Euonymus Scale – Chalet

Euonymus scale is an insect that affects Euonymus coloratus (groundcover), Euonymus Sarcoxie and Euonymus Vegetus as well as Bittersweet Vine and pachysandra. Adult males are tiny, narrow and white. Adult females are dark grayish brown, somewhat crescent-shaped and larger than the males. Immature “crawlers” are tiny and orange-yellow.

SYMPTOMS

Scale is a sucking insect with mouthparts like a hypodermic needle. The mouthparts are inserted into leaves and stems to suck plant juices. When the population is high, plants can be weakened to the point of leaf drop. Prolonged infestations reduce plant vigor and death may eventually occur.

A light infestation appears as yellowish or whitish spots on the leaves. However, Euonymus scale is most often discovered by large numbers of the conspicuously white males on upper and lower leaf surfaces and stems of affected plants.

Older plants that are less vigorous are susceptible. Also more likely to be attacked are plants in deep shade, in densely crowded beds, or near buildings where temperatures are high and air circulation is reduced.

LIFE CYCLE

Euonymus scale overwinters as mature “pregnant” females. Eggs are laid under the protective covering of the mother in early spring. The eggs hatch over a period of 2-3 weeks in late spring. These “crawlers” either move to other parts of the host plant or are wind-blown to other susceptible plants.

CONTROL

Because euonymus scale has two distinct life stages, both the adult scale and the immature crawlers require control.

Both adults and crawlers can be controlled by soil drenches containing Imidicloprid found in Bayer Tree & Shrub Systemic Insecticide or Bonide Annual Tree & Shrub Insect Control. It will take 2 seasons for the most effective control, because these products do not kill the eggs. Eggs will hatch, but the crawlers will die as soon as they start sucking the juices of the plant.
Summer Oil or Horticultural Oil is an alternative to the above products.

Keep your shrubs healthy by applying a 2-3” layer of mulch (shredded or chunk bark, coarse compost), watering during dry periods and pruning out dead wood.