Compare with rose midge.

Judging from the photos I could find, I don't think that's what it is. I'll go dig my branch out of the trash and try to get some pictures...

Rose midge fly maggots are usually only found at the very apex of the rose's growing tip.

I believe some kind of moth, beetle, or wasp slit your stems, deposited eggs, or laid eggs on the stems, and the emergent larva ate their way into the stem. The hope that the hatching out larva will live and grow over winter eating the pith of the stem, was cut short when you removed the damaged stem.

I've never had such a case, but if you have no similar damage elsewhere in your roses, be thankful. You nipped it in the bud!

You know, fall cicadas do that kind of damage up in trees at this time of year. The female cicada puts a slit in a tree's outer most twig, lays an egg in the slit, and goes to the next twig. The egg hatches, eats the pith, and the twig above the damage wilts, dries up and dies. The larva drops to the ground, burrows in and feeds on tree roots.

You may have had a cicada or a cicada like insect do the damage. Leaf Hoppers are related to cicadas.

Moses

It was a fairly good sized section

Evenly spaced damage spots

The creatures/eggs? Inside the stem

Thank you, Moses. I believe you're right. I hope this nipped it in the bud! If these things got to my whole bush, it would be devastating.

Dillybeansown,

One good thing is that the damage sticks out like a sore thumb in the garden. You have evidently disrupted the insect's life cycle in the stem you removed.

If it should recur elsewhere, carefully remove the damaged stem well below the damage, as you have done, and have a plastic bag handy in which to place it. Try not to let any grubs drop off, onto the ground. Wrap securely and place in household trash.

I hope someone who has had the same insect damage you have had responds to your post.

Moses

Thank you, Patty! I'm glad to know what they are!

Finally found this again! I've got some damage on my Enchanted Autumn that looks like this, but smaller 'chewed on' areas. Dilly, did yours start smaller and get bigger? I just hate to cut off that cane - poor 'Autumn' didn't get planted as soon as it should have and got powdery mildew, but that new cane looks perfect!

Except for whatever bug decided to chew on it.

Ac if the leaves on rose are fine and the tip of the cane is not wilted you can wait to prune the damage. Just wait until winter sets in or very early spring. So you can kill them before they hatch.

You have just described Raspberry Horntail Wasp damage. It is not uncommon to see young rose canes damaged in this way.

Thanks Patty and Paul! Do these have the potential to become a bloom-stopping, plant-killing infestation, or are they more a here-and-there damage insect? I'm wondering if I shouldn't mark the cane now to remember to get it in the early spring.