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Yellowjackets , Bald-Faced Hornets , and Paper Wasps HOMEOWNER Guide to by Edward Bechinski, Frank Merickel, Lyndsie Stoltman, and Hugh Homan BUL 852

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Yellowjacket

Bald-Faced Hornet

and Paper Wasp

HOMEOWNER Guide to by Edward Bechinski, Frank Merickel, Lyndsie Stoltman, and Hugh Homan BU

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2 HOMEOWNERGuide to

“ . . . spring weather largely

determines if we will have wasp

problems or not in any given year.

Cold, rainy weather during April

and M ay reduces the likelihood”

TABLE OF CONTENTS

I. IDENTIFICATION . . . . . . . . . . . . . . . . . . . . . . . . . .3 - 7 Yellowjackets . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

Western . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

Common . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4German . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5Aerial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

Bald-faced hornets . . . . . . . . . . . . . . . . . . . . . . . . .6Paper wasps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

II. SEASONAL LIFE CYCLE . . . . . . . . . . . . . . . . . . . . . .7Box: Saving Nests . . . . . . . . . . . . . . . . . . . . . . . . . .7

III. STING HAZARDSLocalized, toxic and allergic reactions . . . . . . . . . . .8Box: Advice for encounters . . . . . . . . . . . . . . . . . . .9

IV. MANAGEMENT STRATEGIES . . . . . . . . . . . . . . . . . . .9Personal protection . . . . . . . . . . . . . . . . . . . . . . . .10Repellants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

Reduce access to food and water . . . . . . . . . . . . .10Nest destruction . . . . . . . . . . . . . . . . . . . . . . . . . .10 Traps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11Biological control . . . . . . . . . . . . . . . . . . . . . . . . . .12Box: Poison bait . . . . . . . . . . . . . . . . . . . . . . . . . .12 Table 1 Commercial traps, attractants . . . . . . . . . .13Insecticides

How to select the right product . . . . . . . . . . . . . .13Box: Safety precautions before you spray . . . . . .14

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 Yellowjackets, Bald-Faced Hornets, and Paper Wasps   3

WESTERN YELLOWJACKET, Vespula pensyl- vanica, Idaho’s most abundant species, buildsunderground nests in abandoned animal bur-rows, hollows under sidewalks, and crevices inretaining walls. Papery nests: Underground.

Picnic pest: Yes.Photo from www.worsleyschool.net 

COMM ON YELLOWJACKET, Vespula vulgaris ,also builds underground nests around theyard. It feeds on insects but scavenges frompicnics as insect prey becomes scarce.Papery nests: Underground. Picnic pest: Yes.

Photo ©Neil Miller/ Papilio/Corbis

AERIAL YELLOWJACKET, Dolichovespulaarenaria, mostly builds nests above ground

that can grow to impressive sizes. Paperynests: Builds nests both underground andabove ground on roof overhangs or onprotected building surfaces. Picnic pest:Not usually. Photo ©Craig Persel

PAPER WASPS,  Polistes, in color are similarto yellowjackets, but they have a slimmer,elongated body shape and a long-leggedappearance. Legs hang down even duringflight. Papery nests: Resemble an openumbrella with individual comb cells opento view from below. Picnic pest: No.Photo ©Dennis Schotzko, University of Idaho

BALD-FACED HORNETS, Dolichovespulamaculata, are heavy-bodied, black-coloredwasps with pale yellow-white marks on thehead and at the end of the abdomen. Paperynests: Often high in trees or at roof peaks;soccer-ball-sized nest is not unusual by fall.Picnic pest: Little risk. They’re not aggressive.Photo ©Dennis Schotzko, University of Idaho

GERMAN YELLOWJACKET, Vespulagermanica, an aggressive scavenger of meats

and sweet drinks, poses high sting hazard. Itmay survive Idaho winters when nesting in wallvoids and home attics. Papery nests: In homewall voids and in attics. Picnic pest:  Yes.Photo ©Andy Wehrle/ bugguide.net 

YELLOWJACKETS—WASPS IN THE VESPULAOR DOLICHOVESPULA GENERA—UNLIKEBEES—ARE SHINY AND BARE OF HAIR. THEY’RE ALSO SLEEKER THAN BEES. OF 11SPECIES FOUND IN IDAHO, THESE FOUR ARE THE MOST COMMON. ALL CAN STINGMULTIPLE TIMES.

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4 HOMEOWNER Guide to

IDENTIFICATION The words bee, wasp, yellowjacket,and hornet often are usedinterchangeably—but incorrectly—todescribe any medium-to-large, yellow-and-black stinging insect.Beeis abroad term that describes a diversegroup of insects whose body is at leastpartly covered in fine hairs.Waspsdiffer physically from bees in that theirbodies are almost bare and shiny.

 Yellowjacket technically only refersto wasps in the scientific generaVespula orDoli chovespula . Names areeven more confusing becausehornetis used informally in the United Statesto describe certain large species of Doli chovespula yellowjackets thatbuild aerial nests. Biologicallyspeaking, the only true hornets aremembers of a still different genus,Vespa , none of which occurs in Idaho

or any adjoining western state.

 Yellowjackets and their commonlyencountered relatives—the bald-facedhornet and paper wasps—aresocial wasps. They live as a singlereproductive female (the queen) andher infertile female offspring (theworkers) in a central nest where

they cooperatively rear and vigorouslydefend their immatures.

TRIO OF PAPERY NEST BUILDERS Yellowjackets, bald-faced hornets, andpaper wasps all build grey-to-tanpapery nests of fibers chewed fromweathered wood. Adult wasps oftencan be seen around yards, gnawing

pulp from backyard fences, firewood,and even cardboard stacked outsidefor recycling. Nests consist of hexagonal-shaped cells arrangedside-by-side into horizontal layersof comb. Nest shape, size, andplacement distinctly differ amongthese three major insect groups. These differences are explained inthe following sections.

YELLOWJACKETS—4 SPECIESPOSE STING HAZARDS NEARIDAHO HOMES

 Yellowjackets are medium size(about 1/2-inch long) black waspsmarked with irregular, jagged yellowbands. They become pests at picnicsand other outdoor settings wheremeats and sugary drinks are present(Figure 1).

