Wednesday, May 21, 2008

Pest Alert: Euonymous scale


Adult females are about 1-2 mm –grey-brown in color, and oystershell in shape. Adult males are smaller, elongate, and white. Crawlers are yellowish-orange and difficult to see clearly without a magnifying lens. Infestations are first visible as yellowish-white spots on the leaves, and heavy infestations can cause a whitewashed appearance on the plant.

All varieties of Euonymous (including Burning Bush, Wintercreeper, and the Variegated Eounymous bushes) are attacked by this insect. Other known hosts are hollies, camellias, privets, honeysuckle, and others. Damage is caused to the plant by piercing-sucking mouth parts of crawlers (nymphs) and adults, and often infest heavily enough to cause leaf drop. Continuous leaf drop leads to the death of the plant.

Fertilized adults will overwinter on the stems, eggs beneath the female shell hatch over several weeks (usually late May-early June) and nymphs disperse by crawling or being blown in the wind. They mature in about 6 weeks, adults produce eggs again, and the second generation crawlers appear in late July-mid August.

Control is best when applied during the crawler stages. Prune and destroy heavily infested plant parts, or remove the entire plant (including roots).

There is also a Winged Euonymous scale which are darker in color, and more closely resemble the oystershell scale. This scale can be found more commonly on E. alatus, E. fortunei, Pachysandra, Salix and Cornus; and had been found attacking the same plants as the Euonymous scale, making identification and control more challenging.