There were a few larger gaps so i decided to fill them in with other stones.
Yellow jackets in retaining wall.
Pyrethrum aerosol sprays such as pt 565 plus cv 80d or cb 80 extra work well to kill yellow jackets and break up their nests.
Simply cut the bottle in half fill the lower half with sugar water and place the upper half upside down inside the remaining lower half.
Spray the pyrethrum in the cavity where the yellow jackets are living.
This will not only prevent wasps from escaping a pesticide application only to return later but it will also keep the wasps from exiting the nest by another hole to attack or to flee into other parts of the home garage and attic while the treatment is being applied.
I am not 100 sure they are yellow jackets but i believe they are.
The yellow jackets can actually use the drywall for nest material leaving only a layer of paint between their nest and your living space.
Seal off any entrances or exits into the area of the wall where the wasp nest is located.
I have a sandstone retaining wall.
To kill a yellow jacket start by putting a small piece of fruit or a sugary drink inside a sealable jar or soda bottle since yellow jackets are attracted to sweets.
Then wait for the yellow jacket to land seal the jar or bottle and dispose of it safely.
They will come out in the spring looking to go outside.
Find the area where the noise is the loudest either by placing your ear against the wall or using a listening device.
If the nest is in a very warm location however the whole nest could survive the winter.
If a do it yourself treatment is done wrong the consequence is a house full of wasps.
Use caulk or a similar sealant.
They ll die on contact.
You may also be able to hear the yellow jackets moving inside the walls.
If yellow jackets have gone into the walls during cold weather some of the reproductive yellow jackets may survive in the walls.
Yellow jackets in retaining wall.
The ideal time to get rid of yellow jackets from the wall cavities would be night time or early morning.
When i put the first stone in about 15 bees yellow jackets came out.
I used 4 cans of bee killer and they are still all over the place.
Follow up the spraying by dusting the opening of the nest with an insecticide such as tempo dust.
Press down firmly and seal off the outer edge with tape so that it is airtight.