How to Kill Mason Bee Larvae in a House Wall

More than 150 species of mason bees live in North America. If you have a nest living in one of your house walls, you’ll notice the hole they use to get inside is plugged with mud. While they are excellent pollinators, having them live inside your home exposes you to the risk of stings and structural damage.

Things You'll Need

• Protective glasses
• Bee veil
• Gloves
• Broad spectrum insecticide
• Screwdriver

Instructions

1. Locate the bees’ entrance into the wall. Look for a small hole, caked with mud around the edges. Mason bees seal off their nests with a mixture of mud and saliva.

2. Watch the entrance for an hour or so and observe the number of bees coming in and out.

3. Count the bees coming in and out. Mason bees have individual nests, not hives. If only a few are using the wall as a nest, you are dealing with mason bees and can kill them and their larvae on your own.

4. Put on protective glasses, gloves and a bee veil to protect yourself from stings.

5. Clear away the mud blocking the hole with the end of the screwdriver to improve your access.

6. Spray the insecticide into the wall. Apply it a few times, waiting an hour in between each application. This increases your chances of killing any adults out gathering nectar. The insecticide will eliminate adult bees, neophytes and larvae.

Tips & Warnings

• Seal the hole in the exterior wall to prevent new bees from moving into the old nests. Something as simple as a small section of window screen will keep them out.

• Keep children and pets away when working with an insecticidal spray. If you see many bees flying in and out of the wall, contact a professional bee removal service. A hive is likely to be honey bees rather than mason bees. Killing them inside the walls can lead to an unpleasant smell as well as wood rot.

References

• Bees, Wasp and Ants; Eric Grissell
• Residential, Industrial and Institutional Pest Control; Pat O’connor-marer