Yellowjacket ground nests are a particular kind of yard problem. The nest is underground, the entrance is a small hole that looks like any other hole in the dirt, and the colony is aggressive enough that getting close enough to investigate is an unpleasant proposition. If you’ve had tree stumps removed or any ground disturbance that left multiple holes in the area, you may not even know which hole leads to the nest.

The brick trick solves the identification problem.

Finding the active hole

Yellowjackets are territorial and need clear access to their nest entrance. If you block the entrance, they’ll congregate outside it, trying to get back in. That behavior makes them easy to spot — and it’s how you identify which of several suspicious holes is the active one.

Cover each hole in the area with a brick or a flat stone. One hole at a time, or all of them simultaneously — either approach works. Then step back and watch. Within a few minutes, the yellowjackets that were out foraging will start returning to the nest. They’ll cluster around whichever brick is blocking their entrance, hovering and trying to get under it. That’s your hole.

Mark it, clear the other bricks, and note the colony size from the activity level. A lot of insects clustering indicates a mature colony, which means a larger nest underground and a more substantial treatment job.

What to do about it

Important disclaimer: the video demonstrates using gasoline to treat the nest, which was a common backyard method at the time. Gasoline near a hole in the ground is a fire hazard, and the fumes are toxic. This approach is not recommended and has been superseded by safer, more effective options. Don’t use gasoline.

Effective current approaches:

Dust insecticides designed for yellowjacket ground nests — products like Delta Dust (deltamethrin) or Drione (pyrethrin with silica) — are the professional standard. Apply them at night when the colony is largely inside and inactive. Puff the dust into the entrance hole using an application bulb. The dust coats the interior tunnel and the insects track it through the nest as they move. Colony death typically takes a few days.

Liquid insecticide concentrate applied at night is another approach. Pyrethroid-based products (permethrin, bifenthrin, cyfluthrin) are widely available at hardware stores. Mix to the labeled concentration, pour into the entrance, and cover the hole immediately. The liquid soaks into the nest galleries.

Commercial aerosol wasp and hornet sprays marketed for ground nests work for smaller colonies. The spray can application tip extends into the hole, the product foams on contact to fill the tunnel, and the pyrethroid kills quickly. For large established nests the aerosol volume may not be sufficient to reach the full colony.

In all cases: treat at night, when temperatures are below 50°F if possible (the colony is sluggish), wear protective clothing including long sleeves and a hat, and have an escape route planned. Don’t use a flashlight directly over the hole — reflected light through a hole in the ground can agitate an otherwise-dormant colony.

Gear up regardless of method

Whatever treatment method you use, appropriate protection is worth putting on. Yellowjackets can sting multiple times and are not reluctant to do so when their nest is threatened. At minimum: long pants tucked into socks, long sleeves, and gloves. A beekeeper’s veil or full mesh head protection is useful. Treating in the dark means you’re less visible to the colony, which matters — yellowjackets navigate by sight and are harder to agitate in the dark.

After treatment

Leave the entrance covered with a brick or board for several days after treatment. Foragers returning from outside will have nowhere to land and will disperse. Check during daylight over the next week — if you see active yellowjackets still returning to the entrance area, a second treatment may be needed for a large colony.

Once activity has stopped for several days, the nest is dead. The underground nest structure will decay on its own; yellowjackets don’t reuse old nests, so it doesn’t need to be excavated.

References and further reading

• Managing yellowjackets — UC IPM — University of California integrated pest management guide, with seasonal colony development and treatment timing
• Delta Dust insecticide — label and application — dust application method and safety data