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Growing Green: Stinging Insects Put a Damper on Summer Fun

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While enjoying these glory days of summer, keep an eye out for one of the season’s most notorious party crashers – stinging wasps and bees. These insects build nests underground, in trees, shrubs, overhangs, eaves, utility poles, tires, houses, sheds and other structures. People often mistakenly call all stinging insects “bees”, however, wasps and bees look and behave differently. It is important to distinguish between these insects because different methods may be necessary to control them if they become a nuisance.

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Wasps have a slender body with a narrow waist, and appear smoothed-skinned and shiny. Yellowjackets, baldfaced hornets, and paper wasps are the most common types seen in Minnesota. In contrast, bees are full-bodied and very hairy.

Wasps and bees sting to defend themselves.Wasps and bumblebees can sting more than once because they are able to pull out their stinger without injury to themselves. Honey bees have barbs on their stinger which remain hooked in the skin. The stinger is torn out of the abdomen as the bee attempts to fly away. As a result, the bee soon dies. If you are stung by a honey bee, scratch out the stinger  with a credit card or your fingernail as soon as possible. Do not try to pull out the stinger between two fingers. Doing so only forces more venom into your skin, causing greater irritation.

The best time of the day to control wasp nests is at night, when they are less active. Wasps have difficulty flying at temperatures below 50° F. If you see a wasp nest, but it doesn’t interfere with your activities, leave it alone.  If left undisturbed, the wasps won't bother you. However, nests that are near human activity can be problematic. If you are concerned, you should get rid of  the nest. Apply a ready-to-use aerosol “wasp and hornet spray” into the entrance of the nest about an hour after dark following label directions. If no activity is observed the next day, the nest has been successfully exterminated. If live wasps are still observed, repeat the treatment at three-day intervals until they are all dead.

When yellowjackets are found nesting in the ground, try pouring a liquid soap and water solution into the entrance. If that doesn't work, apply an insecticide into the nest opening. Be sure you use a product that is labeled for use in lawns or soil. Dusts are more effective than liquid insecticides because liquids do not always reach the nest. Cover the nest entrance with soil when the wasps have been exterminated.

The most challenging nests to control are those that are concealed behind walls or in attics. Often, the only evidence of the nest is wasps flying back and forth through a crack or hole in the home. Aerosol insecticides usually do not work very well against hidden nests. The best method is to apply a small amount of insecticidal dust.

Honeybees and bumlebees play an important role in our environment.  Honey bees are responsible for more than 80% of the pollination required by most fruits and vegetables as well as many flowering plants. Bumblebees are also important pollinators of native prairie plants. If these insects really present a problem; if they have moved into a high traffic area or someone in your family has a severe bee allergy, nest eradication may be warranted. Treat with the same insecticides and methods as described for exposed or concealed wasp nests.

For more information about wasps and bees, visit: www1.extension.umn.edu/garden/insects/find/wasp-and-bee-control/

Robin Trott is a Horticulture Educator with University of Minnesota Extension.

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Robin Trott

Robin Trott is a Horticulture Educator with University of Minnesota Extension.

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