Nuisance Wasps and Bees Fact Sheet No. 5.525 Insect Series|Home and Garden by W.S. Cranshaw* Wasps and bees can be a serious nuisance Quick Facts problem throughout Colorado, particularly late in the summer when certain yellowjacket • Most wasps develop by wasps forage at garbage and outdoor food feeding on insects. Bees areas. In overall balance, however, these develop on a diet of nectar or insects are beneficial in their activities, pollen. particularly as predators of pest insects and as pollinators. It is important to distinguish • Almost all insect stings result between the various wasps and bees because from yellowjackets and an their potential as problems and their insect newly established in control differ. the state, the European paper Figure 1: Yellowjacket entering nest wasp. underneath wall. Social Wasps • Yellowjackets, hornets and Several wasps are social insects that paper wasps make nests produce a colony. Colonies begin anew each of paper. Honey bees and spring, initiated by a single fertilized female bumblebees make nests of (queen) that has survived winter. The social wax. Solitary bees and wasps wasps construct their nest of paper, which nest in holes in the ground, they produce by chewing on wood, scraps of rotten wood or natural paper and cardboard. cavities. Some wasps even Social wasp colonies are very small early make mud nests. in the season, but expand rapidly through the summer as more wasps are raised that assist in colony development. By the end of summer, a colony may include dozens, or even several hundred, individuals. Some Figure 2: Baldfaced hornet. wasps reared at the end of the season are fertile females (potential queens) and a nectar, however, social wasps are generally few males. In fall, colonies are abandoned, not important plant pollinators. never to be reused, and the fertilized females All social wasps are capable of producing scatter to find protection during winter. The a painful sting but none leave the stinger remaining members of the colony perish with embedded, as do honey bee workers. cold weather. Most stings occur when the colony is Most social wasps rear their young on accidentally disturbed. a diet of live insects. Several types of social Yellowjackets (Vespula spp.) are wasps are important in controlling insect banded yellow or orange and black and pests such as caterpillars. An exception are commonly mistaken for honey bees, to this is the western yellowjacket, which but they lack the hairy body and are more primarily scavenges dead insects, earthworms intensely colored. Yellowjackets typically and other carrion, including garbage. This nest underground using existing hollows. scavenging habit is usually why yellowjackets Occasionally nests can be found in dark, © Colorado State University become serious nuisance problems. Male enclosed areas of a building, such as crawl Extension. 4/96. Revised 12/12. wasps occasionally visit flowers to feed on spaces or wall voids. www.ext.colostate.edu Nests are enclosed in a paper envelope, *Colorado State University Extension entomologist but they are not exposed nor observed and professor, bioagricultural sciences and pest unless excavated. The nest entrance is small management. 12/2012 and inconspicuous. Colonies are readily fall. The nest can be safely removed in the defended and yellowjackets will sting when winter or, if left alone, will break up during the nest area is disturbed. late fall and winter. Thewestern yellowjacket (V. Reducing paper wasps nesting sites pensylvanica) is, by far, the most important is possible before the colonies become stinging insect in Colorado. Late in the established in early spring. This is done season, when colonies may include up by sealing all openings that allow access to 200 individuals, they become serious to hollow tubing or similar materials. nuisance pests around outdoor sources of The interior of many kinds of children’s food or garbage. The western yellowjacket playground equipment are suitable nesting is estimated to cause at least 90 percent of sites by this wasp and should be given Figure 3: Western yellowjacket. the “bee stings” in the state. special attention. Hornets (Dolicho vespula spp.) produce Active nests causing problems can be large, conspicuous grayish paper nests in destroyed with an insecticide. Insecticide trees, shrubs and under building eaves. The applications are best made during late most common species is the baldfaced evening or cool periods in early morning, hornet (D. maculata) which is stout- when the wasps do not readily fly and most bodied and marked with dark and white foragers have returned to the colony. A striping. Hornets feed their young live variety of insecticides are currently sold insects and do not share the scavenging for this purpose with active ingredients habit of yellowjackets. Nests often attract including permethrin, deltamethrin, attention because of their large size, but tralomethrin, bifenthrin, tetramethrin, hornets rarely sting unless the colony is allethrin, and esfenvalerate. Many of these