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Walnut > Year-Round IPM Program > In-Season Activities > Identifying Husk Split

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Walnut

Identifying Husk Split

Identifying husk split is critical in a year-round integrated pest management program for walnuts. If harvest is delayed after husks have split, walnut kernels can be damaged by high temperatures, molds, or navel orangeworms, which can enter nuts after husks split.

As a general rule an economic harvest is achieved when about 80% of the nuts can be shaken from the tree. Therefore, harvest nuts as soon as shaking on a few test trees removes 80% of the nuts and 95% of the nut hulls have split. If third generation navel orangeworm eggs are found in egg traps when husks are split, harvest promptly.

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Husk split
Walnuts reach full size about seven weeks after pollination.

Husk split
Mature nuts with split husks.

Husk split
Once walnut husks split in late summer or early fall, the nuts are ready to harvest.

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