Fact Sheet on Yellowjackets

email: uge1067@arches.uga.edu

GENERAL: Members of the Order Hymenoptera (meaning membrane wing) they are related to bees, other wasps and ants. A large group of wasps often confused with or called hornets (the European hornet is the only true hornet in the U.S.) There are a number of species of yellowjackets in Georgia and the southeastern U.S.: baldfaced 'hornet' (Dolichovespula maculata), European hornet (Vespa crabro), southern yellowjacket (Vespula squamosa), eastern yellowjacket (V. maculifrons), blackjacket (V. consobrina), hybrid yellowjacket (V. flavopilosa) as well as some others. Most yellowjacket workers are small, 1/2 inch long, body stout and slightly wider than head, with yellow and black or white and black markings on the body. They look similar to bees but do not have a hairy body like bees. Some of the species are much larger. They are rapid flyers. Females may sting repeatedly with little provocation, though the baldfaced 'hornet' is not as aggressive as other species. The nests are built underground or they may construct large aerial nests, again this often varies by species, but some will build either. The aerial nest has a globular paper covering that usually encloses multiple combs. The yellowjacket is a beneficial predator; most of its diet consists of other insects many of them pests (e.g. flies, caterpillars, plant bugs, grasshoppers and cicadas). In fruit growing areas, yellowjackets, drawn to downed fruit, can interfere with the harvest by stinging the laborers. Many yellowjacket species are forest dwellers, but some have moved into disturbed areas or urban, including inside walls. Those found frequently in urban areas (southern yellowjacket, eastern yellowjacket and hybrid yellowjacket) ar most likely to be primary pests to humans. They appear to be more aggressive when disturbed, especially in the later part of life cycle in late summer to early fall. This is when they can be nuisance scavengers around picnics and trash receptacles searching out meats, protein rich or sugary foods and drink.

HORNETS: In the U.S. only the European Hornet (Vespa cabro) is a true hornet. Large, 3/4 - 1+ inch long, with yellow and black markings. Another large wasp often called a hornet is the 'Cicada Killer' (Sphecius speciosus), this is not a member of the yellowjackets. It is 1 - 1.5 inches long, black with some yellow markings on the back and abdomen. Cicada killers are solitary nest builders though several females may work together to create a nest of branching tunnels with a few cells at the end of each branch. This large wasp has white or light yellowish markings on face, thorax and part of the abdomen. It is predatory on cicadas, flies and bees that it uses to feed its young. They are not normally aggressive towards humans but their size can be frightening.

BIOLOGY: They are a social insect in large colonies, which they will defend vigorously. The fertilized queen overwinters in a protected area. In spring she digs a cavity in the soil, or starts an aerial nest, with 20 - 45 cells in which she lays eggs. The queen feeds the larvae until they mature to workers and can forage for themselves. In about 30 days the first workers have matured and take over the duties of building the nest and feeding the larvae and the queen. The queen no longer leaves the nest and her primary function becomes that of an egg machine. A colony reaches its peak in late summer. New males and queens mate, males and workers die, and the queen seeks shelter to overwinter. 

STING: In the solitary wasps, such as the 'Cicada Killer', the venom is used to only subdue their prey. Therefore the venom is specialized and usually causes only minimal pain in humans. In the social wasps the venom has developed as a protective mechanism that can cause intense pain and severe reactions in humans. In the worker wasps the stinger is a modified ovipositor (egg-laying device). Unlike the bees, when a wasp stings the stinger is not normally removed from the wasp and left in the wound. That means the wasp can sting multiple times. Reaction to the sting is quite variable from mild pain to extreme pain, itching, trouble breathing, intense swelling, difficulty speaking and confusion or anaphylatic shock; it may be immediate or delayed. If there is any question about the severity of the reaction seek immediate medical assistance. Even if the reaction is only slight the next time it could be life threatening. If you have a known allergy to stings consult with your physician for what you should do. It may be recommended that you carry a 'sting kit' with you for immediate treatment.

CONTROL:
 Avoid stings - move slowly, keep calm when one lands on your skin and carefully brush it off, don't swat or move rapidly. Squashing a yellow jacket releases a chemical alarm that signals other wasps and yellow jackets in the area to attack. Wear light colored clothing, avoid wearing perfume or scented cosmetics, carrying sugary or meat snacks in open containers, walking barefoot and exercise care when gardening. If stung and not allergic, wash the wound and treat with ice, meat tenderizer or commercial sting relief product and don't consume alcohol. Be aware that the next attack could bring a greater reaction. 

Nest removal - Early in the season nests of paper wasps under the eaves can be knocked down; best done in the evening when the wasps aren't active. When the nest is removed the founding wasp will move elsewhere to start a new nest or join an existing one. Do not use a flashlight (unless it has a red lens cover) or car headlights, don't be near or in the light because the wasps may be attracted to it when you disturb the nest. Wear protective clothing.

Proper management of trash/garbage - Reduce access to food (sweets, protein, pet food, and garbage) by proper clean up and covering of trash recepticles. Uncovered trash is an attractive nuisance, discarded soft drink bottles and garbage are almost a guaranteed attraction for yellowjackets and a sting hazard. If yellowjackets become uninvited guests at a picnic, setting aside, away from the picnic area, some food or sweets may draw them away long enough for you to enjoy the picnic.

Chemical control -Because yellowjackets are beneficial predators, chemical control should be confined to the nest site. Apply insecticides at sundown when the whole colony is in or on the nest. Wear protective clothing. Use approved insecticides, applying them directly to the nest. Aerosols for hornets/wasps can spray 20+ feet so you don't need to get too close. Apply quickly and only to the nest or entrance. DO NOT use gas - besides being illegal there is too much danger from fire and contamination of the ground water. Gasoline contamination of the soil is more of a hazard to children and pets than the wasps. If the nest is in a structure, do not plug hole from the outside; they need an escape. Spray an aerosol into the entrance. Next day check for remaining insect activity and repeat application, if required. FOLLOW INSTRUCTIONS ON THE LABEL. 

If you feel the project is too big for you to handle contact a qualified pest control company.

For further control information contact your Extension Service office.

The Audubon Society Field Guide to North American Insects & Spiders, Knopf, NY, 1980.

YELLOWJACKETS AND OTHER SOCIAL WASPS, http://axp.ipm.ucdavis.edu/PMG/PESTNOTES/pn7450.html

CONTROLLING BALD-FACED HORNETS AND YELLOWJACKETS
IN AND AROUND STRUCTURES, http://www.ces.ncsu.edu/depts/ent/notes/Urban/horn-yj.htm

IPM for Yellowjackets and Hornets in Schools, http://www.ifas.ufl.edu/~schoolIPM/tp13.htm

The University of Georgia and Ft. Valley State University, the U.S. Department of Agriculture and counties of the state cooperating. The Cooperative Extension Service offers educational programs, assistance and materials to all people without regard to race, color, national origin, age, sex or disability.

Arnott 08/10/00