Adult and intermediate-stage females form flat to moderately convex, circular scales up to 2 mm in diameter, each with a slightly raised, sub-central point which is sometimes pale. If the scale is lifted off with the point of a needle, the insect beneath is yellow and up to 1.7 mm long. Male scales are slightly paler than female scales, and are elongate-oval and half the size. The adult male is 0.7 mm long and has a single pair of wings, two pairs of simple eyes, no mouthparts and very long genitalia. First-instar nymphs are 0.3 mm long and have legs but soon settle to form circular white scales (the whitecap stage) up to 0.4 mm across. These become incorporated into the scales of subsequent stages, forming the paler subcentral point.
Damage: C. aonidum is a leaf-infesting species, but in high-density infestations it may spread to fruits, stems and trunks, and may cause premature leaf and fruit drop and stem dieback. The scales appear as circular dark spots.
An infestation appears as dark-purple to reddish-brown or black spots with paler margins, on both surfaces of shaded leaves of the host plant. Heavy infestations cause yellowing of the leaves, followed by defoliation of part or all of the host. C. aonidum prefers shade and is therefore most common in the lower part of the canopy.
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