seriously disturbed. are combination products that include a Figure 4: Baldfaced hornet nest cutaway to Paper wasps (Polistes spp. and the fast-acting, short-lived ingredient (e.g., expose paper comb. western paper wasp, Mischocyttarus allethrin, tetramethrin) with an insecticide flavitarsus) make paper, open cell nests that is more persistent in ability to control that are not covered by a papery envelope. wasps (e.g., permethrin). Often these nests are produced under For exposed nesting species, such as building overhangs. However, a new species paper wasps, insecticides can easily be to Colorado, the European paper wasp applied directly to the nest and control (Polistes dominula), will also nest in small should be excellent. However, ground cavities in the sides of buildings, within nesting yellowjackets with only a small metal gutters and poles, outdoor grills, external entrance can be much more and similar items. Paper wasps are more difficult to control since the nest may slender-bodied than other social wasps. actually be some distance from the Most native paper wasps are reddish-brown opening. Repeated insecticide applications and marked with yellow, but the European are often required to destroy existing paper wasp is marked with shiny black and yellowjacket nests. Figure 5: The western paper wasp, a native yellow, allowing it to be easily mistaken for Social wasps nests are more easily species of paper wasp. a yellowjacket. controlled early in the season when Paper wasps are beneficial predators colonies are small. of caterpillars and other insects and do Nuisance problems with scavenging not scavenge. However, the habit of the yellowjackets are difficult to manage unless European paper wasp to nest in many all the nests are found and destroyed. locations around a yard has greatly However, nests are inconspicuously located increased the incidence of stings associated and the wasps may fly as far as 1,000 yards with this group of wasps. from the colony while foraging, so complete control is difficult. Control of Social Wasps Many concerns with social wasps occur Commonly sold wasp traps only late in the season when colonies grow large are effective for yellowjackets. They and the above-ground nests of hornets and are not attractive for paper wasps or paper wasps become apparent. If the wasps hornets and will not assist in control of are not causing a problem, the best solution these types of wasps. Figure 6: European paper wasp. is to wait until the nest is abandoned in the Table 1. Physical description of the most common bees and wasps. Honey bee (Apis mellifera): Very hairy. General color orange or yellow-orange, sometimes with dark gray. Individuals collecting pollen will pack it into clumps in special structures (pollen baskets) on the hind legs. Bumble bees (Bombus spp.): Very hairy and stout bodied. Black and yellow markings on all species but many are marked with orange or orange-red on the abdomen. European paper wasp (Polistes dominulus): Not hairy. General color black and bright yellow. Overall body form more elongate than the other species. Hind pair of legs long and trail conspicuously when flying. Western yellowjacket (Vespula pensylvanica): Not hairy. General color black and bright yellow. Overall body form slightly more compact than European paper wasp. Baldfaced hornet (Dolichovespula maculata): Not hairy. General color is black and creamy white. Overall body form similar to yellowjacket, but larger. Figure 7: Yellowjacket traps. Yellowjackets will regularly return of spider wasps, the sting is quite mild to sites where food and water sources compared to that of social wasps. are available. Therefore, it is important An unusual wasp common in prairie to deter yellowjackets from visiting an areas are the velvet ants. Females are area by eliminating all food sources (e.g., wingless, hairy, extremely active and open garbage cans, pet foods). Water possess a painful sting. Velvet ants develop sources around the yard may also attract as parasites on ground-nesting bees. yellowjackets during hot, drought- Another important group of wasps are stricken periods. the parasitic wasps. These wasps lay their There has been some success using baits eggs in other insects and the developing Figure 8: Mud dauber. and traps for control of yellowjackets. The wasp larva slowly consumes and ultimately (Photo from the K. Gray collection.) western yellowjacket is attracted to the kills the host insects. Parasitic wasps are chemical heptyl butyrate, which is included non-aggressive, only sting when handled, as a lure in many wasp traps. Such traps can and are considered beneficial for their be helpful when used early in the season, role in controlling a wide variety of pest June and early July, when the number of insects. They are discussed further in fact yellowjackets is small and the colonies are sheet 5.550, Beneficial Insects and other struggling to become established. However, Arthropods. these traps will not attract European paper wasp and are worthless for control of this species.