Eleven different species of yellowjackets are known in Idaho,but normally only four species posesting hazards that sometimes justifycontrol action: (See photos on p. 3.)

• western yellowjacket

Vespula pensylvani ca 

• common yellowjacketVespula vulgari s 

• German yellowjacketVespula germani ca 

• aerial yellowjacketDolichovespula ar enar i a 

Species identification requires expertexamination but is not necessary todecide if control action is needed.

 Thewestern yellowjacketis ourmost abundant species. It sharesmany biological features with anotherfrequently encountered species, thecommon yellowjacket. Both are

native to Idaho. Their natural habitatis dry grass and wooded areas, butthey readily nest around homelandscapes.

 These two yellowjackets almostalways build subterranean nestshidden from view within naturalcavities (Figures 2, 3a, 3b). Typicalbackyard nest sites includeabandoned animal burrows, hollowsunder sidewalks, and crevices inlandscape retaining walls. In forestedareas, these two yellowjackets build

nests within fallen logs, old stumps,and in the soil.

YELLOWJACKETS EAT INSECTS,MEAT, SWEET NECTARUnlike honey bees, yellowjackets donot produce honey, nor do they storefloral nectar in nest cells. Thewestern yellowjacket and thecommon yellowjacket primarilyfeed as predators on living insects,especially during the spring andearly summer. Workers searchout caterpillars, beetle grubs,grasshoppers, flies, spiders, andother soft-bodied prey, which theyreturn to the nest as chewed-upfood for their own developing larvae. Yellowjacket workers kill prey bybiting, not stinging. Adultyellowjackets themselves ingestsome body liquids from prey butmainly feed on plant nectar. Workers

 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.

Photo ©Terry Thormin/Royal Alberta Museum

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 Yellowjackets, Bald-Faced Hornets, and Paper Wasps   5

also feed mouth-to-mouth on liquids produced bytheir larvae. As summer progresses and insectprey becomes scarce, western and commonyellowjackets increasingly feed as scavengers onnon-living proteinaceous (protein) and sugaryfoods.

Workers naturally feed on carrion, nectar, andhoneydew (the sugary liquid secreted by aphidsand scale insects). Landscape trees with yellow- jackets flying about during late July and Augustusually indicate the trees are infested with honey-dew-producing aphids or scale insects.

Scavenging feeding behavior increases humansting hazard because it places yellowjackets inclose contact with people.

Meats and carbohydrate drinks at picnics or insidegarbage cans attract large numbers of yellowjackets that readily sting. Overripe fruit thatfall from backyard fruit trees also attract large

numbers of foraging workers.GERMAN YELLOWJACKETIN IDAHO SINCE 19 80 S The German yellowjacket is a European speciesfirst recorded in the northeast U.S. during the1970s and subsequently in Idaho during the 1980s.It poses a high sting hazard to people because it isanother aggressive scavenger of meats and sweets(as well as a voracious predator of living insects). The sting hazards posed by the common, thewestern, and the German yellowjackets haveclosed school playgrounds and resorts, curtailedlogging operations, and interfered withcommercial fruit harvest.

 The German yellowjacket can be a specialpest problem because it sometimes buildsnests in wall voids and attics of homes. Otheryellowjackets naturally die out with cool falltemperatures, but the nesting habits of Germanyellowjackets potentially allow colonies to persistyear-round in the mildest areas of Idaho.

AERIAL YELLOWJACKET MAKESABOVE-GROUND NESTS The other frequently encountered species is theaerial yellowjacket. It mostly builds nests aboveground, although below-ground nests are notunusual. The above-ground nests are similar inform to subterranean nests of the common,western, and German yellowjackets. Nests consistof layers of papery comb wrapped by an outerenvelope with an entry hole. Nests occur fromground-level to tree-top heights on all types of vegetation.

Aerial yellowjackets also commonly build nestsfrom roof overhangs or other protected exteriorsurfaces of buildings. Nests grow to impressive

Figure 1. Yellowjacket workersscavenge food from meatscraps. Photo ©WhitneyCranshaw, Colorado StateUniversity,www.insectimages.org 

Figure 2. Yellowjacket workershover near opening to nestlocated in hidden cavity behindbrick wall. Photo ©WhitneyCranshaw, Colorado StateUniversity,www.insectimages.org 

Figure 3 a. Cross-section of atypical subterranean yellowjack-et nest hanging within an

underground cavity shows tiersof horizontal comb where imma-ture life-stages are reared byworkers. Worker yellowjacketscrawl down soil cavity and enternest through an opening at thebottom of the outer wall. Figurefrom Akre et al. 1980 USDAAgriculture Handbook 552 

Figure 3 b. Compare diagram-matic illustration 3a with actualyellowjacket nest exposed by

digging away surrounding soil.In late season, one nest canhouse thousands of workers.Photo from Ken Gray slidecollection, Oregon StateUniversity

l  entry

l  comb tierswith cells

  louternest wall         l

nest opening

lentry

louter nest wall

  lnest opening

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6 HOMEOWNER Guide to

sizes as summer progresses and maycontain as many as 700 workers.Aerial yellowjackets normally prey onliving insects and so are not nuisancepests around picnic foods or garbagecans like the other three. An exceptionoccurs in late summer when aerial

yellowjackets are attracted to sugaryfoods. Control of aerial yellowjacketsis warranted only if people or petsroutinely pass near nests or peoplewith known allergies to wasp venomsare present.

BALD-FACED HORNETS BUILDLARGE AERIAL NESTS The bald-faced hornet,Doli chovespula maculata , is a large (3/4-inch), stout-bodied, black wasp with awhitish-yellow face and a few whitishmarks near the end of the body (see p.

3). Like the aerial yellowjacket, bald-faced hornets build enclosed, paperyabove-ground nests on landscapeplants and buildings (Figure 4).

Bald-faced hornet nests often haveleaves and twigs in the outer nest wall,whereas nests of aerial yellowjacketsdo not.

