Yellowjackets, Bald-Faced Hornets, and Paper Wasps “

HOMEOWNER Guide to by Edward Bechinski, Frank Merickel, Lyndsie Stoltman, and Hugh Homan BUL 852 Yellowjackets, Bald-Faced Hornets, and Paper Wasps “ . . . spring weather largely determines if we will have wasp problems or not in any given year. Cold, rainy weather during April and May reduces the likelihood”

TABLE OF CONTENTS I. IDENTIFICATION ...... 3 - 7 Yellowjackets ...... 4 Western ...... 4 Common ...... 4 German ...... 5 Aerial ...... 5 Bald-faced hornets ...... 6 Paper wasps ...... 6 II. SEASONAL LIFE CYCLE ...... 7 Box: Saving Nests ...... 7 III. STING HAZARDS Localized, toxic and allergic reactions ...... 8 Box: Advice for encounters ...... 9 IV. MANAGEMENT STRATEGIES ...... 9 Personal protection ...... 10 Repellants ...... 10 Reduce access to food and water ...... 10 Nest destruction ...... 10 Traps ...... 11 Biological control ...... 12 Box: Poison bait ...... 12 Table 1 Commercial traps, attractants ...... 13 Insecticides How to select the right product ...... 13 Box: Safety precautions before you spray ...... 14

2 HOMEOWNER Guide to YELLOWJACKETS—WASPS IN THE VESPULA OR DOLICHOVESPULA GENERA—UNLIKE BEES—ARE SHINY AND BARE OF HAIR. THEY’RE ALSO SLEEKER THAN BEES. OF 11 SPECIES FOUND IN IDAHO, THESE FOUR ARE THE MOST COMMON. ALL CAN STING MULTIPLE TIMES.

WESTERN YELLOWJACKET, Vespula pensyl- COMMON YELLOWJACKET, Vespula vulgaris, vanica, Idaho’s most abundant species, builds also builds underground nests around the underground nests in abandoned animal bur- yard. It feeds on insects but scavenges from rows, hollows under sidewalks, and crevices in picnics as insect prey becomes scarce. retaining walls. Papery nests: Underground. Papery nests: Underground. Picnic pest: Yes. Picnic pest: Yes. Photo © Neil Miller/Papilio/Corbis Photo from www.worsleyschool.net

GERMAN YELLOWJACKET, Vespula AERIAL YELLOWJACKET, Dolichovespula germanica, an aggressive scavenger of meats arenaria, mostly builds nests above ground and sweet drinks, poses high sting hazard. It that can grow to impressive sizes. Papery may survive Idaho winters when nesting in wall nests: Builds nests both underground and voids and home attics. Papery nests: In home above ground on roof overhangs or on wall voids and in attics. Picnic pest: Yes. protected building surfaces. Picnic pest: Photo © Andy Wehrle/bugguide.net Not usually. Photo © Craig Persel

BALD-FACED HORNETS, Dolichovespula PAPER WASPS, Polistes, in color are similar maculata, are heavy-bodied, black-colored to yellowjackets, but they have a slimmer, wasps with pale yellow-white marks on the elongated body shape and a long-legged head and at the end of the abdomen. Papery appearance. Legs hang down even during nests: Often high in trees or at roof peaks; flight. Papery nests: Resemble an open soccer-ball-sized nest is not unusual by fall. umbrella with individual comb cells open Picnic pest: Little risk. They’re not aggressive. to view from below. Picnic pest: No. Photo © Dennis Schotzko, University of Idaho Photo © Dennis Schotzko, University of Idaho

Yellowjackets, Bald-Faced Hornets, and Paper Wasps 3 YELLOWJACKETS AND THEIR RELATIVES have well-earned reputations for painful stings. Yet when these insects occur at safe distances from human activity, none automatically requires elimination from yards and gardens. All instead should be considered beneficial pollinators, predators, or scavengers. This publication will help you understand differences in the biology and sting threat posed by the most important types of yellowjackets, hornets, and wasps encountered around Idaho homes. Information here will help you decide first if control action is needed. Then it will help you determine your best options.

they cooperatively rear and vigorously Species identification requires expert defend their immatures. examination but is not necessary to decide if control action is needed. TRIO OF PAPERY NEST BUILDERS Yellowjackets, bald-faced hornets, and The western yellowjacket is our paper wasps all build grey-to-tan most abundant species. It shares papery nests of fibers chewed from many biological features with another weathered wood. Adult wasps often frequently encountered species, the can be seen around yards, gnawing common yellowjacket. Both are pulp from backyard fences, firewood, native to Idaho. Their natural habitat and even cardboard stacked outside is dry grass and wooded areas, but for recycling. Nests consist of they readily nest around home Photo © Terry Thormin/Royal Alberta Museum hexagonal-shaped cells arranged landscapes. side-by-side into horizontal layers IDENTIFICATION These two yellowjackets almost of comb. Nest shape, size, and always build subterranean nests The words bee, wasp, yellowjacket, placement distinctly differ among hidden from view within natural and hornet often are used these three major insect groups. cavities (Figures 2, 3a, 3b). Typical interchangeably—but incorrectly—to These differences are explained in backyard nest sites include describe any medium-to-large, yellow- the following sections. abandoned animal burrows, hollows and-black stinging insect. Bee is a YELLOWJACKETS—4 SPECIES under sidewalks, and crevices in broad term that describes a diverse POSE STING HAZARDS NEAR landscape retaining walls. In forested group of insects whose body is at least IDAHO HOMES areas, these two yellowjackets build partly covered in fine hairs. Wasps Yellowjackets are medium size nests within fallen logs, old stumps, differ physically from bees in that their (about 1/2-inch long) black wasps and in the soil. bodies are almost bare and shiny. marked with irregular, jagged yellow YELLOWJACKETS EAT INSECTS, Yellowjacket technically only refers bands. They become pests at picnics MEAT, SWEET NECTAR to wasps in the scientific genera and other outdoor settings where Unlike honey bees, yellowjackets do Vespula or Dolichovespula. Names are meats and sugary drinks are present not produce honey, nor do they store even more confusing because hornet (Figure 1). floral nectar in nest cells. The is used informally in the United States Eleven different species of western yellowjacket and the to describe certain large species of yellowjackets are known in Idaho, common yellowjacket primarily Dolichovespula yellowjackets that but normally only four species pose feed as predators on living insects, build aerial nests. Biologically sting hazards that sometimes justify especially during the spring and speaking, the only true hornets are control action: (See photos on p. 3.) early summer. Workers search members of a still different genus, out caterpillars, beetle grubs, Vespa, none of which occurs in Idaho • western yellowjacket grasshoppers, flies, spiders, and or any adjoining western state. Vespula pensylvanica other soft-bodied prey, which they Yellowjackets and their commonly • common yellowjacket return to the nest as chewed-up encountered relatives—the bald-faced Vespula vulgaris food for their own developing larvae. hornet and paper wasps—are Yellowjacket workers kill prey by • German yellowjacket social wasps. They live as a single biting, not stinging. Adult Vespula germanica reproductive female (the queen) and yellowjackets themselves ingest her infertile female offspring (the • aerial yellowjacket some body liquids from prey but workers) in a central nest where Dolichovespula arenaria mainly feed on plant nectar. Workers

