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Wax Scale

ID

444-622

Authors as Published

By Eric R. Day, Director, Insect Identification Laboratory, Virginia Tech

Homoptera: Coccidae, Ceroplastes ceriferus

Plants Attacked

Wax scale has well over 50 hosts, especially Japanese and Chinese hollies, pyracantha, spirea, ivy, hemlock, euonymus, and boxwood.

Description of Damage

Infestations seldom kill plants directly, but seriously weaken them, reduce growth, and cause decline. Deposits of honeydew give rise to rampant growth of the black sooty mold fungus, particularly on burford and Chinese holly.

Identification

From August until June adult female scales are large, up to 1/4 inch, bright white, and circular. On certain hosts, they may reach only 1/8 to 3/16 inch. Dead scales remain on the twigs, but turn dull and gray, and may be covered with sooty mold. When wax is initially produced, the scale looks like a cameo. The next instar is called the dunce cap stage due to the conical shape of the wax produced. The wax scale, Ceroplastes ceriferus, is in the order Homoptera and family Coccidae. Ceroplastes ceriferus also goes by the common name Indian wax scale.

 

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Life History

Females overwinter as completely mature adults. Egg laying begins in late April. It is two to four weeks or more before the eggs hatch. Hatching can take place any time from June 1 to 23, depending on geographic location. Development through the cameo and dunce cap instars takes place during late July and August. Females are mature by late August or September. Wax scales settle and remain on the twigs and stems. Only where very dense populations exist will crawlers settle on leaves and fruit. There frequently are variants in the populations, such as a few eggs hatching as late as July. Adult females lay 1,500 to 2,000 eggs on average and may lay as many as 3,000 or more.

Control

Carbaryl has given complete control, even if the timing of sprays is not precise. Applications are best if made when eggs start to hatch. In test plots, one application was as effective as two or three at two-week intervals. Treatments anytime in June should give complete control if thoroughly applied. Other insecticides give good results if applied two or three times at weekly intervals, but a few scales are likely to survive. In light infestations, wax scale adults may be picked off the plants manually. During the fall and early winter, they can be dropped on the ground. During February, March, and April, they should be destroyed.

Remarks

Wax scales on cut branches or picked from stems in late spring will proceed to lay eggs. Eggs may hatch and crawlers are likely to infest any nearby plants. The wax scale has not been found generally west of Danville, Lynchburg, Charlottesville, or Loudoun County.

Rights


Virginia Cooperative Extension materials are available for public use, re-print, or citation without further permission, provided the use includes credit to the author and to Virginia Cooperative Extension, Virginia Tech, and Virginia State University.

Publisher

Issued in furtherance of Cooperative Extension work, Virginia Polytechnic Institute and State University, Virginia State University, and the U.S. Department of Agriculture cooperating. Alan L. Grant, Dean, College of Agriculture and Life Sciences; Edwin J. Jones, Director, Virginia Cooperative Extension, Virginia Tech, Blacksburg; Jewel E. Hairston, Administrator, 1890 Extension Program, Virginia State, Petersburg.

Date

May 1, 2009


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