Wasps come in many types and sizes. The ones that are of most concern to people because of their stinging habits are yellowjackets and hornets. Their social organizations range from cooperative fertile female paper wasps to the caste system of yellowjackets, in which there is a single fertile queen and a large population of smaller unmated females. Some social wasps are predators for most or all of the year and provide a great benefit by killing large numbers of plant-feeding insects and nuisance flies; others are exclusively scavengers. Yellow jackets will also forage on foods that people eat, especially sweets and meats.Due to their size and coloration these wasps are often mistaken for bees. Bees are not nearly as aggressive and are valued as major pollinators as well as honey producers.
All wasps will defend their nests, but the Yellow Jackets and hornets are the most aggressive. They can be distinguished from bees by their thin "waists." Bees are thick-waisted. They fold their wings lengthwise when at rest. The yellow jacket colony will remain active for only one summer, after which the queens will fly away to start more colonies. The remaining ones, die at the end of the summer, the nest is not reused.
Wasps become a problem only when they threaten to sting humans. One of the most troublesome of the social wasps is the yellowjacket. Yellowjackets, especially ground- and cavity-nesting ones such as the western yellowjacket, tend to defend their nests vigorously when disturbed. Defensive behavior increases as the season progresses and colony populations become larger while food becomes scarcer. In fall, foraging yellowjackets are primarily scavengers and they start to show up at picnics, barbecues, around garbage cans, at dishes of dog or cat food placed outside, and where ripe or overripe fruit are accessible. At certain times and places, the number of scavenger wasps can be quite large.
IDENTIFICATION AND LIFE CYCLE
Yellowjackets are by far the most troublesome group. Paper wasps are much less defensive and rarely sting humans. They tend to shy away from human activity except when their nests are located near doors, windows, or other high traffic areas.
Nests of both yellowjacket and paper wasps typically are begun in spring by a single queen who overwinters and becomes active when the weather warms. She emerges in late winter/early spring to feed and start a new nest. From spring to midsummer nests are in the growth phase, and the larvae require large amounts of protein. Workers forage mainly for protein at this time (usually in the form of other insects) and for some sugars. By late summer, however, the colonies grow more slowly or cease growth and require large amounts of sugar to maintain the queen and workers. So foraging wasps are particularly interested in sweet things at this time. Normally, yellowjacket and paper wasp colonies only live one season.
Yellowjackets
The term yellowjacket refers to a number of different species of wasps in the genera Vespula and Dolichovespula (family Vespidae). Included in this group of ground-nesting species are the western yellowjacket, Vespula pensylvanica, which is the most commonly encountered species and is sometimes called the "meat bee," and seven other species of Vespula. Vespula vulgaris is common in rotted tree stumps at higher elevations and V. germanica (the German yellowjacket) is becoming more common in many urban areas, where it frequently nests in houses. These wasps tend to be medium sized and black with jagged bands of bright yellow on the abdomen, and have a very short, narrow waist (the area where the thorax attaches to the abdomen).
Nests are commonly built in rodent burrows, but other protected cavities, like voids in walls and ceilings of houses, sometimes are selected as nesting sites. Colonies, which are begun each spring by a single reproductive female, can reach populations of between 1,500 and 15,000 individuals, depending on the species. The wasps build a nest of paper made from fibers scraped from wood mixed with saliva. It is built as multiple tiers of vertical cells, similar to nests of paper wasps, but enclosed by a paper envelope around the outside that usually contains a single entrance hole. If the rodent hole is not spacious enough, yellowjackets will increase the size by moistening the soil and digging. Similar behavior inside a house sometimes leads to a wet patch that develops into a hole in a wall or ceiling.
Immature yellowjackets are white, grublike larvae that become white pupae. The pupae develop adult coloring just before they emerge as adult wasps. Immatures are not normally seen unless the nest is torn open or a sudden loss of adult caretakers leads to an exodus of starving larvae.
Aerial-nesting yellowjackets build paper nests that are attached to the eaves of a building or are hanging from the limb of a tree. The entrance is normally a hole at the bottom of the nest. These aerial nesters are extremely defensive when their nests are disturbed and sometimes bite and/or sting, simultaneously. Wasp stingers have no barbs and can be used repeatedly, especially when the wasp gets inside clothing.
