The crawler stage (young scale that have recently hatched) is when euonymus scale is most easily controlled. Therefore, check to be sure crawlers are present before treating. Since there are multiple generations per year, check for crawlers now. Spraying when crawlers are not present is ineffective. Double-sided tape or electrical tape smeared with petroleum jelly can be used to capture crawlers making them more easily seen. Use a magnifying lens to identify the very small crawlers. If nothing is moving, crawlers are not active yet.
Labeled insecticides that are effective for the crawlers include malathion and acephate (Hi-Yield Acephate or Ortho Systemic Insect Killer), permethrin (Hi-Yield 38 Plus Turf Termite and Ornamental Insect Control, Hi-Yield Indoor/Outdoor Broad Use Insecticide and Lawn & Garden Insect Killer, Fertilome Indoor\Outdoor Multi-Purpose Insect Spray) or cyhalothrin (Spectracide Triazicide, Bonide Caterpillar Killer).
Dormant oil can also be used for control in February to March to control overwintering scale. Temperatures need to be at least 40 degrees so the spray has a chance to dry before freezing.
Overwintering females lay eggs that hatch in mid- to late- May or early June for the first generation. This period usually occurs when fringetrees, (Chionanthus spp.), cockspur hawthorn (Crataequs crusgalli), Beautybush (Kolkwitzia amabilis) and Late Lilac (Syringa villosa) are in bloom. Crawlers move to leaves and stems and begin to feed by sucking plant juices. Maturing males prefer leaves and females congregate on stems.
Control is probably impossible for euonymus that has been heavily attacked and is in very poor health. Therefore, complete removal and destruction of these heavily infested plants (including roots) is suggested. (Ward Upham)