Reduced sting hazard. In spite of their large size, bald-faced hornetspose a substantially reduced stinghazard compared to yellowjackets.Bald-faced hornets almost entirely

feed on other living insects, includingyellowjackets, and so do not becomenuisances at outdoor events wherefood is served. Potential for stingingencounters also is reduced becausenests of bald-faced hornets often arelocated high in trees or at roof peaks.Workers will sting when provoked (bysomeone bumping the nest orsqueezing hornets against the skin),but are not as aggressive in defendingnests as yellowjackets.

PAPER WASPS—IDAHO’S MOSTCOMMON STINGING PESTSPaper wasps resemble yellowjacketsbut have a slimmer, elongate bodyshape with a characteristic long-leggedappearance (see p. 3). Their legs evendangle below the body in flight.

 The golden paper wasp,Poli stes fuscatus aur i fer , a yellow-to-reddish-brown wasp with yellow banding, was

the most common type of paper waspthroughout the Gem state until thelate 1990s. Although this nativespecies still occurs in rural areas of Idaho, it largely has been displacedin urban habitats byPoli stes dom- 

inu lus , the European paper wasp.

 The non-native European paper waspwas first observed in Massachusettsduring 1981. It expanded westwardreaching the Pacific Northwest

during 1999. The European paperwasp now occurs statewide in Idahoand ranks as our most commonlyencountered stinging pest.

Umbrella-shaped, open nestsPaper wasps build distinctive

umbrella-shaped paper nests(Figure 5) seen hanging upside-downfrom doorframes, eaves, and otherprotected places. Nests are open-combed, meaning cells are notenclosed by an outer envelope likenests of yellowjackets and bald-facedhornets. Individual cells can be seenwhen viewed from below (lookingup into the nest). Like yellowjacketsand hornets, paper wasps are socialinsects.

Paper wasps are beneficial predators.

 They do not scavenge on non-livingfoods as do nuisance yellowjacketsbut instead prey on caterpillars andother soft-bodied, leaf-feedinginsects. Adult paper wasps also feedon nectar, so can be seen foraging onflowers. During summer you’ll oftenfind them around your yard’s waterpuddles and ponds.

Figure 4. Bald-faced hornet nest is similar in form to subterranean yellowjacket nests butalways is located above ground, usually on landscape plants or buildings. They can get aslarge as soccer balls by early fall. Note two nest openings through the outer wall on the leftside, bottom third. Photo by University of Idaho

Figure 5. Paper wasps build nests thatresemble an open umbrella with individualcomb cells open to view from below. Photofrom Ken Gray slide collection, OregonState University

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 Yellowjackets, Bald-Faced Hornets, and Paper Wasps   7

Fairly docile.Compared withyellowjackets, European paperwasps are relatively docile. Theydon’t aggressively attack people, but

will sting to defend their nest whenprovoked. People are stung whenthey accidentally contact a hiddennest, such as inadvertently touchinga nest with a bare hand whilegardening.

European paper wasp nests—almost anywhereEuropean paper wasps are pests butnot because they aggressively sting.Unless you accidentally physicallycontact the nest itself, wasps oftenrespond to disturbance by flying

about the nest rather than stinging.However, European paper waspshave become statewide sting threatsbecause they readily build nests in just about any protected backyardsite and so frequently areencountered by people. Commonnests sites around the home include:

• Inside outdoor light fixtures,mailboxes, cable TV/home-utilityboxes, exterior door chimes,covered barbeque grills, birdhouses, and bird feeders

• Fenders, bumpers, and other

exterior surfaces of vehiclesparked for long-term storage

• Exterior walls of homes—especially those covered by ivyor other creeping vines

• Limbs and foliage of landscapeshrubs, particularly denseevergreen shrubs

• Under stone ledges in rock gardensand within crevices betweenlandscape timbers

• In home attics, wall voids, and

similar spaces where vents or holesallow wasp entry

• Under eaves, shutters, patio decks,and similar overhanging places

• Inside folded outdoor umbrellas,under seats and armrests of patiochairs, and under tables

• Within hollow-framed outdoorfurniture or hollow fencing

• On roofs under cedar-shake shingles

Other paper wasps only build neststhat hang horizontally from

protected places, but the Europeanpaper wasp also builds nestsattached vertically to protectedsurfaces. This nesting behavior,together with their high relativeabundance, places European paperwasps in routine contact withpeople.

European paper wasp nests often aregolf-ball size and consist of 20 orfewer cells. Nests with hundreds of cells are possible in the warmer partsof Idaho where hot, dry weather

allows for prolonged reproduction.

SEASONAL LIFE CYCLE

WINTER—MATED QUEENSSURVIVE OUTDOORS Yellowjackets, bald-faced hornets,and paper wasps survive Idaho

winters as solitary but mated femalescalled queens. None of these speciesoverwinters within their nests. Thesereproductive female wasps insteadoverwinter outdoors under loose treebark or on the ground in weedy areasthat provide cover.

An exception to outdoorsoverwintering is the golden paperwasp, which sometimes overwintersin home attics or other unheatedparts of buildings. They can becomestinging pests inside homes duringlate winter when sunny days raisetemperatures in attic spaces, andwasps escape into household livingquarters. Wasps flying aroundwindows inside Idaho homes duringwinter usually arePoli stes paperwasps.

SPRING—NESTBUILDING;WEATHER DETERMINESWASP PROBLEMSOverwintering queens emerge fromhibernation during the first warmdays of spring in March and April. They immediately begin to feed onnectar and readily can be observedaround home landscapes onflowering plants or at water sources.

 Yellowjackets, bald-faced hornets,and paper wasps build new nestseach spring. None re-uses nests from

year to year. Yellowjackets and bald-faced hornets work as individualqueens to construct their own nest.European paper wasps sometimeswork together as cooperatingoverwintering queens to make asingle shared nest.

In all of these species, the queen laysa single egg in each cell. Eggs hatchinto small, legless, whitish grubs,each occupying one cell in the comb(Figure 6). The queen cares for herlarvae by feeding them chewed-upinsects that she captures frombackyard plants.

Grubs develop through severalsuccessively bigger stages, eventuallytransforming into pupae andemerging as adult worker waspsabout one month after eggs are laid.Workers are entirely comprised of 

!SAVING YELLOWJACKET AND

BALD-FACED HORNET NESTS

 The large papery nests that

aerial yellowjackets and

bald-faced hornets build in

landscape trees and shrubs

can be brought into homessafely during late fall as indoor

decorations or curiosities.

