What's the Buzz?
Many people confuse honeybees with Yellowjackets. If you’re close enough, examine the abdomen (I heard that“ICK!!”): the honey bee has a stocky, hairy body; Yellowjackets have a slender, hairless body. Yellowjackets are also more brightly colored than honeybees. These wasps become more active and aggressive as the days shorten and the nights cool. (Perhaps they know their days are numbered!?) When you call the office worried about aggressive bees in your yard, I assume you mean Yellowjackets, especially at this time of the year.
Yellowjackets can be found nesting in a variety of different places. Aerial nests can be found hanging from tree limbs or the eaves of homes. Subterranean nests can often be found in old mouse burrows, and existing holes in the ground. They can also nest in buildings, attics spaces and behind interior walls. The nests are present all season, but may not be noticed until late summer when the workers are more numerous.
Aerial nests are relatively easy to manage. If they pose no problem, leave them until winter, and then remove them. If they are a hazard, wait until evening, when the wasps are less active, and spray the nest with a long range wasp and hornet spray. Check the next day to see how effective this treatment was. If you see wasps flying around, you will need to re-treat.
Subterranean nests are much more difficult to manage. The entrance to the nest is quite small, and the nest can be recessed several feet from the entrance. This makes high powered sprays ineffective. The most effective way to control a subterranean nest is with a dust labeled for ground dwelling insects. 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.
Nests within the walls of buildings are the most difficult to deal with. Finding the exact location of the nest is challenging, and simply spraying the entrance with an indoor insecticide can drive the wasps further within the walls. The most effective chemical controls are not readily available to homeowners. The best method to control hidden nests in buildings is to have a professional pest control company treat the nest.
The good news: yellowjackets die when the weather gets below freezing. If you are dealing with a nest late in the season, it might be easiest to wait until the cold temperatures kill them. Nests are also not reused the following spring.
For more information about wasps and bees, check out the Extension Website at www.extension.umn.edu.