Paper Wasps
Paper wasps such as Polistes fuscatus aurifer, P. apachus, and P. dominulus are large (1-inch long), slender wasps with long legs and a distinct, slender waist. Background colors vary, but most western species tend to be golden brown, or darker, with large patches of yellow or red. Preferring to live in or near orchards or vineyards, they hang their paper nests in protected areas, such as under eaves, in attics, or under tree branches or vines. Each nest hangs like an open umbrella from a pedicel (stalk) and has open cells that can be seen from beneath the nest. White, legless, grublike larvae sometimes can be seen from below. Paper wasp nests rarely exceed the size of an outstretched hand and populations vary between 15 to 200 individuals. Most species are relatively unaggressive, but they can be a problem when they nest over doorways or in other areas of human activity, such as fruit trees.
Mud Daubers
Mud daubers are black and yellow, thread-waisted, solitary wasps that build a hard mud nest, usually on ceilings and walls, attended by a single female wasp. They are not social wasps but may be confused with them. They do not defend their nests and rarely sting. During winter, you can safely remove the nests without spraying.
INJURY OR DAMAGE
Concern about yellowjackets is based on their persistent, pugnacious behavior around food sources and their aggressive colony defense. Stinging behavior is usually encountered at nesting sites, but scavenging yellowjackets sometimes will sting if someone tries to swat them away from a potential food source. When scavenging at picnics or other outdoor meals, wasps will crawl into soda cans and cause stings on the lips, or inside the mouth or throat.
Responses to wasp stings vary from only short-term, intense sensations to substantial swelling and tenderness, some itching, or life-threatening allergic responses. Of specific concern is a condition that results from multiple-sting encounters, sometimes unfamiliar to attending health professionals, that is induced by the volume of foreign protein injected and the tissue damage caused by destructive enzymes in wasp venom. Red blood cells and other tissues in the body become damaged; tissue debris and other breakdown products are carried to the kidneys, to be eliminated from the body. Too much debris and waste products can cause blockages in the kidneys, resulting in renal insufficiency or renal failure. Patients in this condition require medical intervention, even dialysis.
MANAGEMENT
Most social wasps provide an extremely beneficial service by eliminating large numbers of other pest insects through predation and should be protected and encouraged to nest in areas of little human or animal activity. Although many animals prey on social wasps (including birds, reptiles, amphibians, skunks, bears, raccoons, spiders, preying mantids, and bald-faced hornets), none provides satisfactory biological control in home situations.
The best way to prevent unpleasant encounters with social wasps is to avoid them. If you know where they are, try not to go near their nesting places. Wasps can become very defensive when their nest is disturbed. Be on the lookout for nests when outdoors. Wasps that are flying directly in and out of a single location are probably flying to and from their nest.
Scavenging wasps will not usually become a problem if there is no food around to attract them. When nuisance wasps are present in the outdoor environment, keep foods (including pet food) and drinks covered or inside the house and keep garbage in tightly sealed garbage cans. Once food is discovered by wasps, they will continue to hunt around that location long after the source has been removed.
If wasp nests must be eliminated, it is easiest and safest to call for professional help.
If a rapid solution to a severe yellowjacket problem is essential, seek the assistance of a professional pest control operator who can use microencapsulated baits to control these pests. Do-it-yourself options include trapping wasps in a baited trap designed for that purpose, early-season removal of nests, or spraying the nest or nesting site with an insecticide labeled for that use.
Trapping Wasps
Trapping wasps is an ongoing effort that needs to be initiated in spring and continued into summer and fall, especially when the yellowjacket population was large the previous year. In spring there is a 30- to 45-day period when new queens first emerge before they build nests.
Trapping queens during this period has the potential to provide an overall reduction in the yellowjacket population for the season. The more traps put out in spring on an area-wide basis to trap queens, the greater the likelihood of reducing nests later in the summer. Usually one trap per acre is adequate in spring for depletion trapping of queens; in fall, more traps may be necessary to trap scavenging wasps, depending on the size of the population. There are two types of wasp traps: lure and water traps.
Lure Traps.Lure traps are available for purchase at many retail stores that sell pest control supplies and are easiest to use. They work best as queen traps in late winter and spring. In summer and fall they may assist in reducing localized foraging workers, but they do not eliminate large populations. Lure traps contain a chemical that attracts yellowjackets into the traps, but common lures such as heptyl butyrate are not equally attractive to all species.
Proteins such as lunchmeat can be added as an attractant and are believed to improve catches.
During spring, baited lure traps should have the chemical bait changed every 6 to 8 weeks. In summer, change the bait every 2 to 4 weeks; change bait more frequently when temperatures are high. Meats must be replaced more frequently because yellowjackets are not attracted to rotting meat. Also, periodically check the trap to remove trapped yellowjackets and make sure workers are still attracted to the trap.
