Yellowjacket wasps often become a nuisance in late summer and autumn when they nest around homes, buildings and areas where people live, work and play. Although these wasps are considered beneficial because they feed on flies and caterpillars, they can build up in large populations and scavenge for meat and liquid sweets at picnics, county fairs, sports events, outside restaurants, bakeries and other locations. Their boldness and stinging ability cause concern.

Identification

A typical yellowjacket worker is about l/2 inch long, short and blocky, with black and yellow bands on the abdomen and a yellow face. Sometimes, they are confused with honey bees. Queens are about 50 percent larger than the workers.

Life Cycle and Habits

Most yellowjackets nest in the ground and along foundations in colonies up to 6,000. These three yellowjackets are established statewide:

• Bald-faced homes nests are usually aerial structures attached to trees, buildings, weeds, power poles or rock overhangs.

• Southern yellowjacket nests are usually subterranean or in walls of buildings
• Eastern yellowjacket nests are usually subterranean, in creekbanks, stumps, walls or other cavities in structures, cars or boats (Fig 1).

Yellowjackets are social wasps that live in colonies containing workers, queens and males. Workers construct and defend the nest and collect food. Fertile queens lay eggs throughout the summer. Males die shortly after mating. Nests are gray, papery and soccer or football shaped. Nests are abandoned in the fall. Workers die after a few frosts or a good freeze, and the mated queen overwinters in protected outside locations or in structures.

Treatment of Stings

After being stung, immediately apply a poultice of a meat tenderizer to the wound. If the sting is not deep, this will break down the components of the sting fluid, reducing pain. Also, a commercial preparation, such as a Sting Kill swab, can be used. Antihistamine ointments and tablets taken orally appear effective in reducing reactions to stings. Highly sensitive people should consult their physician about a desensitization procedure and carry a medical kit such as Ana-Kit. These kits contain antihistamines and aqueous epinephrine (administered by injection). They may also contain a bronchodilator material (inhaler).

Control Measures

PREVENTION: Yellowjackets can sting repeatedly and are attracted to rapid movement; therefore, remain calm and stationary. Never swing or strike at a wasp. If one gets in the car, carefully pull over, open the windows and doors slowly, allowing the wasp to escape.

Sanitation is important. In the autumn, yellowjackets often get protein and carbohydrates from human foods. Cover food, clean up spills and keep refuse in tight-sealing trash containers. Pick up and dispose of ripe fruit and vegetables in the area.

Avoid the use of heavy scented soaps, shampoos, perfumes, colognes, aftershaves and cosmetics. Avoid shiny buckles and jewelry. Cover exposed skin and wear gray, white or tan instead of bright colors.

Yellowjackets can be killed with traps consisting of a pan of water with detergent added to eliminate surface tension. Place the pan under a piece of meat or fish suspended on a string, an inch or two above the water's surface. Yellowjacket workers feed and become heavy, falling into the water. It is not unusual to fill a dishpan with drowned yellowjackets in one afternoon. However, trapping even large numbers often fails to reduce populations to acceptable levels. Some commercial baits containing diazinon (Knox Out) will kill yellowjackets.

INSECTICIDES: Chemical control should be considered as a last resort because worker populations are gone after a hard freeze or several frosts. If you decide to use an insecticide, wear protective clothing (with bee veil, if possible) to cover the body, and do the treatment after dark when most wasps are inside the nest. It is best to work in pairs with one holding the flashlight (red cellophane over lens) and the other applying the insecticide. For ground nests, pour about one quart of 2 1/4 percent carbaryl (Sevin) solution into the nest opening or openings and cover with a shovel of moist soil. Resmethrin (Synthrin, Incinerate), or propoxur (Baygon) sprays are also effective.

Concealed nests are the most difficult to control. Yellowjackets may nest inside a wall a considerable distance from the entrance. Spraying the opening may have little effect. Never plug up the entrance hole to the outside as yellowjackets have been known to eat through plaster board and enter homes when confined. If the nest cannot be located, after dark, tape a small paper lunch bag over the entrance. Put three to four tablespoons of 5 percent carbaryl (Sevin) dust in the bag and make a dime-sized opening in the end. As the yellowjackets pass through the bag, they carry the insecticide into the nest, killing the workers and the queen. Leave the bag on for a few days until no more wasps are seen. Bendicarb (Ficam D) dust is also effective

Be prepared for yellowjackets by having on hand a pressurized aerosol containing synergized pyrethrins and rapidly volatizing organic solvent, such as Whitmire Wasp Freeze.

Additional insecticide formulations that only the certified pest control operator may use include bendicarb (Ficam W), bendicarb plus pyrethrins (Ficam Plus), and pyrethrins (Pyrenone).