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University
of Rhode Island GreenShare Factsheets
YellowJackets
& Bald-Faced Hornets
Hymenoptera: Vespidae
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, Dolichovespula maculata, and several species of
yellowjackets (Vespula sp.), which are really wasps. In
actuality the only true hornet found in the United States is the
European hornet, Vespa crabro L.
Baldfaced hornets are large, black
and white, heavy-bodied wasps about 3…4 inch (20 mm) 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 martial formed from chewed wood. The nests are
often described as "football shaped", but they may exceed a basketball
in diameter.
Yellowjackets are house fly-sized wasps with distinct yellow
and black markings and a few hairs. Yellowjacket nests are also
constructed of paper, though they are tan in color, much smaller
in size compared to the hornet nest and are usually found in
an underground cavity. Common locations for nests are in lawns,
particularly in sandy exposed areas, as well as at the base of
trees or shrubs. Occasionally, yellowjackets will nest in attics
or walls voids of houses or storage buildings.
An individual hornet or yellow jacket
queen 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, although it has been there for many weeks, already.
In the late summer, the colony produces reproductives--the insects
that will mate. The mated female reproductives will serve as
the next generation of queens in the following spring.The
male's main purpose is mating and 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
attics. The current year's nests are not reused the following
spring.
Yellowjackets, in particular, may be late season pests around
picnics, trash cans and hummingbird feeders as they scavenge.
The only way to control this 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. If the nest is not in the
immediate vicinity the likelihood of stings is greatly reduced.
The first decision to make is whether control is actually
necessary. Two points to remember:
• 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 cabbageworms. They also serve
as food for bears, skunks, birds and other insects. They also
are pollinators.
• 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 is best achieved by applying a pesticide
directly into the nest opening. This can be done at anytime of
the day, but near dusk, most of the wasps are more likely to
be inside the nest. You can use any of the aerosol "Wasp & Hornet" sprays
that propel insecticide in a stream about 10-12 feet. Direct
the spray into the nest opening and then move away from the area
in case any of the wasps emerge from the nest. You may need to
be repeat the treatment on the following evening.
• Long sleeved shirt and long
pants may be worn when spraying to make the applicator feel
more at ease.
• Do not hold a lit flashlight
or stand near car headlights or other lights. Emerging wasps
may be attracted in that direction
and sting anyone nearby.
• Do not pour gasoline, petroleum
or other hazardous chemical down a nest hole. This is extremely
hazardous and environmentally
unsound.
If the nest is in a wall void or other inaccessible area
in your home, you may consider hiring a pest control company
to do the work for you. If the nest is in a wall, it may be desireable
to remove it if convenient 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, 2001
Pesticides
are poisonous! Read and follow all safety precautions on labels.
Handle carefully and store in original containers out of reach
of children, pets or livestock. Dispose of empty containers
immediately, in a safe manner and place. Pesticides should never
be stored with foods or in areas where people eat.
When trade names are used for identification, no product endorsement
is implied, nor is discrimination intended against similar materials.
Be sure that the pesticide you intend to use is registered for
the state of use.
The user of this information assumes all risk for personal injury
or property damage.
For more
information, call the URI CE Gardening and Food Safety Hotline
at 1-800-448-1011 or (401)874-2929 from outside Rhode Island;
Monday-Thursday between 9 am and 2 pm.
University
of Rhode Island Cooperative Extension provides equal program
opportunities.
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