Key to Euonymus
Plants in the genus Euonymus are fairly common in Southern landscapes, although only about 220,000 are produced by nurserymen each year. Because of its varied leaf size, color, and form and its varied growth pattern, euonymus can be used in many situations.
Several scales, the Japanese weevil, and spider mites have been reported on euonymus in the Southeast. The most important pest of euonymus is the euonymus scale.
- Euonymus scale – Chlorotic spots appear on the leaves; tiny, brown and white scales mark leaves and stems.
Euonymus scale, Unaspis enonymi (Comstock), Diaspididae, HEMIPTERA
Adult – Elongate (.75 mm) and white, the mature male is a tiny, two-winged insect. The female is 1.5 mm long, dark, and shaped like an oyster shell (Figure U).
Egg – The tiny egg is yellow and oval.
Crawler – The crawler is also tiny and yellow.
Distribution – Euonymus scale is the most commonly reported pest of Euonymus, Pachysandra, and Celastrus throughout the Southeast. Although this scale is small, infestations are often dense and plainly visible.
Host Plants – Euonymus, Pachysandra, Celastrus, ivy growing near Euonymus Camellia, twinberry, eugenia, and hollies are the known hosts of the euonymus scale.
Damage – The first visible damage is yellow spotting on the leaves. The stems may become so encrusted with the scales that whole branches or the entire plant dies.
Life History – This scale usually has two or three generations per year. The males emerge as tiny, twowinged flies and mate with the females, which shrivel as they lay eggs under their protective shells. The tiny crawlers hatch and emerge from the mother's shell in April, May, and June; female adult euonymus scales do not leave the protective covering. The crawlers move along the leaves and stems before inserting their sucking mouthparts to feed. They then secrete their protective covering. Another brood hatches in late summer, and a partial third brood may appear even later. As a result, all stages of development are present most of the year. Males are usually more numerous than females, in dense infestations, clusters of the snow-white males on the leaves and twigs are clearly noticeable.
Euonymus scale is difficult to control, but the removal of heavily infested branches will help. For specific chemical controls, see the current state extension recommendations.
Publication date: Jan. 1, 1993
Other Publications in Insect and Related Pests of Shrubs
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