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While I was out gardening, I saw a wasp fly through a small hole beside my basement window and into my basement. Then later, I saw five more enter through two other holes (two in part of my AC, three in my fireplace exhaust area.)

The exhaust area looks like this, but with four small holes in the metal plates where it attaches to the wall. That's where the wasps go in.

enter image description here

I taped up the basement hole as a temporary stop-gap. My questions are:

  • What should I use as a permanent seal?
  • Should I seal all the wasp entrance holes?

More importantly, what do they want and how do I get rid of them? I assume there's something in the house (food or a nest) that they're after. I can't find it, and don't know how to look for it.

I would like prevention (no more wasps coming) over protection (spraying all the entrance holes with bug killer) if possible.

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migrated from gardening.stackexchange.com May 25 '12 at 21:35

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is it actually in your basement, or did it just go into the hole? if it just went into the hole, it's probably a carpenter bee. they're good pollinators, and you may not want them dead. –  baka May 25 '12 at 12:24
    
I'm not sure @baka, I'm pretty sure I saw it go into the basement. –  ashes999 May 25 '12 at 13:01
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@baka - the problem with carpenter bees is they can do a great deal of damage to your home. And the longer you leave them there, they will multiply and spread to other spots. –  user558 May 25 '12 at 18:42
    
I suspect wasps. –  ashes999 May 25 '12 at 20:38
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3 Answers 3

It MAY have been a carpenter bee. They look like big bumble bees, and are good to pollinate plants. However they will do a great deal of damage with the galleries they build, gradually eating away a lot of wood. Don't let them get a foothold or you will truly see a great deal of damage done.

A carpenter bee will drill a hole that is perfectly circular. They like cedar, and go for places like fascia boards and soffits. Then they turn, and will drill galleries just under the surface of the wood.

A symptom of carpenter bees is that you have woodpeckers hammering on your house. They will find the galleries, and can hear the echo as they tap against a hollow spot.

If it looked like a wasp, then it still has a nest there. A wasp will not just wander into a hole. It has a reason to go in there.

No matter what it is, I would suggest dusting the hole with an insecticide. (Delta Dust seems to work well for me. I use a bulb to inject the dust into a hole. Carpenter bees are not aggressive, but then stand well back, in case these are more aggressive wasps or hornets.)

If you find carpenter bees tumbling from the nest, wait until they are all dead. The last nest I got rid of had 15 (LARGE) bees in it. I had to repeatedly dust it until they all were dead. Then you need to clean out the galleries (I use a Rotozip tool for this) and fill them with caulk or Bondo, as otherwise the bees will just re-inhabit next year. And if you just fill the entrance hole, a hungry woodpecker may still find that nest.

Once you manage to eradicate the nest, yearly spraying will prevent them from building new nests. They will just find other places to live, NOT in your home.

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Now I'm really confused. There is precisely a circular (though not perfectly circular) hole in the wood. I saw another one enter through a different hole in a metal box connecting my AC; it looked like a wasp, not a bee. How can I locate the nest? What do I do about the holes? –  ashes999 May 25 '12 at 20:28
    
Ok. So if there is a perfectly circular hole, it is carpenter bees in there. But there is also a wasp nest, which you may or may not choose to do something about. Wasps are common. The carpenter bee nest is best dealt with as I describe. We had an pest control person come in once for carpenter bees, and that was a waste of money. Carpenter bees are not aggressive, but they are hungry buggers. As I said, dust the nest to get them out. Once empty, I use a rotozip tool to open up the nest. It is shallow. Then fill with a paintable caulk or bondo. –  user558 May 25 '12 at 21:42
    
Again, how do I find the nests? I've looked inside and out, and I don't see anything. It may be inside my fireplace exhaust, that's where the wasps are going. –  ashes999 May 25 '12 at 21:46
    
It looks like this image, but with four holes in the corners where it sticks to the wall, where the wasps go: nachi.org/forum/attachments/f20/… –  ashes999 May 25 '12 at 21:51
    
That will be a wasp nest in there, probably a paper wasp. They will find a dry spot out of the rain. If you can get some wasp spray into it, do that. If not, then just leave it alone. It depends on how much you want them gone. It won't be a large nest. –  user558 May 25 '12 at 22:32
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Get a product like HotShot for killing wasps. Foam up the mouth of the nest. It will likely finish the job.

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I don't think there IS a nest. –  ashes999 May 25 '12 at 1:55
    
Then get something to patch it closed. Otherwise it is a temptation for other nasty bugs to take up residence. –  ncmathsadist May 25 '12 at 1:57
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"I don't think there IS a nest." = then I'd suggest using a shoe. –  DA01 May 25 '12 at 3:36
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@ashes999 - "I don't think there is a nest" - yeah, right. A wasp is not flying directly up to a hole, then going in without a nest being there. Closing your eyes will not make it disappear. –  user558 May 25 '12 at 10:29
    
@woodchips it may have been a bee. I did not get a good look at it. –  ashes999 May 25 '12 at 13:01
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(I would have made this as a comment but I don't think I CAN comment)

Regarding where the nest might be - how thick is the wall? If there is more than just that brick layer then the nest might be inside the wall. It might not be very big. They can make a nest anywhere they can get to. I would say that if there are wasps (or bees, or whatever), and multiple of them, going into small holes, then there would be a nest of some description. If they were searching for food they'd be doing it out in the open. The way you describe it, it sounds like they know where they're going, so they're probably going home.

There are many types of wasps, so could you describe it at all? This may help identify it and thus what kind of nest it might be making, if any.

If you seal the holes with some kind of filler (anything really that won't wash away) then the wasps won't be able to get in or out and the ones in the nest (if there is one) will eventually die of hunger. Assuming they are in the wall and there isn't a way out into the basement, in which case that might not be so good.

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If you ever want to make it a comment, before you have access, just keep it short (500 characters or so) and hit the flag link to get the mods attention. They can move it for you. –  BMitch Jun 21 '12 at 13:02
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