On cool November days,

clip abandoned nests from

branches, then bag and place

in the freezer one or two days.

Freezing kills any remaining

workers or other insects—like

earwigs—that sometimes live in

old nests. Physically shake any

dead insects and other debris

from the nest; otherwise, nests

can become an odor problem. You could wait until the hard

freezing days of winter to

collect the nest, but papery

nests are delicate and

disintegrate quickly under

harsh winter weather.

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8 HOMEOWNER Guide to

infertile (non egg-laying) females.Males are not produced untilSeptember.

It is important to know that springweather largely determines if we willhave wasp problems or not in anygiven year. Cold, rainy weatherduring April and May reduces thelikelihood that queens can build anest and collect enough food to feedher immature offspring, while warm,dry weather through June enhancesthe nest success.

SUMMER—WORKERWASPS ABOUNDOnce the first brood of adult workerwasps is produced, they assume

from the queen all tasks of maintaining the nest, foraging forfood, and tending to larvae. The solefunction of the queen becomes egglaying; she remains within the nestfor the rest of the summer. A singleyellowjacket queen can lay tens of thousands of eggs during the season.

 Yellowjacket workers that emergeduring early summer live for 16 to 32days; those emerging in late summerhave a 10- to 20-day lifespan.

Successive generations of workersemerge throughout summer andenlarge the nest. By late August orearly September, a nest initiallyfounded by one overwinteringyellowjacket or bald-faced hornetqueen can consist of hundreds, if notthousands, of living workers.

Paper wasp nests in Idaho aresubstantially smaller, seldomexceeding 100 individuals and oftencomprising fewer than 20 individuals.

FALL—NEW QUEENS DEVELOP;SUMM ER COLONIES DIE

In early fall, workers build specialnest cells where new reproductivemales and queens are produced.When new queens and males emergethey leave the nest and mate. The oldqueen dies shortly afterwards, andthe colony begins to die out. Only thenew fertilized queens survive thewinter; all workers and males diewith the first freezing temperatures.Abandoned, empty nests remain inplace until destroyed by weather.

STING HAZARDS

“Sting” and “bite” commonly—butincorrectly—are used as equivalentterms. Some wasps do bite; they defendthemselves by nipping at attackerswith their jaws. But the painful weltthat results from a wasp attackproperly is called a sting, not a bite.

Stinging insects deliver venom intotheir victims by means of a needle-like apparatus—the sting—locatedat the tip of the abdomen.

Only female insects can sting. This is

because the sting is an egg-layingtube that through the course of evolutionary time became modifiedfor injecting venom. Males cannotsting; they obviously lacked an egg-laying structure that evolutionaryselection could alter into a sting.

Vibrations, shadows, and stings Yellowjackets, bald-faced hornets,and paper wasps are alerted intostinging by vibrations next to theirnests. Dangerous attacks can occurwhen lawn mowers or weed

trimmers unwittingly move overunderground nests of yellowjackets.

Visual disturbances—such as dark,moving silhouettes—around nestopenings also cause stinging attacksby yellowjackets. Yellowjackets aremore readily provoked into stingingduring late summer as natural foods

become scarce and workersaggressively scavenge picnic foodscraps; they also more vigorouslydefend their nest as newreproductive queens and males areproduced.

Multiple stings.Stings of yellowjackets, hornets, and paperwasps are smooth, sharp needlesthat repeatedly can be pushed intothe skin of a victim, allowing eachindividual insect to sting many times.Multiple stings by one individualwasp are are likely especially wheninsects become trapped underclothing against bare skin.

Pain associated with stinging insectscomes not from the sting itself butrather from venom it delivers.Wasp and bee venoms are complex

mixtures of proteins and otherorganic chemicals. Some venomchemicals cause intense pain, otherskill cells and cause swelling, and stillother chemicals spread venombeyond the initial sting site.

Most people react to sting venomswith moderate to intense pain,itching, redness, and swellingimmediately surrounding the stingsite. Usually symptoms go awaywithout treatment in a few hours toseveral days. Sometimes delayed

reactions—such as hot, red swellingof a leg or arm—can last a week.

Multiple simultaneous stings candeliver enough venom to cause toxicinjury even in people not considered“sensitive” to venom. Human deathsfrom mass stinging arephysiologically possible butextremely rare.

Allergic reactions to stingsSystemic (whole-body) allergicreactions to sting venoms occur in1 to 3 percent of the population and

cause about 50 deaths annually in theUnited States. Allergic reactions tostings involve the body’s immuneresponse and require at least twosting episodes: the first sensitizes theperson, and the next sting causes adangerous over-reaction of theperson’s immune system.

Figure 6. Eggs (bottom two cells) and larva(middle cell) are visible within nest cells;capped cells (upper right and lower left)contain wasp pupae. Photo ©DennisSchotzko, University of Idaho

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 Yellowjackets, Bald-Faced Hornets, and Paper Wasps   9

Venoms contain foreign proteins (antigens) thatcause a body to produce its own protectiveproteins (antibodies) called immunoglobulin E,or IgE. After the first sting, the body “remembers”the venom and more quickly produces IgE.Venom antigens bind together with IgEantibodies, causing body tissues to release

histamines into the blood stream.

Histamines cause blood vessels to open wider,capillary walls to become more permeable tofluids (so as to flush the venom away), and lungair passages to constrict. For most people, thereaction to histamines is local swelling anditching around the sting site.

Hypersensitive allergic people release largeamounts of histamine all at once throughout theirentire body, lowering their blood pressure andcausing respiratory distress. Hypersensitization tovenom proteins only requires a single sting. “Hayfever” allergens do not sensitize people to wasp orbee venoms.

Sting venoms of yellowjackets, bald-faced hornets,and paper wasps share enough chemicalsimilarities that some people have allergiccross-reactions to all these species. Venoms of yellowjacket and bald-faced hornets (Vespula andDoli chovespula species) more closely resembleeach other than venoms of paper wasps (Poli stes species). People sensitive to yellowjacketsespecially should be careful around hornets andvice versa.

