall rains, prune out and destroy old wood and apply a Bordeaux or a fixed copper fungicide. Spray again in spring when new laterals are leafing out, and again when flowers begin to open. Avoid susceptible varieties. Use an alternate-year fruiting program where canes are trained up as they grow.

Spots on leaves
Spots on leaves

Lesions on canes
Lesions on canes


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

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