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Fall brings out the aggression in yellow jackets

Posted: September 19, 2015 - 11:19pm

During this time of the year, yellow jackets become more aggressive.

The main reason for this aggressive behavior is that the population of the nest is at its highest during the fall, which increases the demand for food.

The many colony members also protect that food source in the nest. Anyone intruder into the nest area will be stung. Yellow jackets are actually wasps with distinct yellow and black markings. Like other wasps, they make a paper nest. The nest can usually be found underground in stump holes or under shrubs. Occasionally, yellow jackets will nest in attics, old cars, storage buildings or in walls of homes and buildings.

A yellow jacket colony begins in April or May when the overwintered queen emerges. The queen is the only member of the colony that can survive through the winter. She finds a nest site and builds a small paper nest. She lays several eggs that hatch and mature to adult workers. Once the queen has produced enough workers to take over nest-building and foraging duties, she stays inside the nest producing more offspring. The workers assume all tasks of nest expansion including foraging for food, defending the colony entrance, and feeding the queen and larvae. By late summer, a yellow jacket nest will have about 800 workers. This is the time of the year that most people find the nest, because of the large number of workers entering and leaving. This is the time of the year when the next generations of queens are produced. The colony produces reproductive cells that produce new queens and males. They eventually leave the nest for mating flights. Inseminated queens seek a protected place such as a brush pile, a hollow tree, or a building to spend the winter. Males that have successfully mated quickly die. The current nest will be abandoned by wintertime. Usually, the nest is not used again by yellow jackets.

There are several things that you can do to help protect yourself from yellow jackets. Keeping in mind that the yellow jackets are often searching for food during this time of year, cover all food and drinks while eating outside. Also, garbage cans attract yellow jackets. Keep lids on garbage cans whenever possible. If there are a large number of wasps circling an area, the entrance to the nest can be located by following the yellow jackets flight pattern. If the nest is located in an area that does not pose harm to people, leave the nest alone.

Yellow jackets are beneficial insects. They prey on many insects that we consider pests, especially caterpillars. If the nest is in an area that endangers people, tit will need to be treated with an insecticide.

The best control is to apply an insecticide directly into the nest opening. Visit your local hardware store or garden center and purchase a product labeled for yellow jacket control. Follow all label directions. Insecticides should be applied late evening or at night when all adult workers are inside the nest. The nest entrance should be identified and marked during daytime. A quick knockdown insecticide spray, containing pyrethrin, is preferred because yellow jackets will fly out to defend the colony when disturbed. Yellow jackets are attracted to light; therefore, do not use a flashlight while applying an insecticide to the nest. Check the nest entrance the next day for activity and reapply again if necessary. If daytime control is necessary, wear protective gear including a hat, veil, coveralls, and gloves because returning workers will likely attempt to defend the colony.

As you are out in the yard this time of year, remember to keep an eye out for yellow jackets. Remember, they are most aggressive when protecting their nest.

Tripp Williams, Columbia County’s agriculture and natural resource extension agent, can be reached at (706) 541-4011, ortrippj@uga.edu.

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