Q: This year when pruning my roses after blooming I noticed a small hole at the top of the stem. This hole goes back down the stem, which dies back sometimes as much as six inches. Is this caused by a bug or the way I’m pruning?
A: Rose stems are occasionally damaged by rose twig girdlers, small carpenter bees or leafcutter bees. The stem girdler lays eggs on the bark and larvae burrow under it, going around the stem in spiral fashion. A leaf cutter bee or a carpenter bee bores into the soft pith of pruned branches to lay her eggs.
From the evidence, I think either a leafcutter bee or a small carpenter bee is your problem. This is usually not a huge bother for rose growers unless there is a big population of the insects nearby. Since both bees are important pollinators, I do not recommend chemical control. In the future, try sealing pruning cuts with Elmer’s glue, Vaseline ™ or a thumbtack pushed into the cut stub.