Its that time again....when you go out and find your roses are chewed up pretty thoroughly....holes in the leaves, maybe even entire leaves defoliated.
It's most likely the rose sawfly doing the chewing. If you look on the underside of the leaf you may find a green crawling chewing creature that looks like a caterpillar. It's not technically a caterpillar but is the larva of a (non-stinging) wasp. Anyway, they love rose leaves.
It's not cause for too much alarm, by the time you notice them, most of the life cycle of the insect is ending. And they are almost ready to move on. They will not continue chewing all summer, so not to worry.
What to do now: If you have a few roses you can hand pick them, or spray with a strong jet of water to knock them off. They wont crawl back up, promise. You can use a spray of Neem oil or any commercial product designated for insect control on roses.
Finally, you can prune or shear the worst part of the rose, dispose of the trimmings in the trash, and anticipate lovely new foliage on your rose.
Here are some pretty accurate photos of the insect and the damage:
http://www.sactorose.org/ipm/84rosesawflies.htm
