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What's the buzz? Yellowjackets in the schoolyard
In late summer and fall, yellowjackets can cause problems around schools. Although they are often beneficial, preying on other insects, they can sting many times if provoked. In this way, yellowjackets differ from bees, which sting only once. Yellowjackets will aggressively defend their nest if it is disturbed.
How to Identify Them
Yellowjackets are relatively short and stout wasps, and they hold their legs close to their bodies. They have either black and yellow or black and white stripes. They are fast fliers and are more aggressive than other wasps. They make nests, enclosed with a papery envelope, in the ground, hanging from trees or eaves, and sometimes in wall voids.
How They Live
To begin a nest, the queen yellowjacket builds a small comb of chewed wood. She lays eggs in the cells and tends the larvae herself when the eggs hatch. Once the larvae develop into adults, those workers expand the nest into many layers. A colony seldom grows larger than 15,000 workers for a single queen, although multiple queens can support a larger population in perennial colonies. The colony produces new queens and males in the late summer or early fall. After mating, the queen finds a sheltered place to spend the winter, and the workers die (except in perennial colonies). The nest eventually disintegrates. Early in the warm season, yellowjacket numbers are low enough that they are not a problem. When they reach their peak in late summer or early fall, they become pests. Garbage cans, lunch counters and playgrounds attract yellowjackets looking for protein and carbohydrate sources. Usually, yellowjackets that are foraging for food won?t sting unless they are physically threatened. But they will aggressively defend their nest if they feel it is in danger. If someone steps on an underground nest opening or disturbs a nest in a shrub or building, yellowjackets are likely to sting many times. Sometimes coming near a nest that has been previously disturbed is enough to spark an attack. Vibrations, such as those from a lawnmower, can disturb undergound nests as well.
How to Prevent Attacks
The goal of a yellowjacket management program is to reduce human encounters with them. Eliminating them with chemicals should be used only as a last resort and only in a situation involving frequent stings because yellowjackets are beneficial predators of pest insects. Physical controls such as trapping and the removal of food sources are the most productive method of managing yellowjackets. Look for nests in the ground, under eaves and in wall voids. Wasps often build ground nests under shrubs, logs, piles of rocks and other protected sites. Entrances sometimes have bare earth around them. To get a good idea of the nest locations and entrances, watch for wasps to enter and leave. Garbage containers on school grounds should have tight-fitting lids and be emptied frequently. Periodically, lids and containers need to be cleaned of food wastes. When this isn't done, the garbage site attracts yellowjackets in search of food. This can cause students to fear getting close enough to the cans to put their garbage inside. Any food spilled or left outside the cans then attracts more yellowjackets, and the cycle continues. Dumpsters should be cleaned often with a strong stream of water. Repair windows and screens and caulk holes in siding to prevent yellowjackets from establishing nests inside a building. Inspecting the building once a month will turn up new nests before they become large enough to present a real problem. Nest removal and trapping can significantly reduce yellowjacket populations as well. A nest can be destroyed with pesticides or through vacuuming. Do not forget that multiple stings can occur when the nest is disturbed. It is best to have a pest control operator with experience in stinging insects remove nests.
For additional information about the management of yellowjackets and the prevention and treatment of stings, please visit the University of Florida's School IPM Web site (http://schoolipm.ifas.ufl.edu). Click on Technical Information - Pests, then select "IPM for Yellowjackets and Hornets in Schools."
Edited by: Angela Brammer, University of Florida
