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KAC Citrus Entomology
University of California
KAC Citrus Entomology

California Red Scale

California red scales infesting citrus fruit
California red scales infesting citrus fruit


Basic Information

Life Cycle: California red scale, Aonidiella aurantii, starts its life cycle as a crawler that emerges from a female scale, the crawler finds a leaf, twig or fruit to settle down on and inserts its threadlike mouthpart.  If female, the scale molts twice and matures through 2 nymphal instars into the virgin female stage, that is receptive to mating with a male.  If male, the scale molts from 1st to 2nd instar, then prepupa, pupa, and finally becomes a winged adult.  The entire lifecycle requires about 6 weeks to complete. For more information on the lifecycle see ANR publication 21529 CRS lifecycle Pub 21529.

Host List: California red scale is found primarily on citrus.  It can attack all varieties of citrus but reproduces better on lemons and grapefruit. 

Damage:  If fruit is infested with more than 10 scales and they are not washed off in the packinghouse, then the fruit may be downgraded from 'Fancy' to 'Choice' or 'Juice' grade.  California red scale injects a toxin when it feeds. Trees that become heavily infested experience dieback of branches leading to lower fruit production and poor health of the tree. 

Distribution: Found in most citrus growing regions of the world and throughout California citrus. 

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