How to Manage Pests

Pests in Gardens and Landscapes

Walnut blight—Xanthamonas campestris
pv. juglandis

Symptoms of walnut blight may include one to several black lesions on catkins (clusters of male flowers; no fruit develop from these). Husks develop black, slightly sunken lesions at the stigma end when young; more lesions will develop on the sides of fruit as it matures. Lesions are always dry. Shoots and leaves may develop symptoms; symptoms are more common on fruit. Shoots develop black lesions and leaves show irregular lesions on blade. All leaflets of a leaf usually show signs of infection.

Identification | Life cycle

Solutions

Walnut blight is worse in early-leafing varieties. Avoid getting foliage wet with sprinklers and avoid irrigation altogether during bloom. Open up trees with pruning to get better air circulation.

Walnut blight on nuts
Walnut blight on nuts
Infection on catkins
Infection on catkins
Early fruit lesion
Early fruit lesion

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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