Euonymus scale is one of the most damaging scales in our area. It can cause defoliation and even the death of many Euonymus. These scales can also affect a groundcover called Pachysandra. Euonymus scales are small (1/8th inch) insects with sucking mouthparts that drain sap from plants, yellowing the front of the leaf. The entire back of a leaf can turn white from the male scales during a heavy infestation. If the scales are sparse, you probably don’t have to treat them unless they’ve been a perennial problem. Natural enemies will control small populations. Variegated varieties of Euonymus are often more susceptible.
Scales overwinter as pregnant females and can produce up to three generations a year in Kansas. The adults have a hard waxy coating that makes them almost impossible to kill with insecticides. The best opportunity for control is when there their young hatch as crawlers. Many pesticides provide good control at this stage, including Hi-yield 38 Plus, Hi-yield Bug Blaster Bifenthrin 2.4, Bonide All-season Oil, and Bonide Systemic Insect Control. Any pesticide you use will have to be sprayed 3 to 4 times ten days apart from May to June when the “crawlers” or immature scales are still active and moving. Repeat this in late August to early September when the second generation hatches. During the winter, you can spray horticultural oil to suffocate the females. Bonide’s All-Season Oil works well during this time of the year.
*Always read and follow label instructions.