Azalea Bark Scale
Eriococcus azaleas Comstock, Eriococcidae, HEMIPTERA


Adult - The adult female azalea bark scale is dark red with short legs and antennae and long, sucking mouth- parts. The insect is hidden from view by the egg sac, a covering of felted or matted waxy threads (Color Plate 1B). The sac is about 3 mm long and 1.5 mm thick

Egg - The egg is laid within the egg sac, occupying the void left by the female's shrinking body

Nymph- The tiny nymph hatches from the egg and ven- tures out of the egg sac. It soon penetrates the bark with its long, sucking mouthparts and begins to feed. The nymph is inconspicuous and practically free of any waxy covering.


Distribution - The azalea bark scale occurs in the eastern United States; it has also been reported in Belgium, Germany, and Russia.

Host Plants - The azalea bark scale has been found on four azalea species, rhododendron, "flowering cherry," and huckleberry

Damage - Since its discovery in 1881, the azalea bark scale has become recognized as a prominent pest of azaleas. Infested plants usually appear chlorotic and unthrifty. The bushes are often covered with sooty mold, a black fungus that grows in the honeydew excreted by the azalea bark scales as they feed. Eventually twigs may die back.

Life History - As the female azalea bark scale matures, it secretes white, waxy threads, which become felted or matted into a thick covering over its entire body. This covering is called the egg sac, where eggs are laid after mating. As the female lays eggs, its body shrivels gradually. A until the egg sac is almost completely filled with eggs. Eggs are laid in late April. They hatch in about 3 weeks. This new generation matures during the summer and produces eggs in September. Mature females tend to feed in crotches and on twigs. Adult males, two-winged and tiny, tend to feed on the leaves. Azalea bard scales overwinter as nymphs feeding on the bark.


Adult females and eggs are protected by the egg sac from virtually any pesticide. The key to control is treatment in late spring and late fall when the nymphs are present. For specific controls, see the current state extension service recommendations.

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