Water Traps. Water traps are generally homemade and consist of a 5-gallon bucket, string, and protein bait (turkey ham, fish, or liver works well; do not use cat food because it may repel the yellowjackets after a few days). The bucket is filled with soapy water and the protein bait is suspended 1 to 2 inches above the water. (The use of a wide mesh screen over the bucket will help prevent other animals from reaching and consuming the bait.) After the yellowjacket removes the protein, it flies down and becomes trapped in the water and drowns. Like the lure trap, these traps also work best as queen traps in late winter to early spring. In summer and fall they may assist in reducing localized foraging workers but usually not to acceptable levels. Place them away from patio or picnic areas so wasps aren't attracted to your food as well.
Discouraging or Eliminating NestsEarly in the season, knocking down newly started paper wasp nests will simply cause the founding female to go elsewhere to start again or to join a neighboring nest as a worker. As there is little activity around wasp nests when they are first starting, they are very hard to find. Wasps are more likely to be noticed later after nests and populations grow.
Nest removal for controlling subterranean or cavity-dwelling yellowjackets is not practical because the nests are underground or otherwise inaccessible.
Nest SpraysAerosol formulations of insecticides on the market labeled for use on wasp and hornet nests can be effective against both yellowjackets and paper wasps, but they must be used with extreme caution. Wasps will attack applicators when sensing a poison applied to their nests, and even the freeze-type products are not guaranteed to stop all wasps that come flying out. It is prudent to wear protective clothing that covers the whole body, including gloves and a veil over the face. In addition, you need to wear protective eyewear and other clothing to protect yourself from pesticide hazards. Wasps are most likely to be in the nest at night. But even after dark and using formulations that shoot an insecticide stream up to 20 feet, stinging incidents are likely. Underground nests can be quite a distance from the visible entrance and the spray may not get back far enough to hit the wasps. Partially intoxicated, agitated wasps are likely to be encountered at some distance from the nest entrance, even on the day following an insecticidal treatment. Hiring a pest control professional will reduce risks to you and your family. Add this page to your list of favorite web sites.
SOCIAL WASPS
YellowjacketsDescription: 12-17.5 mm in length; head, thorax, and abdomen black and yellow or white; body fairly stout; wings smoky.
Life cycle: In the spring the fertilized female builds a small nest and begins laying eggs. She tends to the resulting larvae until the first brood matures into female workers, which rear consequent larvae and extend the nest. As many as several thousand workers may be produced in a colony in one season. Males develop from unfertilized eggs toward the end of summer and mate. At the onset of cold weather all the wasps, including the old queen, die except young mated females which over winter among leaf litter or in soil.
Habitat: They usually nest underground in an old rodent burrow, beneath a landscape timber, or in a rock wall or wall of a building, or at ground level in fallen logs and tree stumps. In urban settings they can also be found under stairs, in fence posts, brick walls and discarded mattresses, carpets, boxes, etc. The German yellowjackets are often found nesting in wall voids, attics, or crawl spaces. Whether in the ground or within a wall void, the yellowjackets nests are made of wood pulp and saliva used to form layers of cells encased in a protective paper covering.
Food: Adults feed on nectar and other insects, larvae are provided with pre-chewed insects and pieces of meat. Adults can become pests around outdoor eating areas and garbage cans because they are always scavenging for food scrapes. They also forage for sources of sugars or other carbohydrates, such as beer, fruit, and sweet beverages. As the new queens are produced in the colony in late summer, they demand sugars from the workers, which the forage aggressively for sources of sugar. They are very aggressive and will sting repeatedly at the least provocation.
Bald-faced Hornets
Description: 16-20mm in length; body stout with black and ivory white markings on the face, thorax, abdomen, and first antennal segment; wings smoky. These are not true hornets but are members of the wasp family.
Life cycle: In the spring females construct small pendant nests with a few cells and begin laying eggs. The first brood matures into female workers, which feed the larvae several times a day and continue nest expansion. In the late summer males develop out of unfertilized eggs and mate. Only young mated females survive the winter to start the cycle again in the spring.
Habitat: Gardens, parkland, meadows, and forest edges. Nests are constructed out of wood pulp and saliva and attached to branches in the open. They consist of many layers of cells encased in protective paper with an opening at the bottom. The nest resembles a large inverted teardrop shaped ball, and can contain thousands of wasps, which are extremely aggressive when disturbed.
Food: Adults consume fruit, nectar and other insects; larvae are fed pre-chewed insects.
