Yellowjackets & Baldfaced Hornets

The term "hornet" is often used to refer to many of the wasps that build large papery nests. The most notable paper wasp is the baldfaced hornet and several species of yellowjackets that are really wasps. In actuality, the only true hornet found in the United States is the European hornet.

Description

Baldfaced hornets are large, black and white, heavy-bodied wasps about ¾-inch

  long. They typically build exposed, mottled grey nests in trees or shrubs. Occasionally, the wasps will build nests under roof overhangs, in attics, crawlspaces and wall voids, or under decks or porches. The nests are constructed of a paper-like material formed from  chewed wood. The nests are often described as "football shaped," but they may exceed a basketball in diameter.

Yellowjackets (commonly called bees) are social wasps the size of houseflies with distinct yellow and black markings and a few hairs. Their nests are also constructed of  paper, though they are tan in color and much smaller than the hornet nest. Common locations for nests are in the ground, in stone walls, in shrubs and trees, in tree trunks and stumps, among piles of stone, wood, or lumber stacked outdoors, and in the walls and eaves of buildings. They are also frequently found around water sources, such as swimming pools or puddles near faucets

Life History

An individual hornet or yellowjacket begins building a nest alone in the spring. Once a queen has produced enough workers to take over nest-building and foraging duties, she remains inside, producing more offspring. The workers expand the nest, forage for food, feed the young, and defend the nest. Like other predatory wasps, their diet consists mainly of other insects, such as flies and bees. Bald-faced hornets will also feed on their yellowjacket relatives. They continue to enlarge the nest until fall when there may be 300-400 hornet, or 600-800 yellowjacket workers. Frequently, it is not until this time that the nest is noticed. In late summer, the colony produces the insects that will mate. The  mated females will serve as the next generation of queens the following spring; the males’main purpose is mating – they cannot sting. Nests are abandoned by wintertime and the future queens seek shelter alone, in protected places under tree bark, in old stumps, or sometimes in attics. The current year's nests are not reused the following spring.

Behavior

Yellowjackets may be late season pests around picnics, trash cans, and hummingbird feeders as they scavenge. The only way to control their presence is to locate and destroy the nest, which is rarely possible. As an alternative, keep all outdoor food and drinks covered when possible. Trash cans should be kept covered or have a flap over the opening. Defensive behavior occurs in response to nest defense, so if a nest is not in the immediate vicinity the likelihood of stings is greatly reduced.

Control

To determine whether control is actually necessary there are two points to remember

1. In spite of their reputations, hornets and yellowjackets are actually beneficial  because they prey on many insects that we consider to be pests, such as caterpillars, and flies. They also are pollinators and serve as food for bears, skunks, birds, and other insects.

2. Unlike honey bees, hornet and yellowjacket colonies die out each year. If a hornet nest is built high in a tree, you may choose to simply wait until the colony dies out in late fall or early winter. The nest will slowly deteriorate from weather or from attack by hungry birds.  If a nest is located where people may be stung or if you (or others) are hypersensitive to bee/wasp stings, then colony destruction may be appropriate. Here are some points to consider as you decide how to approach the problem:

• Control of yellowjackets is best achieved by applying an insecticide dust containing carbaryl directly into the nest opening. Locate and mark the nest opening during the day when yellowjackets are foraging, but wait until dusk to apply the pesticide, when most of the wasps are likely to be at rest inside the nest.

• Baldfaced hornets are easy to control using one of the several insecticidal aerosol products specifically  designed for this purpose. A special nozzle and propellant system spray a thin stream of insecticide up to 20 feet.

• A long-sleeved shirt and long pants may be worn when spraying so the applicator will feel more at  ease.

• Do not wear fragrances such as aftershave lotions or perfumes as these attract wasps.

• Do not hold a lit flashlight or stand near car headlights or other lights. Emerging wasps may be attracted by the light and sting anyone nearby.

• Do not pour gasoline, petroleum, or other hazardous chemical into a nest hole. This is extremely hazardous and environmentally unsound.

• If a nest is disturbed, walk away slowly, keeping your face covered with your hands. Rapid movements result in aggressive responses by yellowjackets.

NOTE: Unlike the honey bee, a yellowjacket does not leave a stinger in its victim so it can sting repeatedly. If the nest is in a wall void or other inaccessible area, consider hiring a pest control company to do the work. If the nest is in a wall it may be desireable to remove it after spraying to avoid attracting carpet beetles that can invade the home and attack garments made wool, silk, or fur. Yellowjacket traps (commercial or otherwise) have not shown to be of any value in reducing a yellowjacket problem.

Adapted from Stephen B. Bambara and Michael Waldvogel, North Carolina Cooperative Extension Service and from the University  of Massachusetts, 2006