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Scurfy Scale

May 4, 2005

Now is time to be on the look out for the crawler stages of scurfy scale, Chionaspis furfura, that have emerged from eggs. This scale species is primarily a pest in nurseries but can also be found in ornamental plantings. Scurfy scale tends to attack plants in the rose family (Rosaceae), including cherry, crabapple, firethorn, hawthorn, mountain ash, peach, and quince. Other susceptible hosts include dogwood, elm, hickory, horsechestnut, maple, and willow. Scurfy scale is not one of the more common scales found in Illinois; however, there have been increased reports of infestations within the last couple of years.

Female scurfy scales are flat, thin, grayish white, 1/8-inch long, and rounded on one side, which makes them appear pear- or oystershell-shaped. Females can lay up to 80 eggs, which are reddish purple in color. The eggs are retained under the female covering after she dies. Scurfy scale overwinters in the egg stage. Eggs typically hatch in mid to late spring, depending on temperatures, into purple crawlers that move around on plants and eventually locate a suitable place to settle and feed. Scurfy scale can be abundant on bark, resembling flakes on the surface of skin, giving the plant a “scurfy” appearance (hence the common name). This scale tends to be located on the shady side of trees or in areas under the dense canopy of leaves. Scurfy scale is a hard scale, which means that no honeydew is produced during feeding. In Illinois, there are one to two generations per year.

Scurfy scale is best managed when the crawlers are active. Insecticides recommended for control include acephate (Orthene), bifenthrin (Talstar), cyfluthrin (Tempo), insecticidal soap, or a summer (horticultural) oil. This scale is susceptible to dormant oil sprays during the winter.

Scurfy scale (like many scales) is susceptible to parasitoids and predators (= natural enemies); and in sufficient numbers, these natural enemies may provide some level of control. The use of acephate, bifenthrin, cyfluthrin, or other persistent, broad-spectrum insecticides is harmful to natural enemies, which may impact their ability to provide control. Insecticides such as insecticidal soap and summer oil are less harmful to natural enemies.

Author: Raymond A. Cloyd


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