MORE INFORMATION ON BALDFACED HORNETS: The Bald faced hornet (Dolichovespula maculata) is sometimes called the white-faced hornet, but is actually a yellowjacket. It's easy to spot since it's our only black and white yellow jacket. Its nest is a gray "paper" envelope with several layers of combs inside. A mature nest can be bigger than a basketball, but pear-shaped, with the larger end at the top and an entrance hole near the bottom. A single, over-wintering queen begins building the nest in the spring. She lays eggs and tends the first batch of larvae that develop into workers. These workers tend new larvae and expand the nest throughout the summer. A mature colony can have several hundred workers by the end of the summer. In fall, workers die and next year's queens find over-wintering sites. Baldfaced hornets are beneficial, capturing insects (often including other yellowjackets) to feed to their larvae. Though larger than other yellowjackets, Baldfaced hornets are generally more docile. But they can become aggressive and will sting when their nest is disturbed or threatened. A Baldfaced nest is usually constructed high in a tree. In these cases the nest is best left alone. In fact, Baldfaced hornet nests are often first noticed in fall when leaves drop, exposing the nest. By this time the hornets are dead or dying, and the nest will not be reused. Occasionally you will find a Baldfaced nest built on the side of a building, in low shrubbery, or even in an attic or shed. Nests in these sites will probably need to be eliminated.
Solitary Wasps
The family Sphecidae is made up of a large variety of solitary hunting wasps. There are about 1200 species in North America, many of which are common. They feed upon spiders or insects such as aphids, caterpillars and cicadas. The hunting wasps feed this prey to their young, which develop in separate nests in the ground, natural openings or in cell constructed out of mud, like the mud daubers. The hunting wasps do not live in colonies but often may nest together in large numbers at a site. The solitary hunting wasps often are rather fearsome looking but rarely sting and do so only if handled. Most of these wasps are beneficial predators of pest species and do not require control.
Black-and-yellow Mud Dauber
Description: 25-30 mm in length; long cylindrical one segmented "waist" (pedicel) between thorax and abdomen; body black with large yellow area on prothorax; yellow pattern on thorax, pedicel, and 1st segment of abdomen; legs mostly yellow; wings brown-black.
Life cycle: Solitary female builds a nest out of moist mud containing several parallel cell rows. A paralyzed spider is stuffed into each cell and one egg deposited on each spider. The female then closes the cell opening with mud. Hatching larvae slowly consume the spiders after which they pupate inside the cell. Males are rarely seen before midsummer and feed on nectar.
Habitat: Rock faces, under rocks, overhanging roofs, attics and other structures.
Food: Adults feed on nectar, larvae feed on provided spiders.
CONTROL
Unless wasps, hornets, and yellow jackets become a threat we urge you to leave them alone. They play an important role in the ecological balance of your backyard, neighborhood and local community.
Yellowjackets and hornets are outside the nest during the daylight hours. Nearly the entire colony is in the nest during the evening and nighttime hours, although some workers may be stranded away from the nest and will not return until morning. Control measures for hornets and yellowjackets should be attempted during the nighttime hours when the whole colony is in or on the nest.
There are many insecticides labeled for controlling wasps, when applied into or onto the nest. The difficulty involves making the treatment without being stung. If applications must be made during the day, protective equipment such as boots, heavy coveralls, veiled headwear, and heavy gloves should be worn. This equipment should be carefully secured in such a fashion that wasps can not slip under cuffs or other areas of the clothing. Use plenty of masking tape wrapped around the bottoms of pant legs and sleeves and around the collar.
An aerosol spray of one of the many fast-acting wasp killer aerosols will quickly kill most workers present in ariel nests.
The most difficult problems in wasp control are generally those that involve large aerial nests of yellowjackets or bald-faced hornets and ground or structural nests of yellowjackets. Control of aerial nests of hornets and yellowjackets should be attempted only while wearing a full set of protective equipment. Direct the spray into the hole at the bottom of the nest, being careful not to break open the side of the nest. Within a few hours, or certainly by the next day, all the colony members should be killed by this initial application.
Control of ground-nesting yellowjacket nests is best done at night for safety reasons. The nest entrance should be located during the daytime and marked in some way for easy and precise location in the evening. When the nest is approached at night, it is a good idea to have the available light (spotlight or flashlight) set and focused on the nest from a distance, off to the side. Do not hold it in your hand, because it may attract attacking workers. It is safest to wear protective clothing. Approach the nest slowly and carefully.
The quickest and surest way to kill the colony is with insecticide dust. The only product registered for wasp control in The United States is sold only to certified applicators. Dust will travel deeper into the void, in the ground or wall, than will an aerosol wasp killer.
