NEWS for North Dakotans
Agriculture Communication, North Dakota State University
7 Morrill Hall, Fargo, ND 58105-5665
August 19, 1999
Back-to-school time is here, and many households are no doubt abuzz with anticipation. But around some homes that buzzing sound may be the result of wasps. Fortunately, homeowners have several options when it comes to managing these pesky, stinging insects, says a specialist with the North Dakota State University Extension Service.
"Wasp nests, which actually have been growing all summer, are at their peak size this time of year. Some are probably housing several hundred wasps," says Phil Glogoza, extension entomologist at NDSU. "People suddenly notice the nests because of all the wasp activity."
Many wasp colonies construct hanging nests in trees or shrubs or on building overhangs. But other wasps build lower nests--either underground, nestled among landscape timbers, or underneath a woodpile or the spatial void of a stoop. Glogoza says homeowners often discover ground nests by accident when mowing or gardening, sometimes with painful consequences.
Regardless of whether nests are hanging or at ground level, those that are in out-of-the-way locations pose little threat to humans. Glogoza says wasps generally are not aggressive when foraging for food away from nests. As the season progresses, however, food preferences change and the insects become more aggressive foragers, seeking sweet foods--even if that search means crawling inside a soda can. Wasps are also quite aggressive when defending their nests. For those reasons, wasp nests in or near high-traffic areas can cause problems, and should be removed.
Using insecticides is one option. Glogoza says wasp and hornet sprays are designed with applicator safety in mind. Homeowners can apply the product from a distance of about 20 feet. In addition, the sprays work quickly--knocking down wasps on contact.
"One of the challenges for controlling wasps in hanging nests is that the entrance is at the bottom, so you have to direct the spray toward that opening, without disrupting the wasps," Glogoza explains. "If the wasps are disturbed, continue spraying while slowly backing away from the nest. Rapid movements allow the wasps to focus in on the disturbance."
Similarly, homeowners should direct insecticide spray toward the opening of ground-level wasp nests. But these lower nests also allow the use of insecticide dusts, which homeowners can sprinkle around nest openings.
"All applications of insecticide should be made in the evening hours, at dusk or later," Glogoza continues. "The darkness will offer additional protection for the applicator because the wasps won't be able to see as well, plus the wasps will have returned to the nest for the night, so it's an opportunity to control more members of the colony."
If wasps have built a nest in a hole in a home's foundation, Glogoza says it is critical that the owner make sure all the adult wasps are dead before plugging the hole. He explains, "Any survivors will look for an alternative exit, and that search may bring the insects into the house."
An alternative to using insecticides is trapping. This method is especially effective for controlling wasps in nests that are difficult to access with sprays or when sprays haven't been effective. Glogoza suggests cutting the top off a 1-liter soda bottle at a point below the taper so the "funnel" that results has the same diameter as the bottom of the bottle. Into the bottle, place a bait comprised of one or two cups of sugar-water mixed with about a teaspoon of liquid dish soap.
"The dish soap will disrupt the insects' waxy cuticle and enhance the wetting of their bodies so they will drown," Glogoza explains.
After placing the bait in the bottle, homeowners should push the funnel, inverted, into the bottle until it fits snugly. Inverting the bottle's top makes escape more difficult. When handling the wasp-filled traps, homeowners should wear thick gloves, long-sleeved shirts and pants in case some insects don't drown, Glogoza warns. Placing the dead and surviving insects into heavy plastic garbage bags and then placing the garbage bags in the sun for several hours will finish the job.
Because wasps seek out sweet foods this time of year, the insects have probably already begun foraging around garbage cans and dumpsters. Glogoza says homeowners, businesses and institutions should be especially vigilant about sanitation around these areas so that sources of sweet foods aren't so readily available. Another option for businesses and institutions would be to relocate dumpsters away from areas of human activity until the arrival of freezing temperatures.
"All these nests die out on their own," Glogoza concludes. "Only mated queens will survive, and they may move to another location next year. Having a nest in one location this year does not mean you'll have one there next year. But remember, something attracted the wasps. Inspect the area around the nest this fall and correct any problems you might find, such as holes, or in the case of a woodpile, remove the attraction altogether."
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Source: Phillip Glogoza (701) 231-7581
Editor: Dean Hulse (701) 231-6136