Christian County Extension Office
Managing Wasps and Hornets
Wasp stings are a serious health threat to humans and animals. Many people in the United States die each year from allergic reactions to the venom of these insects. Paper wasps, hornets and yellowjackets are more dangerous and unpredictable than honeybees. Workers foraging away from the nest are seldom aggressive, but nests should be eliminated with great care and in a specific manner. "Folk" remedies such as dousing nests with gasoline or a garden hose seldom work and can result in multiple stings.
Each of these insects constructs nests of a paper-like material containing finely chewed wood fragments and salivary secretions. Paper wasps typically build their umbrella-shaped nests in protected locations, such as under eaves, gutters and ledges or in attics and outbuildings. Nests also may be located behind shutters, or inside exterior light fixtures, gas grills and mailboxes. Most paper wasps are brownish or rust-colored, although one increasingly common variety, the European paper wasp, has yellow and black markings much like a yellowjacket. Paper wasps have a “waist” that is very thin, however, which distinguishes them from hornets and yellowjackets.
Paper wasps are not very aggressive, but stings can occur when homeowners inadvertently disturb nests that are hidden. If the nest is accessible, it can be eliminated rather easily with a wasp and hornet spray sold at most retail stores. One advantage of these formulations is that they can be sprayed as far as 20 feet. Although it’s best to treat all wasp nests at night, paper wasps can be eliminated during the daytime provided you do not stand directly below the nest during treatment. Since most wasp aerosol sprays cause insects to drop instantly, standing directly under a nest increases the risk of being stung. After treatment, wait a day to ensure that the colony is destroyed; then scrape or knock down the nest.
Hornets are far more difficult and dangerous to control than paper wasps. Their nests resemble a large, gray, bloated football, which typically is attached to a tree, bush or side of a building. Oftentimes the nest is concealed among branches, especially in densely canopied trees such as Bradford pear. Hornet nests may contain thousands of wasps that are extremely aggressive when disturbed.
When controlling hornet nests apply an aerosol-type wasp and hornet spray or dust formulation (e.g., Sevin, Drione, DeltaDust) directly into the nest opening. Hornet nests generally have a single opening, usually toward the bottom, where the wasps enter and exit. It is crucial that the paper envelope of the nest not be broken during treatment or the irritated wasps will scatter in all directions, causing even greater problems. Like yellowjackets, hornet nests should be treated at night when most insects are within the nest and less active. A full wasp suit, sealed at the wrists, ankles and collar, is recommended. Following treatment, wait at least 2-3 days before removing the nest to ensure that all of the wasps are killed. If hornets continue to be seen, the application may need to be repeated. The nests often are located out of reach and elimination is best accomplished by a professional pest control firm.
Yellowjackets are probably the most dangerous stinging insects in the United States. They tend to be unpredictable and usually sting if the nest is disturbed. Yellowjacket nests are often located underground in old animal burrows or beneath rocks or landscape timbers. They also build nests in walls, attics, crawlspaces, and behind exterior siding of buildings.
If the nest can be located, it often can be eliminated by applying an aerosol-type wasp and hornet spray into the opening. Insecticide dust formulations containing Sevin, DeltaDust, or Drione, are especially effective but require a hand duster to dispense several puffs of the dust into the nest opening. In lieu of a commercial duster, a workable alternative is to use a dry, empty liquid detergent bottle filled with an inch or so of dust. A few pebbles or marbles added to the bottom prevents the dust from caking, and the bottle should be shaken before dispensing. (Remember to dispose of the bottle after use, or store it away from children and pets). Insecticide dust blown into the opening penetrates farther than sprays, and the workers transport it throughout the nest.
Ideally, treatment should be performed at night, when most of the yellowjackets are in the nest and less active. Pinpoint the nest opening during the daytime, so you will remember where to direct your treatment after dark. Approach the nest slowly and do not shine the beam of your flashlight directly into the nest entrance as this may startle the wasps and cause them to fly toward the light. Instead, cast the beam to the side to illuminate the nest indirectly. If possible, place the light on the ground rather than in your hand.
When contemplating extermination of a yellowjacket or hornet nest, be fully aware that you are entering a danger zone. There is no pest control scenario more frightening than a ‘blown’ wasp or hornet treatment. It is often prudent to hire a professional, especially when access to the nest requires a ladder or is difficult. If the nest is located away from frequently used areas, another option is to wait and do nothing. In Kentucky, wasp, hornet and yellowjacket colonies die off naturally after the weather turns cold, and the paper nest disintegrates over the winter months.
For more information on gardening, you can call the Christian County Cooperative Extension Service at 270-886-6328. With this week’s garden tip, I’m Kelly Jackson.
Educational programs of Kentucky Cooperative Extension serve all people regardless of race, color, age, sex, religion, disability, or national origin.
UNIVERSITY OF KENTUCKY, KENTUCKY STATE UNIVERSITY, U.S. DEPARTMENT OF AGRICULTURE, AND KENTUCKY COUNTIES, COOPERATING