4 HOMEOWNER Guide to Figure 1. Yellowjacket workers also feed mouth-to-mouth on liquids produced by scavenge food from meat their larvae. As summer progresses and insect scraps. Photo © Whitney Cranshaw, Colorado State prey becomes scarce, western and common University, yellowjackets increasingly feed as scavengers on www.insectimages.org non-living proteinaceous (protein) and sugary foods. Workers naturally feed on carrion, nectar, and honeydew (the sugary liquid secreted by aphids and scale insects). Landscape trees with yellowjackets flying about during late July and August usually indicate the trees are infested with honey- Figure 2. Yellowjacket workers dew-producing aphids or scale insects. hover near opening to nest located in hidden cavity behind Scavenging feeding behavior increases human brick wall. Photo © Whitney sting hazard because it places yellowjackets in Cranshaw, Colorado State close contact with people. University, www.insectimages.org Meats and carbohydrate drinks at picnics or inside garbage cans attract large numbers of yellowjackets that readily sting. Overripe fruit that fall from backyard fruit trees also attract large numbers of foraging workers. GERMAN YELLOWJACKET IN IDAHO SINCE 1980S The German yellowjacket is a European species first recorded in the northeast U.S. during the 1970s and subsequently in Idaho during the 1980s. entry It poses a high sting hazard to people because it is l another aggressive scavenger of meats and sweets (as well as a voracious predator of living insects). The sting hazards posed by the common, the comb tiers western, and the German yellowjackets have with cells l Figure 3a. Cross-section of a closed school playgrounds and resorts, curtailed typical subterranean yellowjack- logging operations, and interfered with et nest hanging within an commercial fruit harvest. underground cavity shows tiers of horizontal comb where imma- The German yellowjacket can be a special ture life-stages are reared by workers. Worker yellowjackets pest problem because it sometimes builds crawl down soil cavity and enter nests in wall voids and attics of homes. Other nest through an opening at the yellowjackets naturally die out with cool fall bottom of the outer wall. Figure temperatures, but the nesting habits of German from Akre et al. 1980 USDA l Agriculture Handbook 552 yellowjackets potentially allow colonies to persist

outer year-round in the mildest areas of Idaho. nest wall l AERIAL YELLOWJACKET MAKES nest opening ABOVE-GROUND NESTS The other frequently encountered species is the aerial yellowjacket. It mostly builds nests above entry l Figure 3b. Compare diagram- matic illustration 3a with actual ground, although below-ground nests are not yellowjacket nest exposed by unusual. The above-ground nests are similar in digging away surrounding soil. form to subterranean nests of the common, In late season, one nest can house thousands of workers. western, and German yellowjackets. Nests consist outer nest wall l Photo from Ken Gray slide of layers of papery comb wrapped by an outer collection, Oregon State envelope with an entry hole. Nests occur from University ground-level to tree-top heights on all types of nest opening l vegetation. Aerial yellowjackets also commonly build nests from roof overhangs or other protected exterior surfaces of buildings. Nests grow to impressive

Yellowjackets, Bald-Faced Hornets, and Paper Wasps 5 sizes as summer progresses and may contain as many as 700 workers. Aerial yellowjackets normally prey on living insects and so are not nuisance pests around picnic foods or garbage cans like the other three. An exception occurs in late summer when aerial yellowjackets are attracted to sugary foods. Control of aerial yellowjackets is warranted only if people or pets routinely pass near nests or people with known allergies to wasp venoms are present. BALD-FACED HORNETS BUILD LARGE AERIAL NESTS The bald-faced hornet, Dolichovespula maculata, is a large (3/4-inch), stout- bodied, black wasp with a whitish-yellow face and a few whitish marks near the end of the body (see p. 3). Like the aerial yellowjacket, bald- faced hornets build enclosed, papery Figure 4. Bald-faced hornet nest is similar in form to subterranean yellowjacket nests but above-ground nests on landscape always is located above ground, usually on landscape plants or buildings. They can get as plants and buildings (Figure 4). large as soccer balls by early fall. Note two nest openings through the outer wall on the left side, bottom third. Photo by University of Idaho Bald-faced hornet nests often have leaves and twigs in the outer nest wall, whereas nests of aerial yellowjackets do not. during 1999. The European paper Reduced sting hazard. In spite of wasp now occurs statewide in Idaho their large size, bald-faced hornets and ranks as our most commonly pose a substantially reduced sting encountered stinging pest. hazard compared to yellowjackets. Umbrella-shaped, open nests Bald-faced hornets almost entirely Paper wasps build distinctive feed on other living insects, including umbrella-shaped paper nests yellowjackets, and so do not become (Figure 5) seen hanging upside-down nuisances at outdoor events where from doorframes, eaves, and other food is served. Potential for stinging protected places. Nests are open- encounters also is reduced because combed, meaning cells are not nests of bald-faced hornets often are Figure 5. Paper wasps build nests that enclosed by an outer envelope like located high in trees or at roof peaks. resemble an open umbrella with individual nests of yellowjackets and bald-faced Workers will sting when provoked (by comb cells open to view from below. Photo hornets. Individual cells can be seen someone bumping the nest or from Ken Gray slide collection, Oregon State University when viewed from below (looking squeezing hornets against the skin), up into the nest). Like yellowjackets but are not as aggressive in defending and hornets, paper wasps are social nests as yellowjackets. the most common type of paper wasp insects. PAPER WASPS—IDAHO’S MOST throughout the Gem state until the Paper wasps are beneficial predators. COMMON STINGING PESTS late 1990s. Although this native They do not scavenge on non-living Paper wasps resemble yellowjackets species still occurs in rural areas of foods as do nuisance yellowjackets but have a slimmer, elongate body Idaho, it largely has been displaced but instead prey on caterpillars and shape with a characteristic long-legged in urban habitats by Polistes dom- other soft-bodied, leaf-feeding appearance (see p. 3). Their legs even inulus, the European paper wasp. insects. Adult paper wasps also feed dangle below the body in flight. The non-native European paper wasp on nectar, so can be seen foraging on The golden paper wasp, Polistes was first observed in Massachusetts flowers. During summer you’ll often fuscatus aurifer, a yellow-to-reddish- during 1981. It expanded westward find them around your yard’s water brown wasp with yellow banding, was reaching the Pacific Northwest puddles and ponds.

