Wasps and Yellow Jackets - June 21, 2006
Jeff Schalau, County Director, Associate Agent, Agriculture & Natural Resources
Arizona Cooperative Extension, Yavapai County
Wasps and yellow jackets are beneficial insects. They feed their young on insects that would otherwise damage crops and ornamental plants in your garden. They can also feed on house fly and blow fly larva. Wasps and yellow jackets become aggressive when their nests are approached or disturbed. This is often when people and animals are stung. While these stings are painful (and life threatening to those that are allergic), these insects should be respected and tolerated under most conditions.
Wasps can either be social (living in a colony) or solitary and are differentiated from yellow jackets and hornets by their slender body and long legs. The most common wasp found in urban and suburban areas is the paper wasp. These insects often build their nests under eaves of structures or in other protected locations. The benefits of wasps usually outweigh potential for harm unless a nest is in a high traffic area such as a doorway or outdoor living area. When approached, paper wasps leave the nest and dive bomb intruders occasionally inflicting painful stings. Both wasps and yellow jackets can sting multiple times.
Yellow jackets forage for a broad range of foods, but they often come into conflict with humans when they are attracted to meat, carbonated beverages, juices, desserts, and other food items. They are commonly a nuisance to outdoor diners during the summer months. Yellow jackets will often enter cans of sweetened carbonated drinks. Unknowing drinkers can find an agitated yellow jacket in their mouth. This can become serious if an allergic individual is stung in the mouth or throat. Yellow jackets also gather around uncovered trash receptacles where they can freely gather food.
The western yellow jacket usually nests in the ground using an abandoned burrow, but can occasionally nest in crawlspaces or wall voids. Underground nests can be disturbed unknowingly by hikers and outdoor workers. When this happens, they emerge from the nest and attack the intruder. Underground, the nest is a papery structure that provides a home and breeding area for the queen and contains combs where young are raised.
Social wasps and yellow jackets use a nest for one year although paper wasps may construct a new nest adjacent to an old one. Solitary wasps are not usually a danger. This is important when considering the need for control. Keeping in mind that these insects are beneficial, where the nest is not posing an immediate threat to people or pets, it can be left for the season and removed during the winter months.
Sometimes, control becomes necessary. Exposed nest can be sprayed with aerosol products labeled for this use. They are usually synthetic pyrethroids that have a quick knockdown effect. These spray insecticides are marketed especially for wasps and yellow jackets and produce a spray stream of up to 20 feet. The nest should be sprayed thoroughly in the early morning or late evening. Do not use a flashlight as they will follow the light beam to its source. Do not remove the nest before all wasps are dead. This can take a day or so because some wasps may forage overnight. Those returning will be killed when they come in contact with the sprayed nest.
A similar approach can be used on ground nesting yellow jackets. Spray the entrance in the early morning or evening and leave it alone for a few days. There are some aerosol products that produce foam on contact. Iíve found these products to work well on yellow jacket nests.
Traps can be used when large numbers of yellow jackets are pestering outdoor diners. Commercial traps are available in reusable and disposable designs. I have always used a homemade trap made from a five gallon bucket, a stick, a piece of wire, and a fish or meat scrap. A piece of fish or meat is tied to the wire and suspended from the stick over the bucket above a few inches of soapy water. The yellow jackets eat so much that they cannot fly very well. When they take off, they hit the side of the bucket and fall into the soapy water where they sink to the bottom. Some yellow jackets will still pester diners but they eventually find the bucket.
Finally, remember that these insects are beneficial and control is not always necessary. The University of Arizona Cooperative Extension has publications and information on gardening and pest control. If you have other gardening questions, call the Master Gardener line in the Cottonwood office at 646-9113 ext. 14 or E-mail us at firstname.lastname@example.org and be sure to include your address and phone number. Find past Backyard Gardener columns or submit column ideas at the Backyard Gardener web site: http://cals.arizona.edu/yavapai/anr/hort/byg/.
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Last Updated: June 15, 2006
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