Controlling Wasps In The Yard

Yellowjackets and other social wasps may be found in large numbers as we enter late summer and through the fall. Most of the wasps are beneficial and feed on garden pests, however, some can become aggressive. Most stings will come from the Western yellowjacket species of wasp. To begin controlling the wasps in your yard, it is important to first properly identify which species is present.

The most common wasps in Montana are bald-faced hornets, paper wasps, and Western and aerial yellowjackets. Paper wasps are yellow and black. Yellowjackets are also mostly yellow and black, whereas bald-faced hornets are mostly all black with just a bit of white.

Traps are available for western yellowjackets; however, they are most effective when they are placed out in early spring. At this time in late summer, controlling some of the larger nests may be more difficult as there may be thousands of wasps within a nest that can be the size of a basketball or larger. Western yellowjacket nests may be hard to find and are usually on the ground, whereas bald-face hornet nests are usually up in a tree. If a nest is exposed and accessible, soapy water can be applied to it. Exposed and accessible nests can also be enclosed with a large garbage bag at night and then frozen, being sure to wear protective clothing. There are chemical sprays available for actives nests. Use products with active ingredients such as deltamethrin, tralomethrin, permethrin, bifenthrin, tetramethrin, and allethrin. Apply these products late in the evening, early in the morning, or on a cool, rainy day when the nests are not as active. Removing food sources such as garbage cans or drippings from the grill from around your home will also help, as the wasps are attracted to these. After the weather turns cool and there are a few frosts, you can knock down the nests, as these abandoned nests are not used the next year and will decompose during the winter.

If you have any questions, contact the MSU Richland County Extension Office at 406-433-1206 or [email protected].