EB0643 Western Yellowjacket Paravespula pensylvanica YellowjacketsYellowjackets andand PaperPaper WaspsWasps Paper Wasp Polistes Yellowjackets and Paper Wasps Peter J. Landolt and Arthur L. Antonelli Yellowjackets and paper wasps as under bark, in stumps and become pestiferous. About this are beneficial insects. They feed logs, and within stacks of fire- time, new males and queens are their young numerous insects wood. The native Polistes aurifer produced from reproductive cells. that ordinarily damage shade (golden paper wasp) frequently These emerge and mate. The trees and crops. They also kill overwinters in attics of homes. males soon die, and the insemi- countless houseflies and blow nated queens seek sheltered loca- flies. The queens emerge during the tions in which to overwinter. The first warm days of spring (as abandoned nests rapidly decom- A few species of yellowjackets, early as March and April), select pose and disintegrate during the however, such as Vespula pensyl- a nest site, and build a small winter. They are not used again. vanica (western yellowjacket), paper nest in which they lay In spring, the cycle starts over. V. germanica (German wasp), their eggs. When the eggs hatch, and V. vulgaris (common yellow- the queen feeds the young larvae The German wasp has become jacket), scavenge for meat and for up to 3 weeks. Larvae then widespread in Washington. sweets and can become pests, pupate, to emerge as smaller The cycle of this yellowjacket is especially at picnics and camp- infertile females called workers. slightly later, with peak colony grounds. Even though they may Once the first five to seven work- size occurring in October and at times become pests, yellow- ers appear, they begin rearing early November. This species has jackets and paper wasps are and feeding the brood. The queen a propensity for nesting in struc- highly beneficial. Do not control rarely is seen again outside the tures and has become a wide- them unless their stings present nest. The colony then expands spread urban pest. Recently, the a hazard. rapidly, and depending on the European paper wasp (Polistes species, may consist of as many dominulus) also has become wide- Life Cycle as 5,000 workers and 15,000 spread and abundant through- In the Pacific Northwest, yellow- cells in the nest for some yellow- out Washington. It readily nests jackets and paper wasps have jacket species. on and within human-made annual colonies. The only colony structures and is particularly members to overwinter are insem- Colonies attain maximum size populous in urban and subur- inated queens, which spend the in August and September. Worker ban areas. The tendency of the winter in protected locations, such yellowjackets, then at their peak, German and European species to found nests in association with people contributes to their pest status. Identification A typical yellowjacket worker, Vespula pensylvanica, is shown on the cover. Yellowjacket work- ers are about 1/2 inch long, and appear short and stocky. All yellowjackets are yellow and black or white and black. Paper wasps are up to 3/4 inch long, and are more slender (see cover). Paper wasps may be distin- Paper wasp queen, Polistes aurifer (= fuscatus aurifer), tending guished from yellowjackets by aerial nest. their more slender body shape 2 LIFE CYCLE OF YELLOWJACKET. Diagram of underground nest sections, above left. Queen begins building a new nest in spring, upper right. Nest expands rapidly in summer as the number of workers increases, middle right. In late summer-early fall, worker populations and the colony are at their peak, lower right. The colony begins to decline, and the deserted nest disintegrates rapidly in winter. Queen, lower left, in diapause position, overwinters under loose tree bark, roof shakes, or other protected location. Worker populations reach their peak in late summer, center (not drawn to scale, workers are 1/3 to 1/2 the size of queens). New males and queens mate, lower right; males die, and inseminated queens seek winter shelter. The cycle begins again in spring. Maximum size is attained in August or September. 3 Nest of the aerial yellowjacket, Dolichovespula arenaria. Exposed subterranean nest of the western yellowjacket. Guard workers of the western yellowjacket on mud turret around entrance hole to subterranean nest. 4 and longer legs. Although the boxes, under eaves, chairs, and attic, it is advisable to remove it golden paper wasp is easily dis- benches, and within shrubbery. after the wasps are gone, because tinguished from yellowjackets the nest may serve as a home of by its yellow and dark brown Control carpet beetles or other insect pests. coloration, the newly introduced Yellowjackets and paper wasps European paper wasp is quite can be pests when they build Nests similar in color pattern to yellow- a nest on or near