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Foliage development showing mature leaves with immature nuts.Why Is the Nut Development Period Important in an IPM Program?

The nut development period is an important period for the monitoring and management of many walnut pests such as walnut blight, codling moth, walnut scale, aphids, spider mites, walnut husk fly, and weeds in an IPM program.

It is important to maintain the walnut blight and codling moth management programs throughout the fruit development period. If decisions are made to treat for codling moth, use treatment options that do not pose water quality problems such as mating disruptants, insect growth regulators, and other reduced risk pesticides.

Because the husks of some walnut varieties crack before harvest, they are often more vulnerable to navel orangeworm damage. Planning a prompt harvest after husk split is an important way to limit navel orangeworm infestations in walnuts. Where navel orangeworm is a major problem, plan on an early and rapid harvest. Growth regulators can be applied to advance husk split. Also note, that after husk split, husk flies no longer pose a problem.

Programs that rely on natural enemies, cultural practices, and lower-risk pesticides pose fewer water quality and environmental risks than programs that rely on organophosphate or pyrethroid insecticides.

For more information on monitoring and management see the individual pest sections of the Walnut Pest Management Guidelines.

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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