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High-Pressure Washer Removes Red Scale for Citrus Fruits

The Issue

California red scale is one of the key pests of citrus in California. This pest can damage and kill citrus trees when it attains very large populations, which is a rare occurrence. The more common economic damage results from these scale insects settling on the fruit, causing cosmetic flaws and a downgrading of the fruit. Significant economic losses from this cosmetic damage occur at much lower population densities than the high densities required to damage the trees. Consequently, there is a very low threshold for California red scale in citrus orchards. To keep populations below the threshold, growers have traditionally relied on high-volume sprays (up to 1,000 gallons per acre) of insecticides.

What Has ANR Done?

A team of Agricultural Experiment Station researchers from the University of California, Riverside (G. P. Walker, Entomology; J. G. Morse, Entomology; and M. L. Arpaia, Botany and Plant Sciences) collaborated with the FMC Corp. in the mid-1990s to develop a device that removes California red scale from fruit after harvest, thus greatly reducing the need for pesticide use in the field. The device, referred to as a high-pressure scale washer, relies simply on a high-pressure water spray without any pesticides. Scale are removed by the physical impact of the sprays.

The Payoff

High-Pressure Scale Washers Used in Majority of California Packinghouses

This method of pest control has been very successful, and today high-pressure scale washers are used in the great majority of citrus packinghouses in California. This method has aided the use of biological control strategies by reducing pesticide use that might otherwise interfere with the natural enemies that control citrus pests.


Supporting Unit: UCR Entomology Department

Dr. Gregory Walker
Boyden Lab 211
University of California
Riverside, CA 92521
(909) 787-5808 (Voice)
(909) 787-3086 (Fax)