by Paulette Mouchet
Originally published in "The Rose Garden" newsletter, May 2003.
Did you know that the cane borer insect is a beneficial insect? But wait! you say. How can it be beneficial to have holes in my canes? The holes are caused by predatory wasps who collect aphids to feed their young. The more aphids in your garden, the more wasps, the more holes in your rose canes.
What happens is the female wasp chews a hole into a cane, stuffs it with aphids (or flies, depending on the particular variety of wasp), lays a single egg on top of the fresh meat, then seals the chamber. She makes additional chambers, one on top of the other until she gets to the top of the cane. The larvae hatch and eat the lovely aphids that mama left for them. They pupate and become adult wasps that leave the cane to start the cycle over again. The larvae and pupae do not damage the rose cane-it's all mama wasp's fault.
The way to get rid of holes in your canes is to control the aphid population. Wash aphids off with a strong blast from the hose. They die before they can crawl back up to feed. Release ladybugs and lacewings, and encourage the birds to help you out.