Honey bee venom differs enough from these

other stinging insects to generate its own IgEallergic reaction, so even hypersensitive peopleusually—but not always—are only allergic tohoney bees or only to yellowjackets, hornets, andpaper wasps.Anyone who ever has suffered asevere allergic reaction to stinging insectsshould consult with his/her physician aboutallergen testing and venom desensitizingimmunotherapy.

 YELLOWJACKETMANAGEMENT STRATEGIES

Even though yellowjackets and their relatives arebeneficial insects, they can pose dangers whennest placement or worker feeding habits put theseinsects in close proximity to people. Reducingsting probability around the home often is amatter of avoiding places where encounters arelikely and eliminating foods that attract theseinsects to backyards.

ADVICE FOR ACCIDENTAL ENCOUNTERS WITH NESTS OFYELLOWJACKETS, BALD-FACED HORNETS, PAPER WASPS

 You and your family can take several common-sense steps to

reduce unintentional contacts with foraging wasps and colony

nests, including:

Walk backw ards/ move slowly. If you have not agitated the

insects into attack, calmly walk backwards from the nest, keepingyour eyes on the nest in case you need to take evasive action.

Move slowly because wasps especially respond to rapidly moving

dark silhouettes.

Flick, don’t swat, don’t crush bodies. Do not swat at flying

workers; they will release air-borne chemicals—called alarm

pheromones—that stimulate a stinging attack from other workers.

If a wasp lands on you, flick it away with your finger. Never crush

the bodies of workers, especially near the nest; crushing also

releases alarm pheromones that induce a mass attack.

If you hear loud buzzing, RUN! But NOT to trees or shrubs. If you

hear loud buzzing or if you already have been stung, run quickly

away from the nest, covering your eyes, nose, and mouth with

your hands or shirt for protection from stings. Take shelter in abuilding or vehicle, or keep running until wasps stop their pursuit.

Agitated yellowjackets may chase you several hundred feet.

Brushy trees or shrubs are not safe shelters because you can be

surrounded and trapped by stinging insects.

FIRST AID FOR STINGS

Always consult your physician about pain medicines and other

first-aid advice; the information presented here does not substi-

tute for professional medical recommendations.

Immediately seek physician or medical emergency

services if the victim

• Is stung around the head and neck or inside the mouth

• Is stung several times

• Already has been stung during the previous week

• Is very young or very old

• Cannot breathe easily, has difficulty swallowing, or feels dizzy

• Develops hives that spread over the body or has a very large

swollen welt

• Has a known hypersensitivity to stings

STING RELIEF STRATEGIES

• Apply ice compresses to reduce swelling and pain.

• Try over-the-counter oral pain medicines and antihistamines,

which may provide relief from pain and itching.

• Wash the sting area with soap to reduce the chances of subsequent infection. Confer with your physician if reddish

streaks develop from the sting; this may be a sign of 

secondary infection.

!

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10 HOMEOWNERGuide to

Colony destruction—a lastresort. Colony destruction is a lastresort for nests in places wherepeople routinely visit. Nests insecluded spots at safe distances fromhuman activities do not necessarilyrequire control action. Those nests

can be left to naturally die out duringfall.

PERSONAL PROTECTION You and your family can take severalcommon-sense steps to reduceunintentional contacts with foragingwasps and colony nests.

•Minimize use of perfumes,colognes, soaps, or other scentedbody lotions when yellowjackets,bald-faced hornets, and paperwasps can be expected; thesescents can be highly attractive to

foraging wasps.

•Wear white or tan clothesratherthan light blues or bright pinks,reds, and oranges; close-fittingshirts and pants are better thanloose-fitting clothes because waspsare less likely to become acci-dentally trapped against the skin.

•Look for foraging workersbefore reaching unseen whenpicking caneberries (raspberries,blackberries), grapes, and treefruits such as apples, peaches, and

pears; these can be highlyattractive to yellowjackets.

• Inspect for nestsbefore doingyard work and home maintenanceduring mid-to-late summer,especially when trimming hedges,mowing dry overgrown weedyareas, weeding rock gardens, orworking around eaves and roofs.

•Wear leather gloves if you mustreach into likely nest sites.

•Teach children to stay away

from (and to tell an adult about)any nests they discover.

•Don’t block the return flightsof foraging workers by standing infront of nests; workers mayinterpret your presence as a threat.

REPELLANTSMint oil and other plant oils are saidto repel yellowjacket workers, but

no research data are available tosupport these claims. At least onecommercial product line of plasticpicnic tablecloths and trash bags(BugAWAY!) impregnated withcitronella, geranium oil, rosemary,and peppermint is marketed as

repelling wasps and other nuisanceinsects.

Commercial mosquito/tick repellants don’t work againststinging insects. Indeed, it ispossible that the scents of someproducts attract yellowjackets andother wasps.

REDUCE ACCESS TO FOODAND WATER To minimize numbers of waspsforaging for sugary liquids, meats,and other resources near people

and picnics:

•Cover serving dishesat outdoorpicnics; clean up spilled drinks andfood scraps; clear away dirty plates.

•Do not leave soft drink cansor beer bottles open andunattended; yellowjackets cancrawl unseen into openedcontainers and sting painfullyaround the mouth.

•Keep lids on trashcansanddumpsters; clean to remove

attractive odors or use disposablecan liners; rinse cans and bottlesbefore placing in outdoor recyclingbins.

•Move food garbageaway frompatios or places where peoplecongregate.

•Don’t leavemoist pet foods outside.

•Control infestationsof aphidsand scale insects that producehoneydew on landscape treesand shrubs.

•Eliminate dripsfrom faucets,sprinklers, and garden hoses,especially during the dry partsof the summer. Puddled waterattracts workers.

•Clean up rotting applesandpeaches that fall from trees; pickcaneberries before they over-ripen.

•Replace late-flowering landscapeplants around decks and patioswith non-flowering ornamentals.

DESTROY EARLY-SEASON AERIALNESTS IN PROBLEM AREASDuring April and May, while nest size

is small and colonies consist of alone founding queen (Figure 7),you can dislodge the aerial nests of yellowjackets, bald-faced hornets,and paper wasps by forcefullyspraying with a garden hose.

 This simple tactic is most effectiveduring cool rainy weather when thequeen cannot quickly start anothernest. Watch the general nest site tosee if the queen returns and tries toconstruct a replacement nest.

