Paper Wasps. Photo credit: Steve Jacobs, Penn State Department of Entomology
Choosing a Product
For any nest smaller than a grapefruit, homeowners can use a ready-to-use insecticide with a pyrethrin or pyrethroid active ingredient. Looking in the retail stores, you will not have a hard time finding an aerosol can with the word "Wasp" or "Hornet" written on the front.
Also the label on the front will have a signal word. If you find two similar products, and one has a "Caution" signal word and the other has a "Warning" signal word, choose the Caution product. These words indicate how toxic the product is and Caution is the least toxic. Warning is considered moderately toxic while a Danger Poison signal word is extremely poisonous, even to humans. A "Danger" signal word indicates the product will cause a severe eye or skin irritant.
You can check that the active ingredient is a pyrethrin or pyrethroid by seeing if it ends in '-thrin', such as Cyfluthrin, D-trans Allethrin, or Phenothrin. This insecticide class has good knockdown meaning it kills the bugs quickly, which is important when dealing with bugs that fly and sting. Another benefit of using pyrethrins and pyrethroids is that they break down quickly in sunlight and rain, so they are not in the environment for long.
How to Treat
Make sure you have located the nest. Paper wasp nests are grey, often have exposed cells, and are built in sheltered locations. You may see the wasps resting on the nest. Ground nesting yellow jackets may be harder to locate, but the nest will only have one entrance from where you can observe the wasps entering and exiting. Yellow jackets often nest near or under fallen logs, fence posts, or concrete slabs.
One thing you do not need to treat is the nest of mud daubers. These insects are beneficial and almost never sting. Mud dauber nests can be removed by knocking them down with a long pole like a broom handle; no chemicals are necessary.
Once you have located the problem nest, wait until the evening or early morning to do the treatment. Treating during the heat of the day is more difficult because the wasps are at their most active and some of the colony members will be out foraging. You want to treat when all the bugs are "home." Read the label instructions on the product you purchased and apply exactly as directed. You should consider wearing rubber gloves when applying these products--even if it is not required by the label--because the spray will often get on whichever hand is holding the spray can.
Yellow jacket ground nest. Photo credit: Jim Baker, North Carolina State University, bugwood.org
Stinging insects can be scary but insecticides provide a very effective control against them. For paper wasps, after the spray dries you can knock down the remains of the nest.
When using any chemical product, here are a few things to keep in mind:
- Purchase the least toxic product first; choose a product with a "Caution" signal word.
- If treating a ground nest, make sure the product is labeled for ground nesting wasps.
- Do not spray in windy conditions or in a way that exposes yourself or others to the spray.
- Do not contact the spray when wet. Wait until the chemical has dried to knock down the nest.
- Keep these products from entering water, as instructed on the label.
- Most importantly, store these products carefully and out of reach of children. In Pennsylvania, exposures to pyrethrins and pyrethroids are the most common exposures reported to Poison Centers.
- Exposure to pyrethrins and pyrethroids is very rarely fatal, and most often induces skin and/or respiratory irritation.