Mud daubers are not aggressive about defending nests under construction. However, protective clothing should be worn. A residual insecticide liquid or dust application to the mud nests and the surfaces in the immediate area will provide effective control. Then, scrape away and remove the nests, if possible.
If you are allergic or hypersensitive to wasp or bee stings you should not attempt to control these insects and should call a professional pest control company. Or if you do not have the proper equipment call a professional pest control company.
Wasp Traps (Make your own traps)
Keeps yellow jackets away from desired area( however will not kill out the entire colony). Safe. Non toxic. Traps place and maintained in the early spring will help to severely reduce the yellow jacket population in the fall. For every female you capture in the early spring, that will eliminate a yellow jacket nest of 500 to 5,000. Fruit juice or meat are lures that work well. Placement of the trap:
1. Place traps away from all human activity.
2. Hang traps 2-4 feet above ground.
3. Yellow Jacket Traps should be baited and placed either early morning or late evening when the yellow jackets are least likely to be active.
4. Place traps in sunny areas when temperature is below 80-85 degrees F. Place traps in shaded area when temperature is above 85 degrees F.
5. If Yellow Jacket catch is low, relocate the trap. Leave trap in an area for at least 2 days.
Maintenance:
1. Before emptying traps, make sure all yellow jackets are dead.
2. If live yellow jackets are present, they must be killed before opening the trap by : a. Pouring soapy water into the trap or b. Placing entire trap in a freezer for 48 hours.
.3. Trap should be emptied and cleaned every 3-4 weeks. Traps must be kept clean.
Hints: Only the fertilized female yellow jacket survives over winter. All males die during the winter. This may be the reason they are so aggressive in the early fall and know this is their last "Hoorah".
When fertilized females emerge from hibernation in early spring, she needs protein to nurse her young offspring. To start with she is a single mom doing it all until she can raise some workers.
Outdoor events wasp control
Late-summer and fall yellowjackets are much tougher to eliminate. Yellowjackets can be foraging from dozens of hidden nests in the area, each nest containing thousands of workers, and they may come from nests 1,000 ft. or more away.
Yellowjackets change their feeding behavior in late summer. No longer the beneficial, insect-eating predators they were in the spring and summer, they have become freeloaders — scavenging on fruits, ice cream, beer and soft drinks. They are aggressive and willing to sting.
Yellowjacket management at parks, festivals, football games and similar outdoor events can be the worst job of all. The sheer numbers of yellowjackets can be intimidating. And there is so much sweet, rich food to attract them.
IPM now prevents trouble laterYou can often avoid severe yellowjacket problems in the fall by eliminating workers and nests in late spring and summer, when yellowjacket workers are few and their nests are still small.
Monitoring is the key. Monitoring — documented and systematic inspections at regular intervals — is a critical part of IPM, and essential for yellowjacket management.
Check around a property frequently. Look for yellowjacket nests or foraging yellowjackets. Install a few yellowjacket traps (how many will depend on the area) and check them at each visit. Check the traps weekly or biweekly in July and August, if possible, because this is the critical period to head off fall problems.
If the traps begin catching yellowjackets, place enough additional traps that they become control tools, reducing the numbers of yellowjacket workers. See if you can track foraging workers back to their nests. Mark all the nests you find, and come back at night to destroy the nests when most of the yellowjackets are inside.
Do not quit when you find a yellowjacket nest; there may be many more. Keep monitoring and keep looking.
Using traps for control:Trapping will not eliminate yellowjackets. But aggressive trapping — using lots and lots of traps — will significantly reduce the number of fall foraging yellowjackets and the risk of stings.
You can choose from many different commercial yellowjacket traps. Some are disposable; most come with bait or bait enhancers. Some drown the trapped yellowjackets; others hold them until they die from heat or until you kill them.
Not all yellowjacket species respond equally well to all traps or all baits. Different colonies of the same species will even exhibit preference differences. The time of the year also affects bait choice.
Experiment with different baits and traps to find the most suitable one for a particular site. Place traps according to the manufacturer’s directions. Do not stint; you need lots of traps to get effective population reduction.
Sanitation’s roleForaging yellowjackets are attracted to areas where food is readily available.
Their numbers and the risk of stings can be reduced, sometimes quite significantly, simply by changing trash and food management practices.
Although yellowjackets are not the first pest to come to mind when thinking IPM, they are actually very susceptible to the IPM approach. Fall yellowjacket problems at outdoor events, in fact, can only be successfully managed through IPM. Insecticides alone will have little effect.
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