 You can safely dislodge early-season

paper wasp nests anytime the queenis foraging off-site and not visible onthe open comb. But only approachthe closed nests of aerialyellowjackets and bald-faced hornetsat night when temperatures are cool;flight activity will be minimal andsting hazard reduced. Stand away ata safe distance.

Never physically knock down, cut-and-bag, or otherwise disturb largenests. The sting hazard is too high.

Subterranean nests. Nests of 

ground-dwelling yellowjackets aremore difficult to physically destroythan above-ground nests. For onething, early-season subterraneannests are hard to find. By the timeyou notice flight activity around nestentrances, colonies probably havegrown to dangerous sizes that defyphysical destruction.

Flooding rarely works.Somepeople recommend floodingunderground nests with a gardenhose or even pouring boiling waterinto nest openings. But unless thenest is located directly below theopening, neither method is effective.Depending on landscape terrain, theactual nest combs may be locatedabove the surface entrance ordistantly located from the entranceand so escape destruction.Covering nest entrances with soilis not effective; trapped waspswill dig new exits.

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 Yellowjackets, Bald-Faced Hornets, and Paper Wasps   11

Never pour kerosene orgasoline into subterranean

nests. This practice poses highhazard of explosive fires plus soilcontamination and groundwaterpollution.

Vacuum removal is a jobfor pros.Nest removal byvacuuming is effective, especially insensitive areas where insecticidescannot be used. But vacuuming istoo hazardous for homeowners.Contact a local professional pestmanagement company for suchservices.

Fall-winter nest removalEliminating aerial or subterraneannests during fall and winter monthshas no impact on populations thenext year because wasps neitheroverwinter in old nests nor re-usethem the following spring. Still, it is agood practice to destroy largeabandoned aerial nests attached tohomes. Old nests can shelterearwigs, carpet beetles, and otherpotential insect pests.

TRAPPING NUISANCE

YELLOWJACKETSUses and limitations Yellowjackets readily can becaptured and killed in a variety of commercial and home-made traps.All traps work on the same principle:yellowjacket workers that scavengefor non-living protein and carbo-hydrate foods are captured inside

containers baited with meats, sugaryfoods, or synthetic chemicals thatsmell like food.

 Yellowjacket traps do not capturepaper wasps. Paper wasps primarilyfeed on living prey and so do not

respond to the same odors asyellowjackets. Traps can temporarilyreduce nuisance problems byattracting yellowjacket workersaway from patios or other backyardareas where people congregate.Four to six traps hung around theperimeter of the yard at least 20 feetaway from people are enough formost home yards. Don’t hang trapson your patio deck or other placeswhere people congregate (Figure 8);traps placed where people gathermay increase sting hazard byattracting even more yellowjacketsthan otherwise would be present.

 Traps capture impressive numbers of yellowjackets but do not eliminatecolonies. Workers commonly forageseveral hundred yards from theirnest and are known to fly 3/4 mile insearch of food. It is not possible toentirely trap-out every worker from

all the nests that potentially occurwithin that range. Theoretically, onecould eliminate yellowjacket nests ina single yard by trapping the initialoverwintering queen during thespring, but this would not stop

problems from nests survivingbeyond an individual yard. Researchshows that overwintering queens arenotoriously unresponsive to traps.

About commercial trapsCommercial traps include bothbaited and unbaited devices as wellas disposable and re-usable designs(Figure 9). Traps baited with a fruity-smelling synthetic attractant namedheptyl butyrate are highly attractiveto our most common species, thewestern yellowjacket, but are lessattractive to the commonyellowjacket and the Germanyellowjacket.

Table 1on page 13 summarizesfeatures of some widely-availablecommercial traps and theirattractants.

Unbaited traps require that you addprotein and carbohydrate foods. Baits

Figure 7. Bald-faced hornet queen beginsspringtime nest construction. Reduce stinghazard by destroying early-season nests inproblem areas while the colony consistssolely of the overwintering queen. Photofrom Ken Gray slide collection, OregonState University

Figure 8. Yellowjacket trap is hung too close to a site frequented by people. This incorrect trapplacement can increase sting threat by drawing wasps to the area. Photo by Edward Bechinski

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12 HOMEOWNER Guide to

like canned, fishy cat food, luncheonmeats, and fruit juices attractyellowjackets, but usually not asmany as synthetic heptyl butyrate.

Natural food baits must be replaced atleast every other day during the heatof summer so they stay moist but donot spoil. Citrus-flavored carbonatedsoft drinks (eg., Mountain Dew,Minute Maid Orange Soda) have

proven highly attractive to Germanyellowjackets in the midwest.

Disposable traps. Disposable trapsreduce sting hazard by eliminatingany need to handle traps containinglive yellowjackets. Re-usable trapsperiodically must be emptied and re-provisioned with food baits orchemical lures. Some re-usable trapsdirectly kill captured insects bydrowning them in soapy water whileother traps restrain livingyellowjackets until they die.

Make your own yellowjackettrap. You can construct your ownyellowjacket traps from large(2-liter) plastic soft drink bottles.

Cut hori zontally through the 

bott le 4 or 5 i nches below the top.

Place natur al food bait s i n a 

small di sposable dri nki ng cup 

located i nsi de the bottom pi ece 

of the bottl e. Inver t the top pi ece 

i nto the lar ger bottom par t so 

that i t makes a fun nel, and then 

secur e the two pi eces wi th tape.

Add an i nch of soapy water 

i n the bottle to drown tr apped 

yellowjackets.

 Yellowjackets respond to food odorsfrom the trap by crawling throughthe opening in the inverted top. Onceinside the cylindrical bottom piece,most yellowjackets will not be ableto find their way back through thefunnel opening.

 You can make another simpletrapby hanging a chunk of fish ormeat by a string an inch or so abovea dishpan filled with soapy water. Yellowjackets feeding on the baitoccasionally bite off more than they

can carry back to the nest so fall intothe water and drown.

 BIOLOGICAL CONTROL—NOT MUCHFOR HOMEOWNERSA surprisingly diverse community of predators, parasitoids, and pathogensprey on yellowjackets and theirrelatives. Unfortunately there is not

much that homeowners can do toenhance the impact of thesenaturally-occurring enemies of yellowjackets. Nor are there anybiological control agents that can bepurchased for mass release.