6 HOMEOWNER Guide to ! • Inside outdoor light fixtures, winters as solitary but mated females SAVING YELLOWJACKET AND mailboxes, cable TV/home-utility called queens. None of these species BALD-FACED HORNET NESTS boxes, exterior door chimes, overwinters within their nests. These The large papery nests that covered barbeque grills, bird reproductive female wasps instead aerial yellowjackets and houses, and bird feeders overwinter outdoors under loose tree bald-faced hornets build in bark or on the ground in weedy areas • Fenders, bumpers, and other landscape trees and shrubs that provide cover. exterior surfaces of vehicles can be brought into homes parked for long-term storage An exception to outdoors safely during late fall as indoor overwintering is the golden paper decorations or curiosities. • Exterior walls of homes— wasp, which sometimes overwinters especially those covered by ivy On cool November days, in home attics or other unheated or other creeping vines clip abandoned nests from parts of buildings. They can become branches, then bag and place • Limbs and foliage of landscape stinging pests inside homes during in the freezer one or two days. shrubs, particularly dense late winter when sunny days raise Freezing kills any remaining evergreen shrubs temperatures in attic spaces, and workers or other insects—like wasps escape into household living • Under stone ledges in rock gardens earwigs—that sometimes live in quarters. Wasps flying around and within crevices between old nests. Physically shake any windows inside Idaho homes during landscape timbers dead insects and other debris winter usually are Polistes paper from the nest; otherwise, nests • In home attics, wall voids, and wasps. can become an odor problem. similar spaces where vents or holes SPRING—NESTBUILDING; allow wasp entry You could wait until the hard WEATHER DETERMINES freezing days of winter to • Under eaves, shutters, patio decks, WASP PROBLEMS collect the nest, but papery and similar overhanging places Overwintering queens emerge from nests are delicate and hibernation during the first warm • Inside folded outdoor umbrellas, disintegrate quickly under days of spring in March and April. under seats and armrests of patio harsh winter weather. They immediately begin to feed on chairs, and under tables nectar and readily can be observed • Within hollow-framed outdoor around home landscapes on furniture or hollow fencing flowering plants or at water sources. Fairly docile. Compared with • On roofs under cedar-shake shingles Yellowjackets, bald-faced hornets, yellowjackets, European paper and paper wasps build new nests wasps are relatively docile. They Other paper wasps only build nests each spring. None re-uses nests from don’t aggressively attack people, but that hang horizontally from year to year. Yellowjackets and bald- will sting to defend their nest when protected places, but the European faced hornets work as individual provoked. People are stung when paper wasp also builds nests queens to construct their own nest. they accidentally contact a hidden attached vertically to protected European paper wasps sometimes nest, such as inadvertently touching surfaces. This nesting behavior, work together as cooperating a nest with a bare hand while together with their high relative overwintering queens to make a gardening. abundance, places European paper single shared nest. wasps in routine contact with European paper wasp nests— people. In all of these species, the queen lays almost anywhere a single egg in each cell. Eggs hatch European paper wasps are pests but European paper wasp nests often are into small, legless, whitish grubs, not because they aggressively sting. golf-ball size and consist of 20 or each occupying one cell in the comb Unless you accidentally physically fewer cells. Nests with hundreds of (Figure 6). The queen cares for her contact the nest itself, wasps often cells are possible in the warmer parts larvae by feeding them chewed-up respond to disturbance by flying of Idaho where hot, dry weather insects that she captures from about the nest rather than stinging. allows for prolonged reproduction. backyard plants. However, European paper wasps have become statewide sting threats SEASONAL LIFE CYCLE Grubs develop through several because they readily build nests in successively bigger stages, eventually just about any protected backyard transforming into pupae and WINTER—MATED QUEENS site and so frequently are emerging as adult worker wasps SURVIVE OUTDOORS encountered by people. Common about one month after eggs are laid. Yellowjackets, bald-faced hornets, nests sites around the home include: Workers are entirely comprised of and paper wasps survive Idaho

