The Free Press, Mankato, MN

September 18, 2013

Time to look out for yellowjackets

Jeffrey Hahn
U of MN Extension Entomologist

---- — This is the time of year when yellowjacket nests are reaching their maximum size and become conspicuous to residents.

Two sites where yellowjackets are most problematic are nests that are in the ground and those that are in hidden voids in buildings. A lot of people have mistakenly identified yellowjackets as bees (perhaps because of all of the recent discussion of bees in the media) and are looking for information on how a yellowjacket nest can be moved and saved. Yellowjackets are not important pollinators and it is not necessary to take extraordinary measures to save them. There are not any services that will remove a yellowjacket nest and relocate it.

Yellowjackets are about a half-inch long, black and yellow, and with few hairs on their body. While honey bees are a similar size, they are mostly a golden brown with black stripes on their abdomen and hairy. While yellowjackets are very common around structures, honey bees are rarely found around homes. Correct identification of stinging insects is further complicated as many people use the term "bees" for yellowjackets and wasps bees. Be sure your insects are correctly identified so you know the correct course of action to take (if a nest found around a home isactually turns out to be a honey bee colony, contact the Minnesota Hobby Beekeepers Association for help in removing them).

When yellowjackets are found nesting in the ground, they are challenging to control as you do not actually see the nest, just the burrow entrance that will lead to it. It is tempting to use an aerosol wasp killer; however, the insecticide does not get into the nest and has minimal effect on the yellowjackets flying back and forth.

The most effective means of controlling a subterranean nest is with a dust labeled for ground-dwelling insects, although there is generally not any product like this available to the public.

Another option is to use a liquid insecticide, pouring it into the nest entrance, but this is less effective. If you do attempt control, apply it at the entrance of the nest at night when yellowjackets are less active. Check after a day to see how effective the treatment was and repeat if necessary. If you are not successful yourself, then consider hiring a pest management service to treat the yellowjackets for you.

Yellowjacket nests that are found inside homes in wall voids, attics, concrete blocks, or similar spaces are equally or even more challenging. You cannot see the nest, similar to a subterranean nest, but you can see the workers flying in and out of an opening or crack. A dust labeled for use in homes would ideally be the most effective method but these products are generally not available to the general public.

Treatment tips for yellowjackets If you decide to treat a yellowjacket nest found out in the open, here are some treatment tips: • Choose one of the widely available wasp or hornet spray products with active ingredients such as resmethrin, tetramethrin, permethrin, or prallethrin. • Wait until evening to spray the nest. Yellowjackets are not very active when it is dark. • Spray the insecticide directly into the nest entrance, located on the bottom. • Check it the next day. • If there is still some activity, treat again.