Commercially available microscopic-

size predatory nematodes potentiallycould be applied as drenches tosubterranean yellowjacket nests. Butbecause it takes days for lethalinfections to develop, applicationwould be limited to yellowjacket

nests where slow-to-develop, partialreductions in colonies areacceptable. California researchshowed some nests recovered evenwhen massive volumes (2 gallons) of nematodes were injected directlyinto nests that had been exposed

by digging away soil.Extreme sting hazard duringapplication further argues againstnematode drenches. Effectivecontrol of aerial nests with nematodesuspensions seems unlikely becausenematodes are aquatic organismsand would quickly dry out and die.

Figure 9. A variety of yellowjacket traps are widely available from retail stores for backyarduse. Photo by author Edward Bechinski

!POISONED FOOD BAITS ARE

HAZARDOUS AND ILLEGAL

It is illegal and highly hazardous

to make poisoned baits for yellow-

 jackets by lacing foods with insec-

ticides. There are no insecticides

that legally may be added to yel-lowjacket food attractants.

Prior to 2002, homeowners legal-

ly could add an insecticide called

Knox-Out 2FM to protein food

baits. Foraging yellowjacket work-

ers 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

about home-made poison baits

readily can be found by Internetsearches, but all violate federal

and state pesticide law.

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 Yellowjackets, Bald-Faced Hornets, and Paper Wasps   13

INSECTICIDESActive nests of yellowjackets, bald-

faced hornets, and paper waspslocated in areas where people

routinely pass may justify insecticidetreatment. Choosing the rightinsecticide can be confusing because

the same insect-killing chemicaltypically is sold under dozens of 

different retail trade names. Here wediscuss products by the name of the

insect-killing active ingredient ratherthan by their many retail trade

names. You always can find thecommon names of active ingredientsby reading the label on the pesticidecontainer. Every pest-killingchemical will be listed on the labelunder the section marked "activeingredients."

We do not recommend insecticideapplication to landscape plantswhere yellowjackets and relatedwasps are foraging for food; we onlyadvise direct treatment of activenests around doors or other places

where sting hazard is high. Treatment of trees, shrubs, and otheryard and garden plants at best onlytemporarily reduces wasp presence.Many repeated applications tolandscape plants would be required.

IMPORTANT. Unless the labelspecifically says the insecticide canbe used for yellowjackets, hornets, orwasps outside around residentialyards and gardens, you have thewrong product. Many products areintended for use only outdoors; never

COMMERCIAL PRODUCT COMPONENTS ATTRACTANT*

Advantage Yellow Jacket Trap for Southern, bucket trap +liquid attractant vinegarEastern, 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 addedby 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

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

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14 HOMEOWNER Guide to

use these inside buildings.

Selection of the best product for out-of-doors nest treatmentaround home landscapes depends on balancing human safetywith control effectiveness.

HUMAN TOXICITY CONSIDERATIONS

Conventional insecticides interfere with the nervoussystem. The insect-killing active ingredients in almost alloff-the-shelf hornet and wasp insecticides are one of two types:pyrethrin and pyrethroids. Pyrethrin is a natural insect-killingchemical extracted from chrysanthemum flowers, whilepyrethroids are human-synthesized compounds similar inchemical structure to natural pyrethrin. Both are widely usedbecause of their quick knock-down, meaning that they rapidlyparalyze the insect.

Both natural pyrethrin and human-synthesized pyrethroids arenerve poisons—they kill by interfering with the nervoussystem—and so pose at least some hazard to humans, pets,and wildlife via accidental exposure.

Virtually all conventional wasp and hornet insecticides forhomeowners are considered by the U.S. EnvironmentalProtection Agency (EPA) as only slightly toxic to people. You can judge the relative toxicity of any pesticide to people bylooking for one of the following special “signal words” printedon the pesticide label:

•CAUTIONdesignates "slightly toxic" products; this is thelowest (least toxic) pesticide category.

•WARNING A few of the more concentrated wasp-killers areclassified by EPA as moderately toxic; these products alwayssay "warning" on the pesticide label and are toxic to people atsmaller doses than pesticides that say Caution on the label

•DANGERNone of the retail wasp insecticides forhomeowners carries the signal word "danger" that designateshighly corrosive pesticides that can permanently injure eyesor burn skin.

Low-risk insecticidesInsect-killing chemicals in two products—the EcoEXEMPTproduct line and Victor Poison-Free Wasp & Hornet Killer—generally are considered by EPA as entirely safe for people. These products contain naturally-occurring plant oils (cloveoil, phenylethyl proprionate, peppermint, rosemary, orwintergreen oils) that are eaten by people in foods and so poseno risks to people.

CONTROL EFFECTIVENESS

CONSIDERATIONSWet vs. dry insecticides The most useful homeowner products for treating outdoornests of yellowjackets, bald-faced hornets, and paper waspsare the ready-to-use aerosol jet sprays and liquid pump-triggersprays that propel insecticidal streams or foaming sprays 20feet or more into nests(Figure 10). These are especially usefulfor treating small aerial nests (golf ball size or smaller) thatcontain relatively few individuals. Treat underground nests of 

SAFETY PRECAUTIONS BEFORE YOU SPRAY

Follow these precautions if you decide to spray a

yellowjacket, bald-faced hornet, or paper wasp nest:

• Inspect the nest. Inspect the colony from a safe

distance (at least 10 feet) during the day so that

you know exactly where the nest entrance of yellowjackets or bald-faced hornets is located

before you spray. DO NOT SPRAY unless you can

see the entrance; otherwise, you will be stung by

insects that escape contact with the killing spray.

• Only spray nests after dark. Wasps are less active

after dark in cool temperatures, and most (but not

all) foraging workers will be present in the nest.

• Do not shine a flashlight directly at the nest. You

may provoke an attack. Do not hold the flashlight

in your hand; agitated wasps will fly to the light.

Illuminate the nest from the side or back with a

light placed on the ground some distance from

where you will be standing.

