AUBURN, Ala. – 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.
Dr. Xing Ping Hu, an Alabama Extension entomologist, said hornets and yellow jackets are the most common wasp groups.
With the exception of honeybees, all female and worker wasps and bees can sting repeatedly. The chance of a person becoming sensitive to the venom increases with every occasional sting.
“Be cautious of small areas that are bare of vegetation because they could be ground nests of yellow jackets,” Hu said. “By fall, yellow jackets and hornets have reach their maximum size of family members. Fall is also the period when they are most active.”
“Hornets usually construct exposed nests in the branches of trees and shrubs or on recessed structures,” Hu said. “They also construct nests in cavities.”
Most yellow jacket species nest in the ground, but some nest in buildings, in tree cavities or structural voids.
A new colony 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 are often overlooked. By fall, however, nests reach their maximum size and typically contain 300 to 120,000 developmental cells, depending on the species and environmental conditions.
“In South Alabama, some species maintain large perennial colonies,” Hu said. “In these colonies, multiple queens rule the colony, which are tended by thousands of workers and contain millions of cells.”
Most of the summer, yellow jackets are predators and feed on other insects. In the fall, their diets change to preferable sugary concoctions. You will see them feeding on rotting fruit, tree sap, human beverages, sweet food, fruit juice and other sweet substances. They also labor long hours to collect enough food to feed and maintain the colony through the winter.
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.
Hu said air carries dust formulations deep into cavities and voids of the 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.
Alabama Extension has a publication, Yellow Jackets, Wasps, and Hornets, that provides further information. For more information, contact your county Extension office.