ENVIRONMENTAL HEALTH

Yellow jackets

	Picture of a store-bought yellow jacket trap. See link below to learn how to make your own trap.

Most of the yellow jacket activity occurs in the late summer and early fall when colonies reach their highest numbers. Vector Control has been actively conducting a yellow jacket surveillance and control program since 1986. The program includes baiting programs and providing public information on how residents can make their own traps. We respond to hundreds of service calls each year to chemically treat yellow jacket nests in residential areas.

GENERAL INFORMATION

Yellow jackets are social insects that live in nests. Depending on the type of yellow jacket, they build either aerial nests or subterranean nests. Aerial nests are built in trees, utility poles, or on house eaves. Subterranean nests are constructed in rodent burrows, tree cavities, or ground holes. The queen begins a nest in early spring after overwintering. She begins constructing a paper nest about the size of a golf ball and lays eggs in the first cells. When the first group of larvae emerge as adult workers, they take over caring for the young and maintaining the nest. The queen then produces eggs. Over the summer, an individual colony can grow to several thousand workers. In the late summer and early fall, the colony produces a number of queens and drones. These reproductives leave the colony, mate, and the fertilized queens seek out overwintering sites. The drones and workers die shortly after. In the spring the cycle begins again.

Yellow jackets feed mostly on scavenged meat, insects, and other small animals they capture. They are omnivorous, however, and will eat almost anything. The odors of meat, fish, and sweet substances are particularly attractive to the wasps. Yellow jackets are important to our ecosystem. They eat other insects and play a role in pollination when feeding on flower nectar.

The most significant risk of Yellow jackets is from stinging attacks of agitated workers. Unlike bees, Yellow jackets can sting many times. They are especially troublesome in late summer when natural food supplies start to decline and outdoor human activity such as picnicking is high.

MOST COMMON YELLOW JACKETS OF THE TAHOE AREA

Aerial Yellow jacket
(Dolichovespula arenaria)
This yellow jacket is a beneficial organism. Workers prey on flies and caterpillars and rarely scavenge. They build small aerial nests that contain 100 to 700 workers. Nests begin to decline in July to September.

Western Yellow jacket
(Vespula pennsylvanica)
This yellow jacket is a major pest in the Tahoe area. It is primarily a scavenger and is found around garbage cans. Nests are constructed in rodent burrows or in house wall and attics. Nests contain 500 to 5000 workers and start to decline in late September to October.

Prairie Yellow jacket (Vesoyka atropilosa)
This yellow jacket is not a pest. It feeds on live insects, helping to control flies and caterpillars. Nests are found in the ground in open areas like meadows. Nests contain 75 to 400 workers and start to decline in late August to September.

Common Yellow jacket
(Vespula vulgaris)
This yellow jacket can be a pest because adults are attracted to protein or sugar sources. Nests are mostly subterranean (i.e., underground), but can be constructed inside house walls or in aerial locations. Nests are large and contain 500 to 5000 workers. Nests remain active until September and October.

BAITING AND TRAPPING PROGRAMS

The easiest time to control Yellow jackets is in the spring and early summer while the colonies are still small. Baiting worker Yellow jackets can be done by using commercially available containers with Knox-Out 2FM pesticide. The pesticide is mixed with canned mackerel or other bait such as fish based cat food. The bait containers are then hung from a tree limb or other support at least 5 feet above the ground to prevent access by children or pets. Workers carry the pesticide back to the nest and can eliminate the entire colony.

Trapping Yellow jackets is an alternative measure that does not require the use of pesticides. Trapping becomes more effective later in the summer, when yellow jacket workers start aggressively searching for sweets and protein. Yellow jacket traps are available in grocery and hardware stores, or you can make your own.

AVOIDING YELLOW JACKET PROBLEMS

Place all food waste and garbage in cans with tight fitting covers.

Move garbage cans/dumpsters away from eating areas.

Eliminate standing water from dripping outdoor faucets and containers.

Check foods and soda cans before putting them in your mouth.

Localized swelling and pain are typical reaction to the sting by a wasp or bee and they gradually disappear within a few hours. Disinfecting the sting site and applying ice to reduce the swelling is the recommended treatment.

About 1% of the U.S. population may suffer severe allergic reactions. This condition requires immediate medical attention. Symptoms of an allergic reaction or "anaphylaxis" may include difficulty in breathing, dizziness, nausea, and development of hives.