White powder appearing

A few years ago I had my old garage-type building sprayed with foam insulation--on the inside surfaces, including the roof. Now I'm starting to see little piles of whitish powder on the floor. Above the piles on the ceiling are sometimes seen what might be the entrances to little tunnels. Any idea what this actually is, and what I should do about it? (I'm in northern Michigan.)

Close-up of powder on the floor

Close-up of the ceiling above the pile of powder

 

I would first suspect ants, probably carpenter ants but maybe not, chewing the sprayed-on insulation. Ants love to live in foam insulation. They chew it out for nesting, not eating. Look closely in the piles for ant body parts. If you find that, then that's a confirmation of ants.

In any case, I'd treat directly into those openings with an aerosol can that has an applicator tip, or straw on it. Protect your eyes/face and wear gloves. If there are ants in there, it could get exciting. Assuming you find ants, I would treat with a water based insecticide containing the active ingredient: fipronil. Comes in various brand names such as Termidor, Taurus, Fuse, and others. Insecticide concentrate that you mix with water. Treat exterior perimeter of garage, high and low perimeters, cracks and crevices, etc. Keep us posted with what you find.

 

Thanks PABugman! I ordered some Termidor Foam. We'll see...