Euonymus scale is an armored scale that can cause complete defoliation and even death of evergreen Euonymus. They can be found on various other landscape plants. In general plants growing close to buildings are often more susceptible to damage because there is less air circulation and more moisture stress on the plants. The scale is small, only 1/8 inch long. They may go unnoticed. The first signs are a plant that looks yellow or sick. If you look close you may see white, oyster shaped scales on the leaves and stems. If you run your finger over the scales, you can tell if they are dead or alive. Dead scales will be hollow and fall off. Live scales will be attached tight and wet underneath. They over winter under the shell and in the spring females lay eggs. Small insects called crawlers will hatch and move to other parts of the plant or may be carried by wind to nearby plants. In a few days they will begin forming their protective scale and lose their legs.
The best defense against scale is to keep the plants as stress free as possible by watering and fertilizing as needed. There are natural enemies of scale that can help control. Infected branches can be removed or the scale can be scraped or brushed off. Superior-type horticultural oil sprays can be used for controlling scale. The oils will suffocate the scale insects. Check the label for time to spray the plants. For more information on scale control contact your county Extension office, the Master Gardener hotline or local nursery.