Question: My purple plum looks like something ate holes through all of its leaves. What kind of an insect causes that damage?
Answer: No insect in most cases, but a disease. It’s usually the result of bacterial leaf spot that hits in the spring, as the new growth is developing. Use Bordeaux mixture or other copper fungicide in the early winter, just after the leaves have fallen, to stop the over-wintering phase of the disease. Spraying in the growing season could cause leaf burn.