Roses

Question

What are white spots on my rose bushes….

Answer 1

There are white spots caused by powdery mildew and whitish gray spots on leaves caused by insects, often eating on the underside of the leaves. Where I live, this is the time of year when rose slugs are active. They aren't true slugs but the larvae of sawflies. They either burrow into buds to eat, which destroys them, or they suck the juices out of leaves leaving a white spot that eventually becomes a hole. Rose slugs when young are 1/8" long and yellow-green. Their maximum size is 3/4". Unless the infestation is severe, remove them by hand. There are usually 2-3 generations per growing season so keep an eye out for them to recur.