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Fletcher Scale

June 18, 2003

Fletcher scale (Parthenolecanium fletcheri) is a common pest in nurseries and on sheared hedges in landscapes. This scale feeds on arborvitae (Thuja spp.) and yews (Taxus spp.) and has been known to feed on Pachysandra. On yews, they are generally located deep within the plant canopy. The female scales are about 1/4 inch long, round, and deep brown when mature. In Illinois, eggs hatch between May and early July into oval, flat, yellowish crawlers. Females lay around 500 to 600 eggs and are capable of producing up to 1,000. Crawlers are active from mid-June to mid-July. They tend to congregate and feed on twigs and stems deep within the plant canopy. Fletcher scale–feeding weakens plants, causing foliage to drop. They produce copious amounts of honeydew, an excellent growing medium for black sooty mold fungi. There is one generation a year in Illinois.

Insecticides recommended for Fletcher scale include acephate (Orthene), insecticidal soap, and summer oil. Apply in mid- to late June when crawlers are active or when hills of snow hydrangea are in full bloom- because the early crawlers are most susceptible to insecticides. Be sure the sprays penetrate the entire plant canopy.

Natural enemies may cause rapid decline in Fletcher scale populations because many predators are effective in controlling crawlers. As a result, use insecticides that are less harmful to natural enemies. Avoid broad spectrum insecticides (that is, acephate) that may kill natural enemies.

Author: Raymond A. Cloyd


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