Managing Yellow Jackets
in the Puget Sound Region
Evan A. Sugden, Ph.D.
Usefulness of Wasps. Yellow jackets are predators and consume ten times their weight in other insects, mostly grubs and caterpillars in your garden. Therefore, they have great value as biological control agents and may be helping you. Consider this before further action.
Types of Wasps. There are two major types of wasps in this category. True ³yellow jackets² are about the size of a honey bee and live in paper-ball like nests that may have hundreds or thousands of individuals. There are several species; some are more defensive and bothersome than others. Nests of yellow jackets can be found aerially, in trees or under eaves, or they can be found in the ground where they are typically made in the abandoned dens of rodents. The other type of wasps is ³paper wasps². These are slightly larger, are more slender, and have longer legs. Their nests are smaller and consist of an ³inverted umbrella² shape with a single layer of comb, or cells, in which the larvae are reared. There are several species. Paper wasps are generally not as defensive as yellow jackets.
Wasp Biology. Both yellow jackets and paper wasps typically have annual colonies. This means all the wasps will eventually leave the nest by late summer or autumn and the nest will die out on its own. As summer progresses, the wasps¹ food sources (other insects) decline, and they begin to starve. Also, they become desperate for food and begin to forage on garbage and a wide range of protein. This is when they become a serious nuisance. An exception is one exotic species in the Puget Sound area that can over winter. In this case, the nest may continue to grow over several years, attaining a gigantic size, even partial filling a closet or small room.
Problem Wasps. Sometimes you cannot tolerate wasps in your yard. If you know where the nest is, you may be able to take simple direct action. THIS IS NOT A RECOMMENDATION but a relation of my personal experience as an entomologist, beekeeper, and wasp research scientist. DO NOT ATTEMPT TO EXTERMINATE WASPS without forethought, protection, and supervision.
HOW I GET RID OF AERIAL NESTS. Spraying often does not help. In the case of yellow jacket nests, most of the insects are inside and will not be contacted by the spray. They will be flying tomorrow! The effects of the spray on other organisms, especially pollinators, may be worse than the mild threat posed by the wasps. I always prefer direct physical removal. The wasps will all be in the nest at night. In a protective suit I carefully approach the nest with a double-thick plastic garbage bag. I quickly clasp the bag around the nest, pull it off its attachment point, and then seal the bag. Sometimes I have to clip off a few branches from the tree to reach the nest. Once in the bag, the nest can be frozen, burned, or buried. If it is small enough to freeze I later remove the larval combs and feed them to my chickens. If I feel I have to spray I use the LEAST BEE-TOXIC spray available and use only according to instructions. Once I remove a wasp nest from a ceiling space or a wall I carefully seal up the point at which the wasps entered so another colony will not form there next year.
HOW I GET RID OF GROUND NESTS. Appropriately protected, I approach the nest at night once I have located the entrance hole. The wasps are easily subject to drowning, so I flood the nest hole with a garden hose. Just to make sure I put a board over the entrance. In time the nest cavity may collapse and the ground will sink a little.
OTHER LINKS TO WASP INFORMATION:
Washington State University (PDF)
same as above but HTML
University of Minnesota