Scale on my pachysandra
Dormant oils are effective on the overwintering stage of most species, but they can only be applied in early spring before leaves appear. Adult scales are protected from insecticides by waxy coverings. Control measures, therefore, must be aimed at unprotected immature's (crawlers) or the overwintering stage. During the summer, control requires accurate identification of the pest species so that hatching dates of crawlers can be determined. Once the pest is identified and proper timing known, any one of several common insecticides can be used.
Types of Scales: Scale insects can be roughly divided into two groups: armored scales and soft scales. Armored scales are so named because they secrete a protective cover over their bodies. Most species overwinter as eggs beneath the female cover. In spring, eggs hatch into tiny mobile crawlers, which migrate to new feeding sites. After a few days, crawlers settle, insert their mouthparts, and begin feeding. Soon they secrete a protective cover and lose their legs. Large populations can build up unnoticed before plants begin to show visible symptoms. It is important to have the type of scale identified so you will know the month and time to spray with dormant oils to be sure to catch the crawlers. If you would like to send a picture I can try to id the type of scale you are having problems with.
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From the pictures you sent it looks like Euonymus scale.
Scale control requires a certain amount of vigilance. As with many insect problems, stressed plants are more susceptible to attack than healthy plants. Therefore keeping plants healthy with proper watering and fertilizing will help. Prune out branches heavily infested with scale to quickly reduce the population. Many of the scales are susceptible to a variety of parasitoids and predators, including lady beetles, green lacewing, and predatory mites. However, beneficials generally can't control a large infestation.
One method of scouting for scale crawlers is to wrap a piece of black electrician's tape around a branch with the sticky side out. Crawlers will get stuck on the tape as they try to crawl across it.
You can spray with Dormant oil in early Spring before new growth begins.