Yellow jackets in wall...

Wall Void Nest

Yellowjacket nest inside wall void
Sometimes yellowjackets, especially the German yellowjacket, decide to build a nest inside a building rather than outside. Common nest sites include wall voids, drop ceilings, attics, and voids in concrete block. Nests are usually the size of a basketball, but can grow ten times larger. Nests in void spaces are irregularly shaped to fit the void. There are at least three possible scenarios that you could find yourself facing with an indoor nest:

1. You found the entrance hole.
Yellowjackets take advantage of openings on the outside of buildings. They can enter a void through a hole in mortar, space around a window frame, or an opening around a conduit, vent, or exhaust fan. The bad news is that finding the entrance hole doesn't mean you've found the nest. If you're lucky, it may be only a few inches away, but it can be as much as 30 feet from the entrance.

Sometimes you can locate the nest by placing your ear (or a listening device) against a wall and listening for activity.

If you can't find the nest site for a more precise treatment, first use a "quick-freeze" aerosol product to eliminate stirred-up yellowjackets near the entrance. Make sure that the insecticide will not blow out of the void into the room on the opposite wall through electrical outlets, vents, or holes. If the nest is far away, an aerosol may not reach it.

A residual dust will drift further into the void and can be carried back to the nest on the bodies of returning workers. Also, since some of the brood may still emerge days later, a residual in the nest will eliminate these as well. Make sure the dust is labeled for an indoor site. Don't close the entrance hole after treatment. Leave it open so any returning yellowjacket workers will have to pass through the insecticide.

2. You know exactly where the nest is located in the void.
Drill a small hole into the wall or ceiling at the nest site and inject an aerosol or dust directly into the nest. Then seal this drill hole. If you've also found the outside nest entrance, treat that as described in #1 above and leave the entrance hole open.

3. Yellowjackets have emerged inside.
In this worst-case scenario, the yellowjackets have chewed through plasterboard or found some other opening from the void into a room. This happens naturally if the nest grows too big for the void space. It can also happen if a failed insecticide treatment flushes them out of the nest site, particularly if the nest entrance is blocked.

Close off that room if possible. Use a space spray labeled for indoor use to knock down the yellowjackets. Next step is to find out how they're getting into the room. Sometimes, they'll find an existing opening where the floor and wall meet behind molding, or will emerge from a light fixture.

If they've chewed through plasterboard, you should see a soft, wet area around the opening. Before you inject insecticide into this space, you should strengthen the area by putting overlapping strips of masking tape across it to reach solid plasterboard on each side. Then cut a small hole in the tape and inject an aerosol or dust that is labeled for this use. Cover the hole with a final piece of tape and wait a few days before having the plasterboard repaired.

Closeout procedures.
Regardless of which treatment you've done, it's best to wait at least a couple of days before checking for any activity and closing out the job. Decide whether or not the nest should be removed from the void. The decision to remove the nest assumes that you know its precise location. In some cases where plasterboard has to be repaired anyway, the nest is exposed and easily removed.

In most cases, yellowjacket nests in voids don't need to be removed. Consider the following:

1.If the nest is in an unoccupied area like an attic, it would be less likely to cause problems later than if it is in a living space.
2.If the nest is inside cinder block or behind expensive wood paneling, it could be expensive to remove.
3.If the nest has a large number of dead larvae, they could rot and cause an odor problem or attract insects. [A nest treated late in summer or fall will be mostly empty of larvae.]
If the nest is not going to be removed, as a final step inject a long-lasting repellent insecticide into the nest. This will kill any yellowjackets that may still emerge and it will prevent dermestid beetles and other secondary pests from infesting the old nest. Also seal the entrance hole on the outside to prevent a new yellowjacket queen from using the same site in the future.

Wet the area around the entrance. While it's still damp throw sevin dust on the damp area. As the enter they will take it in with them and kill the hive. I've had success with this several times with honey bees

I just taped a no pest strip where they were going in and out, 24 hours later, all dead