Managing Euonymus Scale

White and brown hard bumps shaped like oyster shells on the stems and leaves of euonymus, pachysandra and American bittersweet mean euonymus scale are feeding on your plants.

These pests suck plant juices causing yellow spots on the leaves. As populations build the hard-shelled scales cover the leaves and stems. Their feeding damage can cause leaf drop and branch dieback.

Control small populations by rubbing them off the plant and pruning out infested branches. Severe infestations are difficult to control. The hard shells protect the insects and multiple generations require ongoing management.

You can use organic horticulture oils like Summit® Year-round Spray Oil that kill all stages of this pest. As always, read and follow label directions carefully when using either synthetic or organic pesticides.

A bit more information: Another management option is to treat the immature stage of the scale, called crawlers, right after hatch. They lack the hard shell and are susceptible to organic controls such as insecticidal soap. Then make 3 or 4 more applications at 10- to 12-day intervals. Those in warm climates may need additional treatments between July and September to manage later generations.