Friday, August 21, 2009

Be Aware of Yellowjackets

Yellowjacket workers are ½ inches in length, with black with yellow markings on the head, thorax and abdomen. The yellowjackets use their chewing mouthparts to construct carton nests out of chewed vegetable fiber. Nests are usually underground, but occasionally they can be found in wall voids and indoors. Their nests are usually spherical and consist of a number of round combs that are attached to each other and then surrounded by a layered outer covering.
The colony begins with a single queen that has survived the winter. The queen is very large and more orangish in color. In the spring, the queen's ovaries develop and she finds a nesting site. She constructs a nest of 20 to 45 cells and produces eggs that hatch into larvae. The queen feeds the larvae for about 30 days or until the larvae pupate and develop into adults. Later in the summer, workers construct larger reproductive cells in which male and female wasps are produced.
Yellowjackets are considered beneficial since they feed developing larvae arthropod prey. However when their nests are disturbed, defending worker wasps can sting multiple times. Also, foraging worker wasps may be a nuisance at picnics and other outdoor events.

Some Control Options:
One strategy is to hang traps in sunny locations in areas of nesting sites. Liquid insecticides can also be used to kill yellowjackets. Also insecticidal dusts can be used and are sometimes preferred since the workers attempting to use the nest opening will track dust and contaminate brood and other colony members.
All must be used with extreme caution, since wasps will attack when sensing an insecticide applied to their nests. Wear protective clothing that covers the whole body, including gloves and a veil over the face. Hiring a pest management professional is sometimes needed to reduce risks to you and your family.

Southern yellowjackets, Vespula squamosa (Drury) (Hymenoptera: Vespidae), at nest entrance. Photo by G. McIlveen, Jr.

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