I have a euonymus fortunei which is infested with bugs. I apply dormant spray in the spring but the bugs return in the summer and chew the plant. The bugs are small and hard-shelled.

You have euonymus scale. Dormant spray should be applied right now to every fruit tree, rose bush and most flowering shrubs. Temperatures at night are above zero and the buds have not yet broken on most plants. If you spray dormantl spray you will kill overwintering insects and diseases. The oil is the spray you will use throughout the growing season to maintain control over the euonymus scale. It is organic and completely safe to use around children and pets. And it's environmentally friendly.