The Right Trap for the Right Wasp
A common question I hear this time of year is, “My yard is overrun with wasps, and they are eating my raspberries and grapes. I put out a trap, but why hasn’t it helped?” The most likely reason is that the trap you are using is not attractive to the target wasp species. Since the invasion of the European paper wasp to Utah less than 10 years ago, this species has become a prominent nuisance and fruit-eating pest for growers and home gardeners. The primary type of wasp trap sold in garden and home centers contains heptyl butyrate, a chemical that is attractive to the yellow jacket wasp, but not to the European paper wasp.
Dr. Peter Landolt, USDA ARS Entomologist in Wapato, WA, studies the chemical ecology of insects, and has developed do-it-yourself traps to attract food-eating social wasps. The key is first determining the problem wasp species, and then selecting an appropriate trap.
The yellow jacket, shown at right, has a broad “waist” and more yellow than black color on its lower body (abdomen). It commonly builds its paper nests in the ground or under dense vegetation. Yellow jackets are primarily attracted to meat baits. A simple trap can be made by cutting the top from a plastic soda bottle and inverting it (without the lid) into the bottom “cup.” Punch a hole on each side of the cup and hang the trap using wire or twine. Hang a piece of meat, such as hamburger or fish, just below the funnel-shaped top and fill the cup with water plus 1 tsp. detergent. Position the meat so that the wasp will fall into the soapy water when it attempts to fly away after cutting off a piece.
The European paper wasp has a narrow waist and more black than yellow on its abdomen. This wasp builds upside-down umbrella-shaped paper nests and attaches them to overhangs, decks, and other structures. The European paper wasp is highly attracted to decaying fruit. Landolt recommends loading the soda bottle trap previously described with a mixture of 1 part fruit juice to 10 parts water + 1 tsp. liquid detergent. The juice must begin to ferment in order to be attractive, and so it may take a day or two for rapid fermentation to begin. You can accelerate the fermentation by adding a piece of overripe fruit.
If you need assistance with identifying a wasp, collect and submit a sample to the Utah Plant Pest Diagnostic Lab.