Fall is the peak season for yellow jackets and hornets in Alabama. Many people encounter and experience painful stings from these wasps during outdoor activities.
Yellow jackets are black-and-yellow social wasps. Hornets and yellow jackets are the most common wasp groups, says Dr. Xing Ping Hu, an entomologist with the Alabama Cooperative Extension System.
“By fall, yellow jackets and hornets reach maximum size of family members and peak period in activities. Hornets usually construct exposed nests in the branches of trees and shrubs or on recessed structures. They also construct nests in cavities,” added Hu. Most yellow jacket species nest in the ground but some nest in buildings, in tree cavities or structural voids.
The cycle begins with a few mated overwintered females who start new nests in early spring and become foundress queens. The new nests may contain a dozen developmental cells, remain relatively calm and often overlooked.
By fall, annual nests reach maximum size and typically contain 300 to 120,000 developmental cells, depending on the species and environmental conditions. “Some species maintain large perennial colonies in South Alabama. Multiple queens rule the colonies which are tended by thousands of workers and contain millions of cells,” said Dr. Hu.
Most of the summer, yellow jackets are predators and feed on other insects. In the fall, their diets change to preferable sugary concoctions. They are attracted to rotting fruit and tree sap, human beverages, sweet food, fruit juice and the like. They also labor long hours to collect enough food to feed and maintain the colony through the winter.
Humans should be aware of stinging wasps when in fruit orchards, flower beds, picnic areas, outdoor restaurant seating and at backyard barbecues.
Managing Yellow Jackets
“The most useful tool for managing yellow jackets is a dust applicator,” Hu said. Hand dusters and air dusters are the more common applicators. A pest control professional wearing protective garments should operate dust applicators.
Dr. Hu says air carries dust formulations deep into cavities and voids of wasp nests. The dust particles remain on the concealed surfaces awaiting contact with foraging yellow jackets, which, in turn, contaminate other nest mates.
Using wettable powder insecticides in surface-treating yellow jacket nests can accelerate the colony-elimination process. It permits sameday nest removal.
Apply aerosol and mist insecticides, such as pyrethirins, and other botanical extracts to nest cavities after dark when nest members are in the treatment zone.
Although it is necessary to close off multiple entry points for wasps from structural voids to living and work spaces, homeowners should never caulk close an exterior entrance to an active yellow jacket nest in a structure. This action alarms the trapped wasps and causes them to seek alternative escape routes to the outdoors.
Except for honeybees, all female and worker wasps and bees can sting repeatedly. With occasional stings comes the likelihood of increased sensitivity to venom.
“Be cautious of small areas bare of vegetation because they could be ground nests of yellow jackets,” added Dr. Hu.
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