Euonymus scale (Unaspis euonymi) is a pest that is around all year, especially on groundcover euonymus. Treatment should be done when the crawlers emerge, which is around the early part of June, although it may be a bit later this year. Male adult scales are white, and females are dark brown and are shaped like an oyster shell. Euonymus scale overwinters as a mated (pregnant) female on the plant stems. Eggs develop beneath the scale and hatch during late spring.
Hatch times coincide with the blooming of:
- Chionanthus virginicus – White Fringe Tree
- Crataegus crus–galli – Cockspur Hawthorn
- Cornus alternifolia – Alternateleaf Dogwood
- Syringa vilrosa – Lilac
- Catalpa speciosa
Management: Pesticides won’t help until the crawlers emerge, but if the population is heavy now, prune out the infested branches to reduce the number of scales. Then, when it is time to use an insecticide it will be more effective. Since there has been a lot of winter damage on ground cover euonymus, pruning will be required to remove the dead branches and take care of two problems at the same time.
Horticulture soap* or oil will work to kill the crawlers.
*Please remember that you can’t make horticulture soap out of today’s dish soaps. Yes, back in the day, when soap was manufactured out of fats, it could be done. However, now they are all detergents, lacking the fat factor necessary to kill the insect.
© The Naturarian