Beware of the Wasp: Tips for Keeping Bees at Bay

If you’ve ever been harassed by an annoying yellow jacket while weeding your garden, you’re not alone.

As temperatures climb with each passing day of spring, gardeners usually face a growing battle with ornery wasps and hornets and those pesky little yellow jackets.

Dr. Xing Ping Hu, an Alabama Cooperative Extension System entomologist, says while all species of bees are usually relatively harmless, there are ways to avoid them.

Yellow jackets, wasps, hornets and honey bees are all usually referred to as "bees" by the general public, Hu says.

"They are actually often beneficial, preying on other insects," she says. "But they are stingers, thus they pose a potential health threat to Alabamians. While no species will attack a human except in defense of their colonies, if they are provoked or disturbed they can become aggressive. They may respond by releasing hundreds of defending workers which are all capable of delivering several stings. Honey bees are an exception; they can sting only once."

The stings can be painful, causing itching, pain and localized swelling. The stings can be fatal for those allergic to the venom, Hu says.

"Wasp venom contains factors that release histamine, which dissolves red blood cells," she says. "Only female wasps can sting. The males do not because their stinger is actually a modified ovipositor. All stinging wasps build a nest from which they conduct many of their activities, especially rearing their young."

If you kill one wasp in the spring, you actually kill a colony that may produce more than a thousand wasps later in the season, she says.

"Sudden cold snaps in the spring can sharply reduce wasp population for the rest of the year," Hu says. "Since only queens survive the winter, the number of wasps is low every year in the spring. During spring, the single queens emerge from hibernation and begin to build nests and produce offspring. The number of wasps goes up in the summer and peaks in the fall each year."

Wasps are usually relatively harmless in the spring, but their defensive behavior increases throughout the season.

"There are usually few incidents of stings in the spring, but their colonies become larger during the season, and they become more defensive as food becomes more and more scarce. In the fall they show up at picnics, barbecues, around garbage cans, at dishes of pet food placed outdoors, and on ripe or overripe fruits."

There are two types of wasp nests: aerial nests and in-ground nests.

Aerial nests may be attached to trees, twigs, rocks or human structures such as eaves and ledges on the sides of buildings or homes.

"A nest may house hundreds or thousands of individual wasps," Hu says. "The best way to prevent unpleasant encounters with wasps is to avoid them. If wasp nests are considered a nuisance or are posing a latent threat, have them professionally removed. Otherwise, the nests should be left alone because they are beneficial insects."

Other wasp management methods include removing old nests and scraping the point of attachment.

"Caulk openings in attics, window frames and around wall penetrations to keep over-wintering females out of unused rooms and spaces," she says. "Wasps are usually not a problem if there is no food around to attract them, so keep food and drinks covered and keep garbage in tightly sealed cans. If you anticipate a big wasp problem this year, start trapping wasps this spring and continue this summer and fall."

Many yellow jacket and wasp traps are available, she says, but they should be considered a secondary strategy to be used only if the wasp population is high.

"Some people use a canister-type vacuum cleaner to vacuum the nest," Hu says. "If you use a vacuum cleaner, avoid cutting into the nest. That provides more than one exit for the angry wasps. The vacuum bag should be immediately plugged and the wasps killed by freezing or some other means. If all other methods are deemed unfeasible, chemical means can be attempted. For this approach, remember to wear a protective suit and take precautions. Nest spraying should be attempted only after dark, when all foragers are back in the nest."

Call your local Extension agent for more information on which sprays are best, Hu says.

"Most aerosol and dust products provide rapid knockdown," she says. "Do not use gasoline to burn ground-dwelling wasps. When attempting to rid your home or yard of wasps, have first-aid supplies available, and plan for emergency care for sting victims who are dangerously sensitive."

SOURCE: Dr. Xing Ping Hu, (xhu@aces.edu), Extension Entomologist, Alabama Cooperative Extension System, (334) 844-6392