Treating Euonymus with Scale
Thanks for any help
Wayne County Michigan trees and shrubs
It sounds like you have done all the right things, but your timing may have been off. You need to spray in the spring when the “crawlers” are out, usually around June (but I would look for them as early as May). To check for crawlers, hold a white sheet of paper under a branch and tap the branch vigorously. The crawlers will fall onto the paper. They are very small, so if you see these small “dots” moving around, then you know they have hatched. That’s the time to spray with the oil treatment. If you don’t catch them at that time, a spray will not work as they exude a waxy substance which covers them and protects them from outside elements. Then the systemic applications would be called for. If you catch the crawlers early, you should be able to avoid the scale from showing up later in the summer.
This is something I copied from a website which is very informative on the subject:
Euonymus scale, Unaspis euonymi, is an armored scale that is a very common pest of euonymus and pachysandra. Although the individual insects are small, infestations are often dense and plainly visible. Euonymus scale is now established in the United States and Canada and has become a major concern in many landscapes. Without treatment, heavy scale infestations will reduce photosynthesisthe process by which plants make "food" for themselves. This process involves sunlight, water and carbon dioxide., stunt plants, cause leaves to fall off, and kill all or part of the plants. Management of euonymus scale with contact insecticides may be difficult because of the waxy covering that protects the insects most of their lives. Newly hatched crawlers are the easiest to control with contact insecticides. Monitoring for scale crawler emergence is important to create an effective management program. Examine individual trees by tapping a branch over a white sheet of paper and looking for crawlers during the period when crawlers are expected. A soil-applied systemic insecticidea chemical compound designed to kill insects, can be either contact (kills on direct contact with the insecticide) or systemic (absorbed within a tree to kill insects when they try to feed on it), is effective for season long control of euonymous scale if applied in the spring. Moving through the plant where the insect feeds, a systemic insecticide eliminates the need for multiple sprays and constant monitoring, making treatment more manageable. Eggs are laid in early spring and hatch in late May or early June. The young nymphs crawl to other parts of the host plant before settling down to begin feeding. Once settled, they secrete their waxy protective covering and produce a second generation by mid-July, and a third generation in October.
Hope this was helpful. Feel free to contact us again if you have further questions.