I would poke and see how much damage there is to the bud union. I would bet not much. Sometimes the graft or crown swelling will eventually grow out around the base of an old cane, so that a socket is left where the base of the cane rotted or was drilled out. The graft is solid wood, unlike the cane pith that the borers eat.

The culprit might be the rose (raspberry) stem borer, a sawfly that lays eggs in soft growth tips in midsummer. The egg develops into a white segmented worm that eats its way down and grows to a length of 1". Watch for wilted growth tips during the second flush of growth. Squeeze suspicious stems for hollowness. This pest is not related to the little bees and wasps that nest in cut cane ends and are relatively harmless.

I've had this same situation and the rose was fine. I think the graft union was big enough that the little hole from the borer didn't really affect it much. This year cover all cut ends of your canes with some glue or nail polish and you should be able to prevent the problem.

I use elmers glue on the ends of pruned canes.

Lime Sulphur spray is labeled to eradicate cane borers. If your roses are still dormant (and I would bet they are in your zone) douse 'em with spray at the dormant strength. If they are growing, there is another, lesser strength to use for growing plants. The difference is that the lime sulphur spray will burn off any growing leaves the next time the sun warms them up.

Sealing the ends of the canes with Elmers Glue (which has to be reapplied if it washes off) or nail polish (which is permanent) will prevent it from happening again this year.

Good luck,
Kathy

Oh, I never knew that Elmers glue would have to be reapplied if washed off! Maybe I should also be using nail polish!

Cathy

If you have a borer running way down the cane, (to repeat) it is not the type that enters in cut cane ends, so sealing will have no effect. It begins with eggs laid near the top of soft growing stems. I have dealt with both types for decades. Frankly I don't worry about the cane ends, because the damage is usually shallow and sealing is such a nuisance. Probably most people who keep a lot of roses do not bother to seal. I do scout for wilted growth tips in season and kill the worms, usually a few per year.

I agree with Michael. Those borers don't have to enter on the tips, anyway.

Sammy

I am in rain country and the Elmers doesn't wash off the ends..

The only borers that I have are the kind that enter the cut ends, and they do go quite a ways down into the cane. They get into the rose canes, raspberry canes, and even my grape has a hole in the cut end. Once I started sealing the ends my problem wasn't nearly as bad and mostly only the canes that are cut later in the year and I forget to seal have the problems. The grape vine was cut by a rabbit and I haven't managed to teach them to seal the ends. So I would say that whether or not sealing works depends on the type of borer you are dealing with. I switched to the Elmer's carpenters glue which is supposed to be more water resistant, but the plain kind worked fine for me too.

Regarding the cane borers: They start at the cut cane: rose, grape, nine bark, etc. Whatever the cane, that is where they start. You prevent their entrance by sealing the cut end--this doesn't taste like fresh-cut wood! Lots of things will seal the ends of canes. I like white carpenter's glue, because it is easy to dispense and easy to clean up. However, I have a teflon-based fingernail polish in my tool belt that I have used very successfully to deter these critters!

Regarding re-applying: If the glue was able to skin-over before the rains, it will remain and provide the protection. But if the rain washed it off, of course you will have to reapply.

Related subject: We have always "followed the cane borer" down the cane. Cutting off the cane until we no longer had a hole. We have never used cane-borer killer sprays, although that is an interesting option. Our motto has always been to 1) prevent cane borers from finding a home and 2) cut them out, even if it was very low in the plant.