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Problem: Euonymus Scale - Unaspis euonymi
Hosts: Euonymus, camellia. boxwood, bittersweet, daphne, eugenia, English ivy, hibiscus, holly jasmine, privet, honeysuckle, olive, pachysandra and stonefruits (Prunus sp.) are reported hosts of this scale.
Description: Heavy infestations are clearly visible from some distance away. Affected foliage appears to have small white cottony spots. Leaves eventually turn yellow and die as feeding continues. Males are white and elongated and females are brown and oval shaped and about 1/16 inch long. Large numbers congregate on the undersides of leaves, twigs, and stems. About 60 days are required to complete a generation. There may be two generations per year.
In the spring, overwintering females lay eggs that hatch in late May or early June. This period usually occurs when fringetrees, (Chionanthus), cockspur hawthorn (Crataequs crusgalli), Beautybush (Kolkwitzia) and Late Lilac (Syringa villosa) are in bloom. Crawlers move to leaves and stem and begin to feed by sucking plant juices. Maturing males prefer leaves and females congregate on stems.
Recommendations:
Prune heavily infested branches to the soil surface. A dormant spray in early spring before the buds have started to open will decrease the scale population but also may defoliate the plant. New leaves will rapidly replace those lost. Apply labeled insecticides such as carbaryl (Sevin), malathion or acephate (Hi-Yield Acephate or Ortho Systemic Insect Control) to control crawlers in late May or early June. Reapply as needed in late August to early September to control second generation crawlers.
Control is probably impossible for Euonymus that has been heavily attacked and is in
very poor health. Therefore, complete removal and destruction of the infested plants
(including roots) is suggested.
References:
1. Insects and Mites Associated With Shade Trees and Woody Ornamentals, pg 24, K-State Research and Extension Pub S-85
2. Life Histories of Common Insects, Mites and Nematodes Infesting Ornamental Plants in Missouri, Missouri Department of Agriculture, pg D-13
3. Euonymus Scale, Horticulture Solutions Series, University of Illinois
4. Euonymus Insects, http://lep.cl.msu.edu/msueimp/htdoc/mod03/01700387.html
Last Update: 08/30/2004
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