CALIFORNIA RED SCALE (CRS): Aonidiella aurantii (Maskell) Order - Homoptera: Family - Diaspididae

DISTRIBUTION: Citrus growing areas in US and elsewhere. CRS is found in isolated pockets of Maricopa County and Pima County. None is known in Pinal County. Although CRS can sporadically be found in Yuma County (AZ) and areas of Imperial County (CA), because of suppression efforts, these areas are considered scale free.

DESCRIPTION:Eggs hatch before being laid, the young are born as live “crawlers”. Crawlers are mobile (visible with a strong hand lens) and are bright yellow as they come out from under the stationary waxy coating (shield) of the ♀. ♀ and ♂ crawlers select a feeding site and begin to form a waxy coating called a whitecap (visible as small white dot). They loose their legs and antenna and the shield becomes darker and larger through successive molts. They are now called instars or nymphs. The ♂ grows darker than the ♀. His covering is smaller (0.8-1.2 mm in diameter) and more elongate. The vertical arrow in figure one points to an immature ♂. Two eye-dots are visible after the 2 nd ♂ instar. This is the pupal stage (Fig 2) which is applicable to the ♂ only.

Adult ♀s (Fig 1 indicated by horizontal arrow) are stationary on the host; circular, flat, and appear orange-red. They are translucent. Their margins are parchment-like and they are approximately 1.5-2 mm in diameter. Their exuviae (nipples) are usually centrally located. Authoritative identification is made by microscopically examining the bodies found under the shield. Adult ♂s (Fig. 3) are very small (about the size of a dust particle), golden in color, and are identified by a brownish red band across the thorax.

HOSTS: Citrus and hundreds of different plant species including euonymus, wax leaf privet, holly, sago palm, cocculus, and rose.

DAMAGE: CRS attacks all parts of the tree above ground. Heavily infested fruit (Fig 4-6) may be downgraded in the packinghouse and may become unmarketable. Trees with large populations will become severely stressed resulting in poor vigor and loss of production.

INSPECTION TIPS: Populations are usually highest in late fall, but any time of the year is satisfactory for detection. Careful attention should be given to northeast portions of the tree and the interior area shaded by the canopy. Some yellowing around scale may be visible on leafs. In nurseries, pay careful attention to favored host plants in shade areas. ♂s may be trapped using pheromone attractants.

LIFE CYCLE: 2-4 generations overlap. Overwintering takes place in all instars. Young ♀s and crawlers are active throughout the year. In Maricopa County, ♂ flights peak once or twice in April/May. ♂ flier numbers spike dramatically in August/September. Crawlers are most abundant in three periods: late January/February, May/June, and September/October. A ♀ produces 60-150 nymphs over a 10-day period. After 2-4 hours the nymphs leave the ♀ scale and disperse. The final molt usually occurs in 6 weeks.

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