Yellowjackets, Bald-Faced Hornets, and Paper Wasps 7 Paper wasp nests in Idaho are become scarce and workers substantially smaller, seldom aggressively scavenge picnic food exceeding 100 individuals and often scraps; they also more vigorously comprising fewer than 20 individuals. defend their nest as new reproductive queens and males are FALL—NEW QUEENS DEVELOP; produced. SUMMER COLONIES DIE In early fall, workers build special Multiple stings. Stings of nest cells where new reproductive yellowjackets, hornets, and paper males and queens are produced. wasps are smooth, sharp needles When new queens and males emerge that repeatedly can be pushed into Figure 6. Eggs (bottom two cells) and larva they leave the nest and mate. The old the skin of a victim, allowing each (middle cell) are visible within nest cells; capped cells (upper right and lower left) queen dies shortly afterwards, and individual insect to sting many times. contain wasp pupae. Photo © Dennis the colony begins to die out. Only the Multiple stings by one individual Schotzko, University of Idaho new fertilized queens survive the wasp are are likely especially when winter; all workers and males die insects become trapped under with the first freezing temperatures. clothing against bare skin. Abandoned, empty nests remain in infertile (non egg-laying) females. Pain associated with stinging insects place until destroyed by weather. Males are not produced until comes not from the sting itself but September. rather from venom it delivers. STING HAZARDS Wasp and bee venoms are complex It is important to know that spring mixtures of proteins and other weather largely determines if we will “Sting” and “bite” commonly—but organic chemicals. Some venom have wasp problems or not in any incorrectly—are used as equivalent chemicals cause intense pain, others given year. Cold, rainy weather terms. Some wasps do bite; they defend kill cells and cause swelling, and still during April and May reduces the themselves by nipping at attackers other chemicals spread venom likelihood that queens can build a with their jaws. But the painful welt beyond the initial sting site. nest and collect enough food to feed that results from a wasp attack her immature offspring, while warm, Most people react to sting venoms properly is called a sting, not a bite. dry weather through June enhances with moderate to intense pain, the nest success. Stinging insects deliver venom into itching, redness, and swelling their victims by means of a needle- immediately surrounding the sting SUMMER—WORKER like apparatus—the sting—located site. Usually symptoms go away WASPS ABOUND at the tip of the abdomen. without treatment in a few hours to Once the first brood of adult worker several days. Sometimes delayed wasps is produced, they assume Only female insects can sting. This is reactions—such as hot, red swelling from the queen all tasks of because the sting is an egg-laying of a leg or arm—can last a week. maintaining the nest, foraging for tube that through the course of food, and tending to larvae. The sole evolutionary time became modified Multiple simultaneous stings can function of the queen becomes egg for injecting venom. Males cannot deliver enough venom to cause toxic laying; she remains within the nest sting; they obviously lacked an egg- injury even in people not considered for the rest of the summer. A single laying structure that evolutionary “sensitive” to venom. Human deaths yellowjacket queen can lay tens of selection could alter into a sting. from mass stinging are thousands of eggs during the season. physiologically possible but Vibrations, shadows, and stings extremely rare. Yellowjacket workers that emerge Yellowjackets, bald-faced hornets, during early summer live for 16 to 32 and paper wasps are alerted into Allergic reactions to stings days; those emerging in late summer stinging by vibrations next to their Systemic (whole-body) allergic have a 10- to 20-day lifespan. nests. Dangerous attacks can occur reactions to sting venoms occur in when lawn mowers or weed 1 to 3 percent of the population and Successive generations of workers trimmers unwittingly move over cause about 50 deaths annually in the emerge throughout summer and underground nests of yellowjackets. United States. Allergic reactions to enlarge the nest. By late August or stings involve the body’s immune early September, a nest initially Visual disturbances—such as dark, response and require at least two founded by one overwintering moving silhouettes—around nest sting episodes: the first sensitizes the yellowjacket or bald-faced hornet openings also cause stinging attacks person, and the next sting causes a queen can consist of hundreds, if not by yellowjackets. Yellowjackets are dangerous over-reaction of the thousands, of living workers. more readily provoked into stinging person’s immune system. during late summer as natural foods

8 HOMEOWNER Guide to !

Venoms contain foreign proteins (antigens) that ADVICE FOR ACCIDENTAL ENCOUNTERS WITH NESTS OF cause a body to produce its own protective YELLOWJACKETS, BALD-FACED HORNETS, PAPER WASPS proteins (antibodies) called immunoglobulin E, You and your family can take several common-sense steps to or IgE. After the first sting, the body “remembers” reduce unintentional contacts with foraging wasps and colony the venom and more quickly produces IgE. nests, including: Venom antigens bind together with IgE antibodies, causing body tissues to release Walk backwards/move slowly. If you have not agitated the histamines into the blood stream. insects into attack, calmly walk backwards from the nest, keeping your eyes on the nest in case you need to take evasive action. Histamines cause blood vessels to open wider, Move slowly because wasps especially respond to rapidly moving capillary walls to become more permeable to dark silhouettes. fluids (so as to flush the venom away), and lung air passages to constrict. For most people, the Flick, don’t swat, don’t crush bodies. Do not swat at flying reaction to histamines is local swelling and workers; they will release air-borne chemicals—called alarm itching around the sting site. pheromones—that stimulate a stinging attack from other workers. If a wasp lands on you, flick it away with your finger. Never crush Hypersensitive allergic people release large the bodies of workers, especially near the nest; crushing also amounts of histamine all at once throughout their releases alarm pheromones that induce a mass attack. entire body, lowering their blood pressure and causing respiratory distress. Hypersensitization to If you hear loud buzzing, RUN! But NOT to trees or shrubs. If you venom proteins only requires a single sting. “Hay hear loud buzzing or if you already have been stung, run quickly fever” allergens do not sensitize people to wasp or away from the nest, covering your eyes, nose, and mouth with bee venoms. your hands or shirt for protection from stings. Take shelter in a building or vehicle, or keep running until wasps stop their pursuit. Sting venoms of yellowjackets, bald-faced hornets, Agitated yellowjackets may chase you several hundred feet. and paper wasps share enough chemical Brushy trees or shrubs are not safe shelters because you can be similarities that some people have allergic surrounded and trapped by stinging insects. cross-reactions to all these species. Venoms of yellowjacket and bald-faced hornets (Vespula and FIRST AID FOR STINGS Dolichovespula species) more closely resemble Always consult your physician about pain medicines and other each other than venoms of paper wasps (Polistes first-aid advice; the information presented here does not substi- species). People sensitive to yellowjackets tute for professional medical recommendations. especially should be careful around hornets and vice versa. Immediately seek physician or medical emergency services if the victim Honey bee venom differs enough from these other stinging insects to generate its own IgE • Is stung around the head and neck or inside the mouth allergic reaction, so even hypersensitive people • Is stung several times usually—but not always—are only allergic to • Already has been stung during the previous week honey bees or only to yellowjackets, hornets, and • Is very young or very old paper wasps. Anyone who ever has suffered a • Cannot breathe easily, has difficulty swallowing, or feels dizzy severe allergic reaction to stinging insects • Develops hives that spread over the body or has a very large should consult with his/her physician about swollen welt allergen testing and venom desensitizing • Has a known hypersensitivity to stings immunotherapy. STING RELIEF STRATEGIES • Apply ice compresses to reduce swelling and pain. YELLOWJACKET • Try over-the-counter oral pain medicines and antihistamines, MANAGEMENT STRATEGIES which may provide relief from pain and itching.

