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Ask Your PCA: When should growers treat nut orchards for codling moths?

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Issue Date: June 10, 2020
Jed Walton, PCA, Big Valley Ag Services, Gridley
Jed Walton

The first flight of codling moth separated into flight A and flight B the first part of May. Early indications show a healthy codling moth in the North State, so it's probable pressure will be higher than in previous years.

Early in the season, codling moth will cause nut drop and, in turn, yield loss.

The second flight occurs, depending on location in the state, mid- to late June through early July. Rather than drop, the nuts will remain on the tree, counted as off-grade and a loss at the handler.

Codling moth damages the nut and will also lead to navel orangeworm infestation. Damage from codling moth leaves an opening that allows the navel orangeworm an entry point to cause damage and create problems at hull split.

Traps should be in place by mid- to late March to determine the biofix.

Determining when to treat should be based on grade sheets and past codling moth pressure, not trap counts. Use a good insecticide and, particularly for the second flight in June, use a long residual insecticide.

There are a fair number of chemicals available for codling moth, and while pyrethroids are much cheaper, there may be more tolerance to them. There are other insecticides that can be rotated for codling moth, such as neonicotinoids that would be a better choice than pyrethroids, especially later in the season.

It's also critical before harvest to walk the orchard and look for damage. Compare those findings to the grade sheets, and get samples of the damaged nuts from the handler to identify the damage. It's important to know whether the damage is from codling moth or navel orangeworm.

This information can assist in determining the treatment program for the following season. Keep a record of blocks where damage occurred and which pests, so that an appropriate spray program is in place.

Permission for use is granted, however, credit must be made to the California Farm Bureau Federation when reprinting this item.

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