your house. Aerial nests. Aerial nests are jackets. Identification is impor- Yellowjackets may also be easily controlled using some of tant, because paper wasps are attracted in large numbers to the newer aerosol products that valuable as biological control food at picnics and to garbage propel the insecticide up to 20 agents of garden pests. cans. Various controls follow. feet. Effective materials to use Select those most suitable for are the synthetic pyrethroids, Types of Nests your needs. Remember, yellow- which have a quick knockdown Yellowjacket nests are built jackets and paper wasps are effect. Apply in the evening after entirely of wood fibers and con- beneficial insects—control them most yellowjackets or paper sist of multiple stacked combs only if only absolutely necessary. wasps have returned to the nest. completely enclosed by a paper Direct the initial spray stream envelope, except for a small Yellowjackets and paper wasps into the hole or face of the nest, entrance at the bottom of the do not reuse their nests the fol- then thoroughly wet the entire nest. Nests of most species are lowing year, although paper nest. Do not attempt to remove placed underground in rodent wasps may construct a new nest the nest until you are certain burrows or other soil cavities. adjacent to an old one. Knowing that all wasps are dead. This may The German wasp, however, this may help you decide if you take a day or two, since some often makes its nest inside walls want to risk being stung during foragers do not return to the of houses. The aerial yellow- a control operation, especially nest every night. However, when jacket (Dolichovespula arenaria) if the nest is in a rarely used area they do return, the insecticide and bald-faced hornet (Doli- of the yard. If you choose to leave residue should kill them rapidly. chovespula maculata) usually the wasps alone, the nest will make their nests in trees or on usually disintegrate over the Underground nests. Use a the outside eaves of buildings. winter months. If the nest is on registered hornet and wasp the eaves of the house or in an spray. Direct the material into Paper wasps also build nests of wood fiber, but their nests consist of a single comb not enclosed by an envelope. An average nest of the golden paper wasp, the only paper wasp native to Washing- ton, consists of about 200 cells, while the largest nest is probably less than 400 cells. Golden paper wasp nests are most noticeable under eaves of buildings, but they are also constructed in logs, under rocks, within shrubs and grass clumps, and inside pipe. Nests of the European paper wasp are often less than 100 cells in size but may possess 400 cells and more. This wasp appears to be quite flexible in selecting nest sites, including under roof Western yellowjacket workers often scavenge for meat or sweets shakes, within meter boxes, bird at picnics. Workers will feed pieces of meat to developing larvae houses, outside grills, and mail in the nest. 5 the entrance hole after dark. water with detergent added. The E The aerosol formulation listed yellowjackets will try to fly away to kill aerial nests will rapidly with pieces of fish or liver that F G kill subterranean colonies. After are too heavy for them, and will treating, do not plug the entrance fall into the water, where the 5” hole. Returning foragers will detergent acts as a wetting agent. enter the nest to be killed by Trapped yellowjackets, unable the insecticide residue. to fly, will drown. A cone trap can be baited with fresh or Nests in wall voids and canned meat. D attics. The aerosol formulations described under aerial nest con- Safety Precautions trol can also be used to kill nests Yellowjackets and paper wasps 7” in wall voids. Consider calling a may become aroused and attack commercial pest control opera- in defense of their nest when dis- C tor to treat nests in attics for turbed. If you decide to remove A safety reasons. Homeowners try- or spray a nest, follow these B ing to treat nests in close quar- precautions: ters like an attic are often badly • Cover yourself with thick stung or otherwise injured. clothing (including head, face, neck, and hands). Traps. A number of types of Cutaway view of cone trap: A. lures and traps are available or • Wear glasses to protect your plastic container with approxi- can be made to reduce numbers eyes. Some species are capable mate dimensions; B. entry holes of yellowjackets. Those commer- of squirting venom for short 5 distances and may target the on bottom—about /16-inch in cial lures that possess heptyl diameter; C. window screen cone butyrate are effective against face. with 5/16-inch hole at tip, set on the western yellowjacket. Other • Spray or remove aerial nests bottom of plastic container to chemical lures generally attrac- during the coolest part of the cover entry holes; D.