Even though yellowjackets and their relatives are • Wash the sting area with soap to reduce the chances of beneficial insects, they can pose dangers when subsequent infection. Confer with your physician if reddish streaks develop from the sting; this may be a sign of nest placement or worker feeding habits put these secondary infection. insects in close proximity to people. Reducing sting probability around the home often is a matter of avoiding places where encounters are likely and eliminating foods that attract these insects to backyards.

Yellowjackets, Bald-Faced Hornets, and Paper Wasps 9 Colony destruction—a last no research data are available to • Replace late-flowering landscape resort. Colony destruction is a last support these claims. At least one plants around decks and patios resort for nests in places where commercial product line of plastic with non-flowering ornamentals. people routinely visit. Nests in picnic tablecloths and trash bags DESTROY EARLY-SEASON AERIAL secluded spots at safe distances from (BugAWAY!) impregnated with NESTS IN PROBLEM AREAS human activities do not necessarily citronella, geranium oil, rosemary, During April and May, while nest size require control action. Those nests and peppermint is marketed as is small and colonies consist of a can be left to naturally die out during repelling wasps and other nuisance lone founding queen (Figure 7), fall. insects. you can dislodge the aerial nests of PERSONAL PROTECTION Commercial mosquito/tick yellowjackets, bald-faced hornets, You and your family can take several repellants don’t work against and paper wasps by forcefully common-sense steps to reduce stinging insects. Indeed, it is spraying with a garden hose. unintentional contacts with foraging possible that the scents of some This simple tactic is most effective wasps and colony nests. products attract yellowjackets and during cool rainy weather when the other wasps. • Minimize use of perfumes, queen cannot quickly start another colognes, soaps, or other scented REDUCE ACCESS TO FOOD nest. Watch the general nest site to body lotions when yellowjackets, AND WATER see if the queen returns and tries to bald-faced hornets, and paper To minimize numbers of wasps construct a replacement nest. wasps can be expected; these foraging for sugary liquids, meats, You can safely dislodge early-season scents can be highly attractive to and other resources near people paper wasp nests anytime the queen foraging wasps. and picnics: is foraging off-site and not visible on • Wear white or tan clothes rather • Cover serving dishes at outdoor the open comb. But only approach than light blues or bright pinks, picnics; clean up spilled drinks and the closed nests of aerial reds, and oranges; close-fitting food scraps; clear away dirty plates. yellowjackets and bald-faced hornets shirts and pants are better than at night when temperatures are cool; • Do not leave soft drink cans loose-fitting clothes because wasps flight activity will be minimal and or beer bottles open and are less likely to become acci- sting hazard reduced. Stand away at unattended; yellowjackets can dentally trapped against the skin. a safe distance. crawl unseen into opened • Look for foraging workers containers and sting painfully Never physically knock down, cut- before reaching unseen when around the mouth. and-bag, or otherwise disturb large picking caneberries (raspberries, nests. The sting hazard is too high. • Keep lids on trashcans and blackberries), grapes, and tree dumpsters; clean to remove Subterranean nests. Nests of fruits such as apples, peaches, and attractive odors or use disposable ground-dwelling yellowjackets are pears; these can be highly can liners; rinse cans and bottles more difficult to physically destroy attractive to yellowjackets. before placing in outdoor recycling than above-ground nests. For one • Inspect for nests before doing bins. thing, early-season subterranean yard work and home maintenance nests are hard to find. By the time • Move food garbage away from during mid-to-late summer, you notice flight activity around nest patios or places where people especially when trimming hedges, entrances, colonies probably have congregate. mowing dry overgrown weedy grown to dangerous sizes that defy areas, weeding rock gardens, or • Don’t leave moist pet foods outside. physical destruction. working around eaves and roofs. • Control infestations of aphids Flooding rarely works. Some • Wear leather gloves if you must and scale insects that produce people recommend flooding reach into likely nest sites. honeydew on landscape trees underground nests with a garden and shrubs. hose or even pouring boiling water • Teach children to stay away into nest openings. But unless the from (and to tell an adult about) • Eliminate drips from faucets, nest is located directly below the any nests they discover. sprinklers, and garden hoses, opening, neither method is effective. especially during the dry parts • Don’t block the return flights of Depending on landscape terrain, the of the summer. Puddled water foraging workers by standing in actual nest combs may be located attracts workers. front of nests; workers may above the surface entrance or interpret your presence as a threat. • Clean up rotting apples and distantly located from the entrance peaches that fall from trees; pick and so escape destruction. REPELLANTS caneberries before they over-ripen. Covering nest entrances with soil Mint oil and other plant oils are said is not effective; trapped wasps to repel yellowjacket workers, but will dig new exits.