• Wear heavy clothes and eye protect ion. Protect

yourself from stings by wearing heavy clothing,

a hat, and goggles or other eye protection; some

yellowjackets temporarily blind victims by spraying

venom from their sting into the eyes.

• Take care when spraying around sensitive areas

like vegetable gardens, pet kennels, and windows.

Some wasp and hornet killers specifically prohibit

application to plant foliage. NEVER EAT any

vegetables or fruits that might have accidentally

been sprayed.

• Contract with a professional pest control operatorwhen dealing with:

Large aerial nests of hornets

Late-summer nests of ground-dwelling yellowjackets

German yellowjackets in home wall voids

Nests in attic spaces where potential escape

from stinging attack is limited. These types of 

nests can house dangerous numbers of workers

that pose high sting hazards.

Nests in wall voids present an additional problem:

After colonies have been killed, dead workers,

larvae, and nest materials must be physically

removed from the wall void; otherwise, they

generate an intolerable rotting stench.

!

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 Yellowjackets, Bald-Faced Hornets, and Paper Wasps   15

yellowjackets with ample volumes of liquid insecticides that penetrate andsaturate the entire colony.

Only a few dry-dust insecticides areavailable; these are best suited foryellowjacket nests in wall voids. The

labels of some granular insecticideslist stinging insects as pestscontrolled. Although these productswould kill insects that contact agranule, sprays are better choices.

Knock-down vs. residual killingaction. Some wasp and hornet killerscombine an especially quick-actingbut short-lived pyrethroid insecticide(or natural pyrethrin) with a longer-lasting pyrethroid insecticide. Thefirst ingredient immediately paralyzesthe insect but lasts less than a day

before degrading into inactivechemicals. The second insecticidelasts a few days to several weeks andkills any returning foraging workersthat later return to the nest. Thesecombination products often arelabeled "quick knockdown” and"residual kill."

Short-residual pyrethroid insecticidesfor yellowjackets, bald-faced hornets,and paper wasps include allethrin,bioallethrin, bioresmethrin,phenothrin, resmethrin, sumithrin,and tetramethrin. Again, these namesare the active ingredients that kill theinsects; each active ingredient isavailable in many differentcommercial trade-name products. Bythemselves, these chemicals—as wellas natural pyrethrin—may notprovide satisfactory control; anyworkers that had been foraging awayfrom the nest during pesticideapplication eventually will return andremain agitated around the nest sitefor several days.

Longer-lasting pyrethroid insecticides

for yellowjackets, bald-faced hornets,and paper wasps include beta-cyfluthrin, bifenthrin, cyfluthrin,lamda-cyhalothrin, deltamethrin,permethrin, and tralomethrin. Theseprovide excellent control bythemselves as well as in ready-to-usemixtures with short-residualingredients.

Treating above-ground nestsFor aerial yellowjackets and bald-faced hornets, direct the insecticidestream into the nest entrance. Forpaper wasps, spray across the surfaceof exposed nest comb. Foaming sprayinsecticides are especially effectiveagainst paper wasps.

Spray until nests are soaked. Leavetreated nests in place for a day ortwo; not all workers return to the

nest at night, so any workers foragingaway from the nest during sprayapplication will be killed byinsecticide residues when they returnto the nest. Scrape off dead nestsfrom buildings after two days so thatthey do not discolor exteriorsurfaces.

Treating below-groundyellowjacket nests.Locatingsubterranean nests of soil-nestingyellowjackets requires patience. First,bait the yellowjackets with cat food

or tuna fish, and then watch anindividual wasp as it flies back to itsnest with scavenged food. Foragingyellowjacket workers generally fly ina straight line back to their nest.

 Then go to where you lost sight of theinsect, wait until another flies by, andrepeat the process until you see thenest hole in the ground. Look from a

safe distance for workers flying inand out of the entrance. Don’tapproach too closely because youmay provoke attacks fromyellowjacket workers that guard theentrance. Mark the area and comeback after dark to treat the nest.

Direct the insecticide stream into theopening of subterranean yellowjacketnests. You can plug the entrance holewith soil after treatment to seal

workers inside, but be sure to spraythe soil plug to kill any foragingworkers that later return to the nest.

Treating yellowjacket nests inwall voids.Leave to professionalsboth insecticide application andsubsequent nest removal. But if youdo decide to apply your owntreatments, use aerosols or dusts thatcan be blown into the entire expanseof the nest. After application, plugthe nest opening with fiberglassbuilding insulation; treat the plug

with insecticide to kill any foragingworkers that later return.

Never plug nest entrances as analternative to insecticide application. Trapped workers can chew a newopening through interior walls andemerge in mass into living quarters.

Figure 10. Ready-to-use aerosol jet-sprays and liquid pump-trigger sprays are suited for direct

application to wasp nests. Photo by Edward Bechinski

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Published May 2009 © Universit y of Idaho 2009 $4.00

ABOUT THE AUTHORSEDWARD 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 LifeSciences Barr Entomological Museum; contact him at (208) 885-7079, or [email protected] . LYNDSIE STOLTMAN is graduate researchassistant. HUGH HOMANis University of Idaho professor emeritus of entomology. All are with the Division of Entomology.

PESTICIDES DISCLAIM ERALWAYS read and follow the instructions printed on the pesticide label. The pesticide recommendations in this UI publication do not substitutefor 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 specificallylisted on the label. Store pesticides in their original containers and keep them out of the reach of children, pets, and livestock. Trade names areused to simplify the information; no endorsement or discrimination is intended.

Pesticide ResiduesAny recommendations for use are based on currently available labels for each pesticide listed. If followed carefully, residues should not exceedthe established tolerances. To avoid excessive residues, follow label directions carefully with respect to rate, number of applications, andminimum 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 withthe 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, sexualorientation, age, disability, or status as a disabled veteran or Vietnam-era veteran, as required by state and federal laws.

TO ORDERFor more copies of this publication, or to order BUL 854Homeowner Guide to Bees or BUL 853 Homeowner Guide to Minor Stinging Insects , contact the University of Idaho Collegeof Agricultural and Life Sciences Publications Warehouse at(208) 885-7982, or e-mail [email protected] .

To download these publicat ions for free, go tohttp:/ / info.ag.uidaho.edu:591/ catalog/default.htmandselect insect pollinators.