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.
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