10 HOMEOWNER Guide to Figure 7. Bald-faced hornet queen begins springtime nest construction. Reduce sting hazard by destroying early-season nests in problem areas while the colony consists solely of the overwintering queen. Photo from Ken Gray slide collection, Oregon State University

Never pour kerosene or gasoline into subterranean nests. This practice poses high hazard of explosive fires plus soil contamination and groundwater pollution. Figure 8. Yellowjacket trap is hung too close to a site frequented by people. This incorrect trap placement can increase sting threat by drawing wasps to the area. Photo by Edward Bechinski Vacuum removal is a job for pros. Nest removal by vacuuming is effective, especially in sensitive areas where insecticides containers baited with meats, sugary all the nests that potentially occur cannot be used. But vacuuming is foods, or synthetic chemicals that within that range. Theoretically, one too hazardous for homeowners. smell like food. could eliminate yellowjacket nests in Contact a local professional pest a single yard by trapping the initial Yellowjacket traps do not capture management company for such overwintering queen during the paper wasps. Paper wasps primarily services. spring, but this would not stop feed on living prey and so do not problems from nests surviving Fall-winter nest removal respond to the same odors as beyond an individual yard. Research Eliminating aerial or subterranean yellowjackets. Traps can temporarily shows that overwintering queens are nests during fall and winter months reduce nuisance problems by notoriously unresponsive to traps. has no impact on populations the attracting yellowjacket workers next year because wasps neither away from patios or other backyard About commercial traps overwinter in old nests nor re-use areas where people congregate. Commercial traps include both them the following spring. Still, it is a Four to six traps hung around the baited and unbaited devices as well good practice to destroy large perimeter of the yard at least 20 feet as disposable and re-usable designs abandoned aerial nests attached to away from people are enough for (Figure 9). Traps baited with a fruity- homes. Old nests can shelter most home yards. Don’t hang traps smelling synthetic attractant named earwigs, carpet beetles, and other on your patio deck or other places heptyl butyrate are highly attractive potential insect pests. where people congregate (Figure 8); to our most common species, the traps placed where people gather western yellowjacket, but are less TRAPPING NUISANCE may increase sting hazard by attractive to the common YELLOWJACKETS attracting even more yellowjackets yellowjacket and the German Uses and limitations than otherwise would be present. yellowjacket. Yellowjackets readily can be Traps capture impressive numbers of Table 1 on page 13 summarizes captured and killed in a variety of yellowjackets but do not eliminate features of some widely-available commercial and home-made traps. colonies. Workers commonly forage commercial traps and their All traps work on the same principle: several hundred yards from their attractants. yellowjacket workers that scavenge nest and are known to fly 3/4 mile in for non-living protein and carbo- Unbaited traps require that you add search of food. It is not possible to hydrate foods are captured inside protein and carbohydrate foods. Baits entirely trap-out every worker from

Yellowjackets, Bald-Faced Hornets, and Paper Wasps 11 !

POISONED FOOD BAITS ARE HAZARDOUS AND ILLEGAL

It is illegal and highly hazardous to make poisoned baits for yellowjackets by lacing foods with insecticides. There are no insecticides that legally may be added to yellowjacket food attractants.

Prior to 2002, homeowners legally could add an insecticide called Knox-Out 2FM to protein food baits. Foraging yellowjacket workers would carry these baits back to their nests and poison the entire colony. Knox-Out insecticide was removed from the market without replacement during 2002.

Out-of-date recommendations Figure 9. A variety of yellowjacket traps are widely available from retail stores for backyard about home-made poison baits use. Photo by author Edward Bechinski readily can be found by Internet searches, but all violate federal and state pesticide law. like canned, fishy cat food, luncheon Place natural food baits in a meats, and fruit juices attract small disposable drinking cup yellowjackets, but usually not as located inside the bottom piece many as synthetic heptyl butyrate. of the bottle. Invert the top piece much that homeowners can do to into the larger bottom part so enhance the impact of these Natural food baits must be replaced at that it makes a funnel, and then least every other day during the heat naturally-occurring enemies of secure the two pieces with tape. of summer so they stay moist but do yellowjackets. Nor are there any not spoil. Citrus-flavored carbonated Add an inch of soapy water biological control agents that can be soft drinks (eg., Mountain Dew, in the bottle to drown trapped purchased for mass release. Minute Maid Orange Soda) have yellowjackets. Commercially available microscopic- proven highly attractive to German Yellowjackets respond to food odors size predatory nematodes potentially yellowjackets in the midwest. from the trap by crawling through could be applied as drenches to Disposable traps. Disposable traps the opening in the inverted top. Once subterranean yellowjacket nests. But reduce sting hazard by eliminating inside the cylindrical bottom piece, because it takes days for lethal any need to handle traps containing most yellowjackets will not be able infections to develop, application live yellowjackets. Re-usable traps to find their way back through the would be limited to yellowjacket periodically must be emptied and re- funnel opening. nests where slow-to-develop, partial provisioned with food baits or reductions in colonies are You can make another simple chemical lures. Some re-usable traps acceptable. California research trap by hanging a chunk of fish or directly kill captured insects by meat by a string an inch or so above showed some nests recovered even drowning them in soapy water while a dishpan filled with soapy water. when massive volumes (2 gallons) of other traps restrain living Yellowjackets feeding on the bait nematodes were injected directly yellowjackets until they die. occasionally bite off more than they into nests that had been exposed Make your own yellowjacket can carry back to the nest so fall into by digging away soil. trap. You can construct your own the water and drown. Extreme sting hazard during yellowjacket traps from large BIOLOGICAL CONTROL—NOT MUCH application further argues against (2-liter) plastic soft drink bottles. FOR HOMEOWNERS nematode drenches. Effective Cut horizontally through the A surprisingly diverse community of control of aerial nests with nematode bottle 4 or 5 inches below the top. predators, parasitoids, and pathogens suspensions seems unlikely because prey on yellowjackets and their nematodes are aquatic organisms relatives. Unfortunately there is not and would quickly dry out and die.

12 HOMEOWNER Guide to INSECTICIDES names. You always can find the where sting hazard is high. Active nests of yellowjackets, bald- common names of active ingredients Treatment of trees, shrubs, and other faced hornets, and paper wasps by reading the label on the pesticide yard and garden plants at best only located in areas where people container. Every pest-killing temporarily reduces wasp presence. routinely pass may justify insecticide chemical will be listed on the label Many repeated applications to treatment. Choosing the right under the section marked "active landscape plants would be required. ingredients." insecticide can be confusing because IMPORTANT. Unless the label the same insect-killing chemical We do not recommend insecticide specifically says the insecticide can typically is sold under dozens of application to landscape plants be used for yellowjackets, hornets, or different retail trade names. Here we where yellowjackets and related wasps outside around residential discuss products by the name of the wasps are foraging for food; we only yards and gardens, you have the insect-killing active ingredient rather advise direct treatment of active wrong product. Many products are than by their many retail trade nests around doors or other places intended for use only outdoors; never

Table 1. Commercial traps and attractants for yellowjackets: Traps that use heptyl butyrate are highly attractive to our most common species, the western yellowjacket.

