The District provides control for ground nesting yellowjackets when the location of the nest is known. There are a number of other insects that are sometimes confused with yellowjackets. The information below describes the differences between these insects and the reason the District does not control them.
What are yellowjackets?
Yellowjackets are stinging insects that build large communal hives. Three kinds of yellowjackets occur in San Mateo County: the Western Yellowjacket (Vespula pensylvanica), Common Yellowjacket (Vespula alascensis) and the Aerial Yellowjacket (Dolichovespula arenaria). The first two build hives under the ground and feed on live insects, dead animals, and nectar. These are the insects that pester you during your summer and fall BBQs. Aerial yellowjackets build large paper nests in trees or other high places (such as the eaves of your house). These nests are round or oval shaped and about the size of a basketball. Aerial yellowjackets feed exclusively on live insects.
Most of the time, yellowjackets are not aggressive and will not harm you if you stay out of their way. The yellowjackets that you see flying about in the garden are simply collecting food for their young and are helpful in controlling harmful insects in your garden. However, when their nest is disturbed, yellowjackets will swarm out and attack the offender. If you find a yellowjacket nest, be careful not to disturb it. If it is in a place you are likely to come into contact with, you can call the District to remove the nest.
What is the difference between yellowjackets and bees?
Yellowjackets feed on other insects as well as nectar, while bees feed only on nectar. Bees can only sting once while yellowjackets can sting multiple times. Yellowjackets have black and yellow stripes and shiny bodies while bees are fuzzy and brownish. Bees typically build hives in hollow trees high above the ground. Their hives contain wax combs. Yellowjackets build round paper nests either under the ground or hanging from tree branches. Bees produce honey and feed on nectar and pollen from flowers. They are important in pollination of fruit trees and many other crops.
Muddaubers
Muddaubers belong to the family Sphecidae. They have a very thin waist and long, dangly legs. These wasps are incredibly beautiful, some with smoky wings and a bright metallic blue body. There are more than 1,100 species in this family in North America. All are solitary with each female building an individual nest in which to lay her eggs. The nests are made out of mud, two to three inches across, with rows of round cells containing the developing embryos. The female wasp stocks each cell with a spider—food for the young wasps when they hatch. These beneficial insects are generally harmless and will help remove spiders from the exterior of your home.
Paper wasps
Paper wasps are similar to muddaubers. Females are solitary and build small nests from paper. These nests often appear along the eaves of homes during summer months. They are papery, two to four inches across, and have a honeycomb appearance when viewed from below. Like mud daubers, these insects are not very aggressive and do not defend their nests the way yellowjackets do. Because they hunt other insects and feed them to their young, these wasps are actually beneficial.
What kind of control services does the District provide for stinging insects like bees and wasps?
The District will control the nests of ground nesting yellowjackets, if the property owner knows the location of the nest. To find the nest, look for a hole in the ground, about the size of a quarter, with a steady stream of yellowjackets flying in and out. The District is not licensed to conduct pest control inside of structures. For nests inside of structures, please look in the yellow pages under “pest control” for a pest control expert with a structural license.
By applying the principles of integrated pest management, the District strives to minimize the use of pesticides and maximize their effectiveness when controlling yellowjackets. Control is aimed at removing the nest and destroying its ability to produce new generations of adults. These nests are controlled by applying an insecticidal dust to the nest opening. This material is carried inside by workers as they enter the nest. This kills the queen (the only colony member capable of producing eggs) and the developing larvae. Once the queen is gone, the workers will soon disperse and die. Broadcast sprays for the adult yellowjackets foraging about in the garden or around the barbeque are ineffective and dissipate quickly. They will have little or no impact on the yellowjackets in the area. Traps are also ineffective.
The District does not control honeybee nests because they do not usually constitute a hazard to public health. If you would like a nest or swarm of bees removed from your property, you can contact a professional beekeeper. Such companies can be found in the local yellow pages under “bee keeping services” or by contacting San Mateo Beekeepers’ Guild.
