This is an outside wall behind the insulation. I'm about to re-insulate and close the wall up, but I want to take care of any last problems before they become big problems.
Anyone know what caused this???
Most likely it is termite damage, though there are a few critters that will make that kind of mess. As long as the area is not active and not structurally weakened, you don't necessarily have to treat or repair it. If it is active, then you'll want to address both the critter and the damage. An active infestation will be accompanied by larva or mature critters, if you can get to the sub area, termites leave mud tubules from the ground to the infestation so if you remove them and check back a few days later and they're back, you know it's active. Regardless of being active, it's a good thing to clear the tubules and the sub area of any cellulose or wood debris. Termites are attracted by earth/wood contact. They live in the ground and come up for food.
Could have been carpenter ant infestation at one time.
Thanks for the replies!
I thought of both of these possibilities. I looked up termite damage on google, but none of the images looked like this. I didn't look up ant damage images. If it is one of these, is there anything i need to do to keep them from coming back?
If it were me , and this is just my opinion , I would take a scraper and a Shop-Vac and clean all of the residue from the wall cavity . IF no insects are found , I would treat the area with some kind of insecticide and finish the project . Have a pest control company come out and check the rest of your home for Termites , etc .
Odds are that this occurred because there was adequate/excess moisture present to make the wood accessible/inviting to the critters....although there are some insects that will devour/bore dry wood.
I would look hard to find the source of that moisture; poorly done or totally lacking flashing around doors or windows, splits in the siding or shingles, etc.
It is also possible that this moisture accumulated/condensed against the backside of the exterior sheathing (I think that's what we're looking at) because of high interior moisture (RH) during the winter heating months.......which was able to migrate thru the wall cavities. Impossible to say from here and you didn't state your locale, age of house, etc.
You could (I would) use boric acid as a treatment or better yet, set up boric acid bait stations. The latter would give you the best shot at getting rid of the whole colony. You can Google your way to info about how to set up these bait stations.