COMMERCIAL PRODUCT COMPONENTS ATTRACTANT*

Advantage Yellow Jacket Trap for Southern, bucket trap + liquid attractant vinegar Eastern, Common, German Yellowjacket

ADVANTAGE Yellow Jacket Trap for Western bucket trap + liquid attractant heptyl butyrate Yellowjackets

Oak Stump Farms Yellow Jacket bucket trap + liquid attractant heptyl butyrate and Wasp Trap (protein + carbohydrate baits to be added by homeowner) Oak Stump Farms Yellow Jacket liquid attractant refill heptyl butyrate and Wasp Lure

Raid Disposable Yellow Jacket Trap bucket-type trap + liquid attractant confidential**

Rescue Yellowjacket Trap cone/funnel trap + attractant heptyl butyrate Rescue Yellowjacket Trap Attractant (4-wk) liquid attractant refill heptyl butyrate Rescue Yellowjacket Trap Cartridge (10-wk) liquid attractant cartridge heptyl butyrate

Safer Deluxe Yellowjacket/Wasp Trap bucket/funnel trap + liquid attractant heptyl butyrate

Victor Yellow Jacket Magnet disposable bag trap + liquid attractant fruit juice concentrate Victor Yellow Jacket & Flying Insect Trap reusable jar trap + liquid attractant fruit juice concentrate Victor Yellow Jacket Trap Bait liquid attractant refill fruit juice concentrate

Xcaliber Reusable Yellow Jacket Trap bucket trap + liquid attractant heptyl butyrate Xcaliber Disposable Yellow Jacket Trap bag trap + liquid attractant heptyl butyrate Xcaliber Reusable Yellow Jacket Bait liquid attractant refill heptyl butyrate

TABLE NOTES * Reference source: Material Safety Data Sheets and personal communication (P. Landolt USDA) ** Non-toxic plant-based attractant not specifically identified by manufacturer

Yellowjackets, Bald-Faced Hornets, and Paper Wasps 13 ! use these inside buildings. SAFETY PRECAUTIONS BEFORE YOU SPRAY Selection of the best product for out-of-doors nest treatment Follow these precautions if you decide to spray a around home landscapes depends on balancing human safety yellowjacket, bald-faced hornet, or paper wasp nest: with control effectiveness. • Inspect the nest. Inspect the colony from a safe HUMAN TOXICITY CONSIDERATIONS distance (at least 10 feet) during the day so that Conventional insecticides interfere with the nervous you know exactly where the nest entrance of system. The insect-killing active ingredients in almost all yellowjackets or bald-faced hornets is located off-the-shelf hornet and wasp insecticides are one of two types: before you spray. DO NOT SPRAY unless you can pyrethrin and pyrethroids. Pyrethrin is a natural insect-killing see the entrance; otherwise, you will be stung by chemical extracted from chrysanthemum flowers, while insects that escape contact with the killing spray. pyrethroids are human-synthesized compounds similar in • Only spray nests after dark. Wasps are less active chemical structure to natural pyrethrin. Both are widely used after dark in cool temperatures, and most (but not because of their quick knock-down, meaning that they rapidly all) foraging workers will be present in the nest. paralyze the insect. • Do not shine a flashlight directly at the nest. You Both natural pyrethrin and human-synthesized pyrethroids are may provoke an attack. Do not hold the flashlight nerve poisons—they kill by interfering with the nervous in your hand; agitated wasps will fly to the light. system—and so pose at least some hazard to humans, pets, Illuminate the nest from the side or back with a and wildlife via accidental exposure. light placed on the ground some distance from where you will be standing. Virtually all conventional wasp and hornet insecticides for homeowners are considered by the U.S. Environmental • Wear heavy clothes and eye protection. Protect Protection Agency (EPA) as only slightly toxic to people. yourself from stings by wearing heavy clothing, You can judge the relative toxicity of any pesticide to people by a hat, and goggles or other eye protection; some looking for one of the following special “signal words” printed yellowjackets temporarily blind victims by spraying on the pesticide label: venom from their sting into the eyes. • CAUTION designates "slightly toxic" products; this is the • Take care when spraying around sensitive areas lowest (least toxic) pesticide category. like vegetable gardens, pet kennels, and windows. Some wasp and hornet killers specifically prohibit • WARNING A few of the more concentrated wasp-killers are application to plant foliage. NEVER EAT any classified by EPA as moderately toxic; these products always vegetables or fruits that might have accidentally say "warning" on the pesticide label and are toxic to people at been sprayed. smaller doses than pesticides that say Caution on the label • Contract with a professional pest control operator • DANGER None of the retail wasp insecticides for when dealing with: homeowners carries the signal word "danger" that designates highly corrosive pesticides that can permanently injure eyes Large aerial nests of hornets or burn skin. Late-summer nests of ground-dwelling yellowjackets Low-risk insecticides German yellowjackets in home wall voids Insect-killing chemicals in two products—the EcoEXEMPT product line and Victor Poison-Free Wasp & Hornet Killer— Nests in attic spaces where potential escape generally are considered by EPA as entirely safe for people. from stinging attack is limited. These types of These products contain naturally-occurring plant oils (clove nests can house dangerous numbers of workers oil, phenylethyl proprionate, peppermint, rosemary, or that pose high sting hazards. wintergreen oils) that are eaten by people in foods and so pose Nests in wall voids present an additional problem: no risks to people. After colonies have been killed, dead workers, CONTROL EFFECTIVENESS larvae, and nest materials must be physically CONSIDERATIONS removed from the wall void; otherwise, they generate an intolerable rotting stench. Wet vs. dry insecticides The most useful homeowner products for treating outdoor nests of yellowjackets, bald-faced hornets, and paper wasps are the ready-to-use aerosol jet sprays and liquid pump-trigger sprays that propel insecticidal streams or foaming sprays 20 feet or more into nests (Figure 10). These are especially useful for treating small aerial nests (golf ball size or smaller) that contain relatively few individuals. Treat underground nests of

