Blue/Black wasp under our pool deck. How do I get rid of them when I can't see the nest?

So we have an inground pool with a wooden wrap around deck.  These humongous black wasps with a bluish sheen fly around and are everywhere out there. We see them carrying grasshoppers and taking them between the wooden slats under the deck.  We abandoned our pool early in the season because they are very aggressive. Obviously if we are out there we are swimming, walking on the deck, jumping, playing music and what not.  This appears to annoy them.  I cannot see any nests but there must be several down there because they go in all over the place.  Help.  What can I do to get rid of them so they don't come back next year?

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You can significantly cut down on the population by hanging fly paper strips around where they enter and exit the deck. That is how I safely reduced a colony of ~5,000 yellowjackets down to a dozen. We had an enormous hornet nest in a large storage box at the top of the stairs in an outbuilding one year. By the time we noticed, they had the capability to sting someone to death, were easily irritated, and were in a location that couldn't be sprayed without either also covering yourself in pesticides or trapping yourself in an attic with thousands of angry hornets. I think I used 10-15 strips in total. When they were covered with dead hornets, I'd hang a fresh batch.
those things couldnt have been yellowjackets, sir. yellowjackets live in holes in the ground, not boxes.
I know my Pacific Northwest bees and wasps. Yellowjackets often nest in the ground, preferably in an old rotten log or big pile of mulch, but any enclosed cavity will do. The box was full of stuffed animals which were chewed up and incorporated into their nest.

They also get into attics and house walls and nest in the insulation.

Baldfaced hornets (black+gray) and paper wasps (yellow+black or brown) are the ones that make a basket ball-shaped nest in a bush or tree.

There are also a number of solitary gregarious ground nesting species such as sand wasps that will nest in a burrow, with each wasp taking care of its own burrow and ignoring its neighbors. They do not defend the colony enmass.
typically what i have heard of people doing is pouring gas down the hole and torching it. i cannot attest to the effectivess of that though, since ive never seen it done. also may be some explosion/burn risk if you do dont use a very long device to set it alight.
Burf6 years ago
Sounds like Mud Daubers to me. As the name implies, they build their nest out of mud they gather. So, they build their nests in dark, warm, dry places and usually in corners or crevices making them hard to find. The nests don't hang open and exposed as do most other wasp and hornet nests do.

At this time of the year, unless they are a real problem I would suggest you wait until there have been several very cold days in a row, killing off the adults. Then crawl under the deck with a high intensity light and check every likely place you can find and break down all the nests you see. That should eliminate the problem next year.

One thing to keep in mind, Mud Daubers feed their larvae spiders of all kinds, including the poisonous varieties, they are beneficial in that respect.
frollard Burf6 years ago
all about the noxious fumes from running vehicle trick :D
It sounds like you got some ground wasps. They can be very agressive when agitated. You need to find where they are going in at adn cap it. What I've done in the past is use a mason jar with a few inches on gas and flip it over on top of the ho;le in the ground. The gas will smother them and the upside down jar will hold them in till they are dead. You need to make sure they don't have more than one exit, or you could be hurting once they get out.
rickharris6 years ago
Expert assistance - unless you willing to risk severe stinging