There are several species of yellowjackets across North America. Most have a distinctive pattern on their abdomen that tells them apart from the others. While most yellowjackets are yellow and black, some are white and black. Yellowjackets belong to a subfamily that contains Vespula and Dolichovespula species. Vespula species tend to nest in the ground or in above-ground voids and Dolichovespula species tend to build aerial nests. Although the baldfaced hornet was given the name “hornet” because of its large size, it is a Dolichovespula species of yellowjacket.
Yellowjacket nests contain multiple comb layers enclosed by a paper envelope with one entry and exit hole. Colonies are usually annual and die in the fall, with only newly mated queens overwintering in sheltered locations. Large perennial nests may occur where winters are mild. Yellowjackets become dangerous pests when they nest in, on or near man-made structures because they become aggressively defensive when disturbed. A group of Vespula species will sting away from their nests because they tend to scavenge for food instead of hunt for live prey. This often happens in recreational areas and around garbage cans.
When a nest is found, an aerosol or dust formulation can be applied to the nest opening. These formulations travel through the nest well. If necessary, they can be applied to the sides of the nest by poking through the paper envelope. Nests can also be drenched with a liquid residual. In general, repellent formulations that kill quickly can also excite the colony into defensive aggression. Colonies may be less reactive to non-repellent formulations, but they take a little longer to kill the colony.