14 HOMEOWNER Guide to yellowjackets with ample volumes of liquid insecticides that penetrate and saturate the entire colony. Only a few dry-dust insecticides are available; these are best suited for yellowjacket nests in wall voids. The labels of some granular insecticides list stinging insects as pests controlled. Although these products would kill insects that contact a granule, sprays are better choices. Knock-down vs. residual killing action. Some wasp and hornet killers combine an especially quick-acting but short-lived pyrethroid insecticide (or natural pyrethrin) with a longer- lasting pyrethroid insecticide. The first ingredient immediately paralyzes the insect but lasts less than a day Figure 10. Ready-to-use aerosol jet-sprays and liquid pump-trigger sprays are suited for direct before degrading into inactive application to wasp nests. Photo by Edward Bechinski chemicals. The second insecticide lasts a few days to several weeks and kills any returning foraging workers Treating above-ground nests safe distance for workers flying in that later return to the nest. These For aerial yellowjackets and bald- and out of the entrance. Don’t combination products often are faced hornets, direct the insecticide approach too closely because you labeled "quick knockdown” and stream into the nest entrance. For may provoke attacks from "residual kill." paper wasps, spray across the surface yellowjacket workers that guard the of exposed nest comb. Foaming spray entrance. Mark the area and come Short-residual pyrethroid insecticides insecticides are especially effective back after dark to treat the nest. for yellowjackets, bald-faced hornets, against paper wasps. and paper wasps include allethrin, Direct the insecticide stream into the bioallethrin, bioresmethrin, Spray until nests are soaked. Leave opening of subterranean yellowjacket phenothrin, resmethrin, sumithrin, treated nests in place for a day or nests. You can plug the entrance hole and tetramethrin. Again, these names two; not all workers return to the with soil after treatment to seal are the active ingredients that kill the nest at night, so any workers foraging workers inside, but be sure to spray insects; each active ingredient is away from the nest during spray the soil plug to kill any foraging available in many different application will be killed by workers that later return to the nest. insecticide residues when they return commercial trade-name products. By Treating yellowjacket nests in to the nest. Scrape off dead nests themselves, these chemicals—as well wall voids. Leave to professionals from buildings after two days so that as natural pyrethrin—may not both insecticide application and they do not discolor exterior provide satisfactory control; any subsequent nest removal. But if you surfaces. workers that had been foraging away do decide to apply your own from the nest during pesticide Treating below-ground treatments, use aerosols or dusts that application eventually will return and yellowjacket nests. Locating can be blown into the entire expanse remain agitated around the nest site subterranean nests of soil-nesting of the nest. After application, plug for several days. yellowjackets requires patience. First, the nest opening with fiberglass Longer-lasting pyrethroid insecticides bait the yellowjackets with cat food building insulation; treat the plug for yellowjackets, bald-faced hornets, or tuna fish, and then watch an with insecticide to kill any foraging and paper wasps include beta- individual wasp as it flies back to its workers that later return. nest with scavenged food. Foraging cyfluthrin, bifenthrin, cyfluthrin, Never plug nest entrances as an yellowjacket workers generally fly in lamda-cyhalothrin, deltamethrin, alternative to insecticide application. a straight line back to their nest. permethrin, and tralomethrin. These Trapped workers can chew a new provide excellent control by Then go to where you lost sight of the opening through interior walls and themselves as well as in ready-to-use insect, wait until another flies by, and emerge in mass into living quarters. mixtures with short-residual repeat the process until you see the ingredients. nest hole in the ground. Look from a

Yellowjackets, Bald-Faced Hornets, and Paper Wasps 15 TO ORDER For more copies of this publication, or to order BUL 854 Homeowner Guide to Bees or BUL 853 Homeowner Guide to Minor Stinging Insects, contact the University of Idaho College of Agricultural and Life Sciences Publications Warehouse at (208) 885-7982, or e-mail [email protected]. To download these publications for free, go to http://info.ag.uidaho.edu:591/catalog/default.htm and select insect pollinators.

ABOUT THE AUTHORS EDWARD BECHINSKI is a University of Idaho professor of entomology and coordinator of pest management for University of Idaho Extension; contact him at (208) 885-5972 or [email protected]. FRANK MERICKEL is manager of the University of Idaho College of Agricultural and Life Sciences Barr Entomological Museum; contact him at (208) 885-7079, or [email protected]. LYNDSIE STOLTMAN is graduate research assistant. HUGH HOMAN is University of Idaho professor emeritus of entomology. All are with the Division of Entomology.

PESTICIDES DISCLAIMER ALWAYS read and follow the instructions printed on the pesticide label. The pesticide recommendations in this UI publication do not substitute for instructions on the label. Due to constantly changing pesticide laws and labels, some pesticides may have been cancelled or had certain uses prohibited. Use pesticides with care. Do not use a pesticide unless both the pest and the plant, animal, or other application site are specifically listed on the label. Store pesticides in their original containers and keep them out of the reach of children, pets, and livestock. Trade names are used to simplify the information; no endorsement or discrimination is intended.

Pesticide Residues Any recommendations for use are based on currently available labels for each pesticide listed. If followed carefully, residues should not exceed the established tolerances. To avoid excessive residues, follow label directions carefully with respect to rate, number of applications, and minimum interval between application and reentry or harvest.

Groundwater To protect groundwater, when there is a choice of pesticides, the applicator should use the product least likely to leach.

Issued in furtherance of cooperative extension work in agriculture and home economics, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Charlotte V. Eberlein, Director of University of Idaho Extension, University of Idaho, Moscow, Idaho 83844. The University of Idaho provides equal opportunity in education and employment on the basis of race, color, national origin, religion, sex, sexual orientation, age, disability, or status as a disabled veteran or Vietnam-era veteran, as required by state and federal laws.