Warding Off Scales

Azalea Scale Infestation

Azalea bark scale (Acanthococcus azaleae) infestations can be severe. This sap-sucking scale can cause serious harm to your favorite Azalea or Rhododendron.

The adult females (1/8 inch) with their white egg sacs are most noticeable in May and June. Symptoms of their sucking include honeydew, sooty mold, and considerable leaf yellowing and die back. Infestations over several years can kill a shrub.

In addition to Rhododendrons and Azalea, this bark scale will also dine on other plants such as Andromeda, Arborvitae, Fremontia, Hackberry, Maple, Poplar and Willow, causing similar damage.

Native Cottony Maple scale (Pulvinaria innumerabilis) is another scale that attacks the phloem layer of the bark of other shrubs and trees. It has our attention particularly on Kousa Dogwoods. This scale is black (3/16 inch), and also is most noticeable in May and June when its cottony white ovisacs can litter bark and leaves. Heavy infestations may cause leaf yellowing, honeydew, stunting and die back. Cottony Maple scale can be found on plants such as Dogwood, Elm, Hawthorn, Linden, Poplar and Sycamore.

Because the nymphs for these scales live over winter in the forks and crevices of the shrub or tree, we use a dormant oil spray in early spring, and insecticidal soap, or summer oil, as needed, throughout the spring and summer to minimize the scale population. A soil injection of systemic insecticide in early spring almost always greatly reduces the scale population.

Our up-to-date certified arborists will inspect your landscape and recommend the best plant health care program for your shrubs and trees.

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