Pest description and damage Yellow jackets can be serious pests during late summer months. They become more aggressive and dangerous later in the summer and as summer turns into autumn. A few people (1 to 2 percent) are severely allergic (hypersensitive) to yellow jacket venom, and a sting can be life-threatening.
Yellow jackets are heavy-bodied wasps, black with yellow or white markings. They live in gray, papery nests below ground, suspended above ground, or in the wall voids of houses. Hunting workers search for other insects, carrion, or rotting fruit. The time of year will determine the type of food source the workers will seek out, but generally they are attracted to any meat-based or sugary food. Food is carried back to the nest where it is fed to nest mates. Stings usually occur through accidental contact with the nest or nest entrance. Workers vigorously defend the nest and queen against intruders.
The yellow jacket nest is controlled by a queen whose sole responsibility is to lay eggs. The queen begins a nest in the spring by laying a few eggs and raising these workers to adults. At this point the queen may no longer leave the nest to hunt. Workers provision, expand, and defend the nest all season long. As spring and summer pass, the nest grows as new workers are reared and assume their role. By the end of summer, nests may contain hundreds or even thousands of workers. It is at this time of the year (August-September) that they are most troublesome and dangerous.
By fall the nest also has produced a crop of new queens and male yellow jackets (drones). By the time of first frost, most workers and male wasps have died and only new, fertilized queens remain. New queens leave the nest to find a protected spot to spend the winter. Slow moving yellow jackets seen in the early spring are usually emerging queens. They are commonly found on window sills as they are attracted to the light. They are generally slow and docile, can sting, if stepped on or threatened.
Control may be necessary when yellow jacket nests are near human activity. Treat nests at night with an approved aerosol insecticide. Treating at night is more effective because workers are inside the nest and relatively calm. Use one of the aerosols that claim to propel a stream of insecticide up to 20 feet, so that you can stand a safe distance away and spray directly into the nest opening. These aerosols are referred to as "wasp and hornet spray" or a similar name. Use products specifically labeled for yellow jacket control. Do not pour gasoline, diesel, or paint thinner into nests. This is dangerous, environmentally harmful, and illegal.
In some areas, wasps are collected for their venom, which may be used to produce allergy injections. Local pest control company may offer to locate and remove wasps; usually there is no charge to the consumer for this service. However, only venom from wasps from nests that have not been treated with pesticide may be used.
Nontoxic yellow-jacket traps are available in yard and garden stores. The most effective traps for the western yellow jacket use a synthetic attractant called n-heptyl butyrate to lure workers into a trap from which they cannot escape. Fruit juice or various meats can be used as attractants but are not as effective. Traps can provide some temporary relief for picnics, etc., by drawing workers away from people, but they are ineffective for area-wide nest control even though many yellow jacket workers may be trapped. It is important to place traps away from the house. Some people are allergic to the venom of yellow jackets and others are allergic to bee stings. Both reactions can be life-threatening. If you are particularly sensitive to yellow jacket venom, be cautious in late summer and early fall when the insects are most numerous. Bee stings can occur anytime bees are out of their hives, but are far less common. Honey bee hives should not be destroyed. Local beekeepers will usually remove accessible colonies of bees. County Extension offices and some pest management professionals can provide referrals to local beekeepers.
Other commonly encountered wasp species are mud daubers and paper wasps. Mud daubers build mud tubes, often seen on flat surfaces. Paper wasps build small, open nests suspended vertically from tree branches or roof eaves. Paper wasps are distinguished by their long legs and thin "waists." Both mud daubers and paper wasps are less aggressive and normally will not sting or swarm when away from their nest. If the nests are unsightly, they can be power-washed in the fall, after activity has ceased. In some cases, treating the house eaves with an appropriately labeled pesticide during spring and summer will discourage continued building of nests.