Origin:
Possibly native to temperate climates in the U.S., and now found from California to Florida.
Biology:
The Wax scales in the genus Ceroplastes attack over 50 different ornamental and forest plants, including holly, pyracantha, juniper, hemlock, boxwood, gardenia, and others, including citrus. The visible scale is the female, which overwinters in this stage. In the spring hundreds of eggs are deposited within the scale, and these hatch to the crawler stage. This mobile stage will move to other parts of the plant. They eventually settle in after they molt and become sessile as well, covering themselves with layers of wax they produce. Males are virtually unknown for some wax scale species. There may be 2 or more generations per year.
Identification:
The wax scales have a heavy, irregular shape and are coated with a thick layer of wax. The barnacle scale is one of the largest of the group at over ΒΌ inch across. It can be separated from others in the group by the larger size and pearly gray color. There are several dark patches around the base of the scale and a single dark spot in the center on top.
Characteristicts Important to Control:
For light infestations hand removal of the scales may be sufficient, particularly if done in the winter before the eggs hatch. Spray applications of a labeled insecticide should be timed for when the eggs are hatching, and the visible crawlers are moving about on the plant. Once they become sessile and covered with wax topical sprays may not reach the actual insect. A soil or trunk applied systemic, such as imidacloprid, may be effective by allowing the active ingredient to enter the foliage where the scales will ingest it.
