For Release September 4, 2001

Itís Yellowjacket Season

by Chuck Otte, Geary County Extension Agent

An unfortunate encounter with a yellowjacket nest over the weekend, served as a reminder that we have entered the prime season for these stinging pests. Little understood and often overlooked, yellowjackets are probably our most aggressive stinging insect pest. Their presence in yards and at outdoor gatherings in the late summer and early fall can certainly be enough to spoil anyoneís activity.

First of all, letís clarify some nomenclature and make sure we all have the same names with the same insects. Yellowjackets are a member of the bee and wasp family. Many people call them hornets and they are very similar to the baldfaced hornet that is not very common in Kansas. Yellowjackets are about the same size as, and look very similar to, a common honeybee. They are slightly slimmer and slightly longer than a honeybee. The yellow and black markings on the body are also brighter.

Do not confuse yellowjackets with the wasps that build paper nests in the eaves of buildings. These are Polistes, paper wasps or paper nest wasps. A paper wasp nest is usually fairly easy to see as it is above ground, often in plain sight. Yellowjackets build a paper nest in underground burrows, often in and around logs and old stumps.

Like paper wasps, yellowjackets are very beneficial feeding heavily on caterpillars and other insects. Unfortunately, yellowjackets have a sweet tooth. As summer wanes, so do the number of caterpillars and the yellowjackets go foraging for other food sources. Ultimately they wind up at outdoor gathering of humans where there is food. They not only like sweet liquids, they are also somewhat fond of meat. Unless you unknowingly mow over their nest, you are most likely to meet them where food is involved.

In the late fall, the entire colony dies, except the newly emerged fertile queens. These will gather in number in any suitable winter hibernation areas. In the spring, each queen goes off to start her own colony. For most of the spring and summer, yellowjackets go quietly about their business. The colony is very small to begin with. Initially there is just the queen who is building the nest, laying the egg and feeding the young larva. She has no time to worry about anything else. As the summer progresses she starts to develop a few other workers who can help with all the colony duties.

By mid to late summer, the queen can devote herself to full time egg laying and the size of the colony explodes. By late summer the colony is big enough that there can be full time guards. This is when they become very aggressive at defending their nest. Ouch!

If you find a yellowjacket nest site, you will know it by all the yellowjackets flying around and coming and going from a hole in the ground. Do not attempt to control a nest during the day. Make sure you know for sure where the nest is and then wait until night. Control attempts should be make after dark. Use one of the wasp and hornet killer aerosols, Iíd recommend the foaming kind.

Quietly approach the nest site and apply as much killer into the entrance as you can and then make a hasty retreat. If you must hold a flashlight, cover the lens with red cellophane. After a few days observe if their is still activity at the nest. Multiple treatments over several days may be necessary for total control. Once you are sure the nest is dead, fill the hole with soil to reduce the chance of another colony developing there. And if you know that you are allergic to bee stings, do not attempt to control the nest yourself!


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