How to Manage Pests

Pests in Gardens and Landscapes


If nuts are continuously exposed to the sun, the husk surface may show yellowish brown spots that develop into dark brown leathery lesions by mid- or late summer. Sunburned nuts have shriveled and darkened kernels. The bark of young tree trunks and exposed limbs on older trees are also sensitive to sunburn. Sunburned bark is cracked and appears bleached.



To minimize sunburn damage to nuts, maintain a healthy foliage with adequate irrigation, fertilizer, and other cultural practices. Control aphids on early varieties, such as 'Payne', as honeydew produced by aphids can contribute to sunburn. Paint tree trunks with whitewash or a white, water-based paint to protect them against sunburn.

Sunburned walnut husks
Sunburned walnut husks

Darkened and shriveled kernels
Darkened and shriveled kernels

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