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Ask Your PCA: How should farmers control thrips in citrus?

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Issue Date: March 10, 2021
Chris Boisseranc PCA, Southwest Ag Consulting Inc., Redlands
Chris Boisseranc PCA, Southwest Ag Consulting Inc., Redlands

Thrips are a cosmetic pest, but have a significant impact on fruit quality. They will scar the immature fruit immediately after the flowering stage is complete and the fruit has set on the tree.

Thrips live in the flower and scar the top of the fruit. As the fruit sizes and matures, the scar enlarges. Losses can be as high as 20% if thrips are left unchecked throughout the season.

There is about a two-month period of susceptibility where thrips are able to scar the fruit. Once the fruit hardens off, it's no longer susceptible to thrips.

Thrips are mainly an outside canopy pest where there is new growth, and they prefer the dry exterior of the tree and the light.

Thrips pressure is weather-dependent. Warm and dry weather during the susceptible period will result in thrips pressure. With a humid and wet spring during the susceptible time, thrips may not be a problem.

In Southern California, the Asian citrus psyllid treatments during the season can make the thrips populations more active and result in having to treat more frequently. In the past, applications weren't made if the weather wasn't conducive to problems with thrips, but with the ACP protocol it's become almost automatic that there is thrips pressure and sprays are applied every year.

Several materials are available for thrips, both organic and conventional. There are about five chemicals used for conventional and two or three for organic operations. The chemicals should be rotated to avoid problems with resistance building.

There are native beneficials that work continually in the trees. Some years, the beneficials are significant and they will hold down the thrips population and cause only superficial damage. But because there is a tight window with the thrips and the populations are so explosive, a chemical treatment is generally required.

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

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