Euonymous, Anyone?

In this case, you might want the shrub or vine, euonymous, but not the common euonymous scale insects that often infest them. In fact, in some landscapes, the scale infestations are so common that budding horticulturists and entomologists often think that the symptoms and signs are a natural occurrence, as in “they’re supposed to be there”. Many homeowners simply think that the white flecks offer a two toned feature to the leaves and stems.

But, wait, they’re not supposed to be there? No. These insects live and thrive on the leaves and stems of wintercreeper, Japanese euonymous, spreading euonymous and other species such as pachysandra by sucking sap and plant juices to feed themselves. The damage they cause first appears as yellowed leaves, then progresses to thin foliage and dead branches.

Euonymous scales belong to a group of insects called the “armored scales”, with distinct white (male) and brown (female) waxy coverings. The males are slightly smaller than the females, however, both are in the 1/16th inch range.

The key to controlling them is knowing their life cycle, which begins in April, where they live as nymphs under the protection of the tortoise shell like covering of the female. They hatch and begin moving on the stems in late spring and early summer. At this point in time they are vulnerable to control efforts such as applications of permethrin, horticultural oil or insecticidal soap. Several applications are usually necessary to achieve complete control. Because they usually attach themselves to the undersides of leaves as well as other plant parts, thorough coverage is required.

As they mature, they produce a waxy covering of their own and become resistant to control efforts. A second generation is produced in late July and early August, producing nymphs that mature and spend the winter undercover.

In addition to the foliar sprays, a systemic application of imidacloprid can also be made. Because this product usually requires 4-5 weeks to be absorbed and moved to the active feeding parts of the plant, a mid-fall treatment timeframe is recommended. If a particular specimen is especially valuable, and heavily infested, then dead stem removal, systemic insecticide drenches and foliar applications are all recommended. Removal of the entire plant is also a viable option, directing efforts towards other plants that are lightly infested.

As with all pesticide products, read and follow all label instructions.

John Fech
Horticulture Extension Educator at Nebraska Extension
John Fech is a horticulturist with the University of Nebraska-Lincoln and certified arborist with the International Society of Arboriculture. The author of 2 books and over 200 popular and trade journal articles, he focuses his time on teaching effective landscape maintenance techniques, water conservation, diagnosing turf and ornamental problems and encouraging effective bilingual communication in the green industry. He works extensively with the media to extend the message of landscape sustainability, making over 100 television and radio appearances each year.
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