My wife and I had a new deck and sunroom installed a little over a year ago. In and near this same spot (and just this spot), off and on, this "residue" accumulates, sometimes a little, sometimes A LOT. This is the most I've seen and the little black "rods" look like some sort of fecal matter (poop).

I see no signs of damage to the pressure-treated wood anywhere, or the sunroom roof above, and the decking is TREX (artificial). Any ideas? We have a subscription with a pest control service, so I can always call them in, but I'm a bit perplexed.

Thanks!

Looks like mouse shit and mouse nesting material

It does look like mouse shit in with the debris, but the apparent location doesn't make sense.
Look for a hole on the underside of the top rail; possibly a carpenter bee?

Is the eave of the sunroom or house above it?

Carpenter bee…look under the rail above.

I'd suspect a carpenter bee, too. Look directly above the debris.

Carpenter bee.
Look harder

Yep. Carpenter bee. I used to occasionally get them in the wood deck at my last house.

Look directly above that pile for a hole (or holes) about the width of your fingertip. Could look like a purposely drilled hole from construction, which might be why you overlooked it before.

Thanks folks. Yes, there IS a hole in the rail but looked so symmetrical it looked man-made. I sprayed wasp spray into it like 6 months ago and I guess it got quieter, but it was also colder months. Makes sense it would get more active with warmer weather.

I'm just amazed at the amount of "stuff" that came out. Do they do a lot of damage. The affected area is under the eave of the roof that extends above the landing to the door.

Should I spray with wasp spray. Let it dry, and fill with some sort of sealant?

quote:

Originally posted by Batty67:
Do they do a lot of damage. The affected area is under the eave of the roof that extends above the landing to the door.

They can. The nest tunnel can extend many inches back into the wood. But if the wood still seems solid then I wouldn't worry too much about it. My handful of carpenter bees over the years never caused any actual structural damage.

quote:

Should I spray with wasp spray. Let it dry, and fill with some sort of sealant?

You can either call in your pest company, or just fill the hole(s) near dusk with a foaming wasp spray that also kills returning insects, like Ortho Home Defense Hornet and Wasp Killer. (That way, you either kill them right off the bat, or when they try to cross the remaining chemical.)

That always took care of them on my deck, until a new one would return a few years later in a different spot.

I never bothered to fill the leftover holes in my deck, and a bee never took over a prexisting hole from what I could tell. But if you wanted to patch the opening, it would be simple to do with a bit of exterior wood putty.

What you want to do is wait until it's dark and they are inside the hole, then fill the hole with caulk. No need to use any sort of pesticide at all.

If you do it when it's light out and they are outside the nest, they will literally remove the caulk from the hole. But once they are inside and it's dark out, the hole always stays plugged. I theorize that they literally go to sleep, never wake up and die because the caulk keeps the light out. Trust me, this works and you know it works because the hole remains filled. And no other insect will take up residence in the hole either if you plug it this way.

Cotton balls soaked in rubbing alcohol work too

Carpenter bees make tunnels in the wood. I doubt you would reach them with any bug spray.

Look up Delta Dust. There are several manufacturers. Its a fine powder you puff into the hole and the bees will track it deep inside and spread it around.

Carpenter bees.... and the tunnels that they bore are not just straight in.......they can snake around zig zaging .....even multible bore holes near each other but never entering the other tunnels... Wait till nighttime and physically plug the entrance holes so the little bees will be trapped inside their tunnels.................. drill sgt.

I had them this spring for the first time. They were buzzing around the deck but there is also some wood piled nearby.

Either way, I didn't want them around so I ordered a trap from amazon that is basically a box w/ an entrance for them on each side. Once inside, they drop down through the bottom into a Ball jar where they can't navigate out.

Once the trap arrived I noticed no more carpenter bees were flying around so I haven't caught any. I read they are most active in the spring so I don't know where they went. I think their larva hatch in the fall?

Well this explains it: https://bestbeebrothers.com/pa...e-of-a-carpenter-bee
I won't be able to trap them again until Aug/Sept.

Probably the only carpenter around that can cut a perfect hole in wood without out tools and gets in trouble for it .

I have filled the holes with roofing tar, they don't remove that.

but caulk is cleaner.

Make some traps
https://www.bobvila.com/articl...-carpenter-bee-trap/

Thanks all for the replies and suggestions. Fascinating. I'll be sure to take care of this soon.

I'd do the trap instead of straight killing them. They're actually extremely beneficial. Once trapped you can release it somewhere wooded.