This looks like animal damage. It could be some type of rodent damage such as rats, mice, or voles.  It could also be rabbits, porcupine or squirrels.   All of these critters feed by gnawing on bark or plant crowns. Luckily rabbits and voles are favorite food of many predators such as owls and hawks but winter damage may still occur.

Wire fencing is the most effective protection. Construct cylinders around plants and tree trunks made of hardware cloth with a mesh of no more than 1/4 inch. Bend the bottom six inches of the fence outward at a right angle and bury the bent fence under an inch of soil to discourage digging. The taller the cylinder the better but 3-4 feet tall is usually enough.

Trapping or nocturnal monitoring will help you to identify the culprit.

Repellants can be effective in deterring rabbits but must be used before extensive damage occurs. Repellants are not as effective if pest populations are high and food supply is low. Repellants for voles have not shown consistent results but may be worth a try. Voles can be managed with mouse snap traps baited with peanut butter-oatmeal mixture or apple slices in their runs.

Repellants work as odor and/or taste deterrents. The best repellants contain both. A weekly spray of a homemade mixture of 4 eggs, 2 ounces red pepper sauce and 2 ounces of garlic blended with water to make one quart then strained showed some effectiveness in a Consumer Report study. But who wants to have to spray that every week? Other listed repellants include bags of human hair, bars of soap containing tallow, baby powder and predator urine. All these have had mixed results but don't weather well. The smell of some will keep you out of the garden as well.

Here are some publications you will find useful.

https://extension.oregonstate.edu/news/prevent-hungry-rodents-chewing-trees-shrubs

https://articles.extension.org/pages/42222/rabbits-have-eaten-the-bark-off-of-both-of-our-apple-trees-what-can-we-do-to-save-the-trees

Hope this helps!

Hi Chris. Thank you for your reply. I’m not confident that the problem is rodents, since they have chisel-like incisors and would leave marks in this soft wood. The wood is very smooth with no sign of tooth marks. The lowest damage is at about 2 1/2 feet off the ground, so probably not rabbits. Could it be that the bark is spontaneously separating from the wood for some reason? Would you like more photos?

Here is another possibility I came across:

Hornets. Hornet workers are sometimes noticed collecting from the oozing sap of trees. They have been reported to girdle twigs of numerous trees such as dogwood, birch, rhododendron, and fruit trees, probably more for the sap than for the wood fiber.

European hornets girdle smaller twigs and gnaw holes in the bark of larger branches. The hornets chew off the bark in order to feed on the sap that flows from the wound. Some of the bark fibers may be used for nest construction. Often the portion of the twig above the girdled area dies. Usually before the twig dies it tries to regrow, causing an abnormal swelling above the wound. Although injury becomes most noticeable in the fall, European hornets may have been removing bark and collecting sap for a month or more.

Identification: The European hornet is a stout hornet approximately 1-inch long. The color of the head and thorax is dark reddish brown with deep yellow and brown black markings on the abdomen. The markings on the abdomen are similar to the markings found on yellow jackets. The European hornet resembles the cicada killer wasp but is more robust and has more hair on the thorax and abdomen (but is not as hairy as a bee).

Hymenoptera, Vespidae: Vespa crabro germana

Here is a publication:

https://extension.umd.edu/hgic/topics/european-hornets

 Hope this helps!

Hi Chris. You are the second person to suggest the European hornet. Hmmm, I will have to go outside with a flashlight. So interesting that they fly at night. The damage they do does look similar to what we have.

Thanks for the article. It sounds like they die this time of year, so we may have to search for nests next year. Unfortunately, most of the branches have been girdled so we may lose these large, old shrubs.

Here is an article for you:
https://plant-pest-advisory.rutgers.edu/european-hornet-the-mysterious-branch-girdler/

Debra






here is an article for you.