A few weeks ago, when it was below freezing, another wasp flew in. I certainly do not want to rip open walls unnecessarily, but I am terribly worried that as the weather warms, they will begin to swarm again. How do I determine if they are nested in the walls and whom would I contact to exterminate them if they are?
A: Yellow jackets are scary — and for good reason. Unlike honeybees, each wasp can sting multiple times. And when one wasp goes into attack mode, its nestmates do, too, because attacking yellow jackets release a pheromone that signals to others that they need to defend the nest. People can trigger this attack mode even when they aren’t trying to hurt the wasps. Vibrations, such as from a lawn mower or hedge trimmer, can set them off.
But there are also some yellow jacket facts that might soothe your worries. Where winters are cold, colonies of yellow jacket wasps typically die off once the weather turns. Only the future queens, already inseminated, survive, and they do that by leaving the nest and sheltering in hollow logs or other protected places. Most yellow jacket nests are in the ground or hollow trees, and the old nests just rot away. When the nests are in wall cavities, as in your house, they can be left in place because the old nests aren’t reused and wasp nests don’t contain anything that’s likely to cause much of a stink. Honeybee nests in walls, on the other hand, do need to be removed by opening up the walls because of all the honey stored there. But wasps don’t store honey.
Based on the fact that you live in Maryland, you probably don’t need to do anything to keep wasps from being the same problem this year. Perhaps the one wasp you saw since cold weather set in was a queen-to-be. These sometimes do show up inside homes in winter, but because it’s a lone wasp, a fly swatter or just getting them out of the house will solve the problem. It’s not the same as trying to eradicate a whole nest full of active wasps. If another wasp shows up, save the body and show it to a pest-control expert who can identify whether it is a future queen, which means it is no issue, or a worker or a male, which would be evidence that the nest is still active.
Nests in wall cavities can survive in warm-winter areas, and they occasionally survive even in cold-weather areas when a wall is warm enough. To determine whether you are facing that situation, try putting an ear to the wall or get a stethoscope. Silence is reassuring. But if you hear buzzing within the wall, that’s a sure sign of an active nest.
If the nest is active, call back the same pest-control person or switch to another one. Perhaps the earlier treatments didn’t reach the nest, but by using sound to pinpoint the location, another treatment might be more successful. Besides applying the material from the outside, it might also be possible to go in from the inside by first drilling a small hole in the wall. There should be no need to dismantle the wall, though. You don’t need to remove the nest, just kill any wasps still living there.
Homeowners who aren’t severely allergic to wasp stings can often eradicate a wasp nest in the ground or where it is clearly visible on their own by buying an aerosol can of pesticide labeled as a wasp killer. Spectracide Wasp Hornet Killer ($4.98 at Lowe’s), for example, is designed to shoot up to 27 feet, allowing someone to stand far back from the nest when spraying it. The best times are evening or early morning, when the wasps aren’t active.
It’s best to let a pro deal with a nest hidden in a wall, according to the University of Maryland Extension, which has advice online about identifying and controlling yellow jackets in the state. With a hidden nest, there’s no guarantee of getting the pesticide exactly where it’s needed. If it gets close but not close enough to kill on contact, you could quite literally be stirring up a hornet’s nest, so protective gear is a must. “Do not block a nest entrance hole in a wall of a building,” the advisory states. “Angry yellow jackets can chew through wallboard to escape.”
If the nest is dead, or if you need to do additional work to dispatch it, there is no guarantee another wasp nest won’t form in the walls or in your yard. Wasps forage over a wide area and might show up even if a nest is far away. They also eat other insects, so they can be beneficial overall, but to discourage them from being pests when you are dining outside or your kids are playing outside, limit how much food they can find. Keeping trash cans covered helps a lot.
Have a problem in your home? Send questions to localliving@washpost.com. Put “How To” in the subject line, tell us where you live and try to include a photo.
