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Ask Your PCA: When should almond orchards receive a dormant spray?

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Issue Date: December 9, 2020
Jed Walton, PCA, Big Valley Ag Services, Gridley
Jed Walton

A heavy infestation of scale—European fruit lecanium or San Jose scale, and brown almond mite or European red mite—requires a dormant spray with oil. However, for most almond orchards, these pests are not widespread enough to need an annual dormant spray.

Monitor San Jose and European fruit lecanium scale by collecting spurs and examining them for live scale as well as for tiny emergence holes that indicate parasite activity. If there are a lot that are parasitized, it may not be necessary to treat them.

In-season mite damage can be seen on the leaves. Treat the mites in season, and because they will have probably laid eggs, a dormant spray is advisable as another control tool.

San Jose scale can actually kill the wood if it gets a foothold. European fruit lecanium, which is a soft scale, acts like a sucking insect; it will starve the tree by sucking the life out of it and cause a reduction in yield.

The other main reason for a dormant spray is to control scab. If scab gets a foothold, a dormant spray with copper or chlorothalonil can help to reduce the numbers, and it's been shown it provides a head start on the scab control for the next year.

Reducing the humidity in the orchard helps control scab. Though rain can't be controlled, angling sprinklers down so they don't hit high in the tree reduces the humidity in the tree.

The almond mite, European red mite and scale are not variety-specific. Scab, on the other hand, is susceptible in certain varieties.

Insecticide selection is also helpful. When possible, use chemicals that are soft on beneficials, but still provide efficient in-season control. This will help keep the beneficials active to control scale and mites.

It's important to monitor these pests and make a spray application when needed.

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




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