Brochures
Yellowjackets
 Most people know and fear the yellow-and-black striped yellowjacket wasps that are common, uninvited guests to late summer picnics. Their stings are painful and for those people allergic to insect venom, they are dangerous. Many people confuse bees, which are fuzzy and only feed on flower nectar, with wasps, which have shiny bodies and are predators. What most people don't realize is that yellowjackets capture enormous numbers of flies, caterpillars and other insects to feed their young. They have been seen bringing in more than 225 flies an hour to a single nest; one study found that over a three day period, just two wasps collected 20 grams of imported cabbageworms. It is usually only in late summer, when their populations are at their peak and wasps are attracted to plants with ripening fruit or aphid honeydew deposits on the leaves that most conflicts arise between humans and yellowjackets. Although they are touchy defenders of their nests, most stings are a result of accidentally trapping or pinching a wasp.
You can avoid being stung by following a few rules:
- Remove all outdoor food sources attractive to wasps. Feed pets indoors and keep garbage
cans tightly covered and wash cans regularly to remove spilled food. Bury fallen
fruit and table scraps deep in compost piles and don't compost meat scraps or
bones.
- Watch where you sit or step (don't go barefoot!). Be especially careful to look before
reaching into berry bushes or picking fruit. Thirsty wasps are attracted to
moisture so be cautious when sitting on or handling wet beach towels.
- Never swat at a yellowjacket hovering around you—it is a good way to get stung.
Instead, quietly move away or let the wasp leave of her own accord. The only
exception to this is if you have accidentally disturbed a nest and hear wild
buzzing. In this case protect your face with your hands and RUN!
- Pick fruit in the early morning or evening while it is cool and most wasps are still in their nests.
To reduce yellowjacket problems at picnics and barbeques:
- Minimize the length of time food is available by keeping it tightly covered until just
before it is to be eaten. Clear away scraps and dirty plates as soon as the meal
is over.
- Serve sweet or alcoholic drinks in covered cups with drinking straws through the lids
so wasps can't get inside and then sting you in the mouth as you drink. When
drinking out of a can, keep the opening covered with your thumb between sips.
- Set up baited yellowjacket traps around the edge of the picnic area or on the end of
the table to attract wasps away from the food to capture them. Small disposable
cardboard traps or reusable ones made of wood and metal screen are sold at
garden centers. They work by attracting wasps to bait placed under an inverted
funnel. When the wasps have had their fill and instinctively fly upwards toward
the light at the end of the funnel, they are trapped in an enclosed chamber
above. In early and mid-summer, 1-2 traps should be enough for most picnics. In
August and early September, however, six or more traps might be necessary. For
much of the season, the best baits are Spam, ham, fish, cat food or meat scraps.
Later in the summer, when wasps need less protein because they aren't rearing
their young, sweet baits such as jam, honey or rotting fruit are often more
attractive. When the picnic is over, sink the traps in a bucket of soapy water
to kill the wasps. Make very sure they are dead before cleaning out reusable
traps.
Removing Wasp Nests
Although the number of yellowjackets in late summer invariably prompts many concerned inquiries on how to control them, usually there is little that can be done. The wasps will all die in a matter of weeks as fall approaches. Even if a nearby nest is discovered late in the summer, eliminating it may not have the desired effect because wasps can fly in from up to a mile away. It is never advisable to put out poison baits because children and pets may get into them and because other, beneficial, insects may take the bait and be killed. It is also a terrible idea to pour gas or kerosene into an underground wasp nest where it poisons the soil.
If yellowjackets do build a nest in a location likely to cause problems with people or livestock, the best time to remove it is early in the season, while it is still small. This is a job for a very careful person or a professional pest control service. Chemical wasp sprays are available, but if you use them, consider very carefully where the stream of pesticide that misses the nest will land. Always use such products according to direction on the label. Remove an exposed nest that has been sprayed as soon as the wasps are dead. Wear rubber gloves and dispose of the nest to prevent birds from eating the poisoned larvae left inside.
To remove a hanging wasp nest without using chemicals:
First, it is a good idea to get a helper. To be safe, both of you should wear protective clothing from head to foot. Although a beekeeper's suit with hat and veil is ideal, you can assemble a similar suit for the occasion from heavy coveralls, a hat with a wide brim and a length of fine screening. Wear boots with your pants cuffs pulled outside the boot tops and seal the cuffs around the boot top with rubber bands so that wasps can't get up your legs. Wear gloves and pull your sleeve cuffs over the tops of the gloves and seal them the same way. Drape the screening over the hat (the brim should keep it away from your face) and tie it around the neck, over the collar of the coveralls. Make sure there are no openings around the collar or base of the veil. You should wear another layer of clothing underneath the overalls because wasp stingers are long enough to reach through one layer of cloth.
To remove the nest, approach in the evening or at night when the wasps are all home and less active because it is cool. Have your helper hold open a large, heavy bag or a box with a tight lid under the nest while you cut the attaching stem of the nest as quickly as possible using a long handled pruning hook, or other tool. When the nest is in the bag or box, close it immediately and seal shut. Kill the wasps inside by putting the whole package in a deep freeze for 24 hr. or by directing a wasp spray into the package through a small hole for several minutes. Don't neglect this last step because wasps can eventually chew their way out of almost anything.
Wasp nests in walls:
Wearing suitable protection as above, spray pyrethrins (fast-acting, short-lived compounds extracted from pyrethrum daisies) into the opening of the nest at night. Repeat applications nightly until no more wasps are seen leaving the hole. Never block up the opening as wasps can chew through wood or follow wiring to the interior of the house. In the fall, when the nest is definitely vacant, caulk or repair the crack to prevent recolonization next year.
Underground wasp nests:
This is a job better left to a pest control operator, who can dig and vacuum out the nest, however, you can apply pyrethrins sprays as above or pour several gallons of boiling water into the nest. Wear protective clothing as described and be extremely careful not scald yourself with the boiling water.
Lifecycle
In spring, the mated queen wasp crawls out of her overwintering shelter, fills herself on flower nectar and insects and then builds a nest in a hole in the ground, inside a wall cavity, or hanging from a branch or the eaves of a building. She chews up plant fibers and weathered wood to make a grey papery pulp for the first egg cells. The queen rears this  first brood herself, foraging for food and feeding the larvae. In about a month these larvae become adult worker-daughters and take over cleaning, building and feeding chores for the next generation. The wasp population grows and the nest expands all season as the workers add new layers of cells. In late summer the queen stops laying eggs and the last of the brood matures. Among the last generation in late summer are both queens and males that develop in special cells. When they emerge, they mate and the queen crawls away into a hiding place under bark, in an old stump or under litter to spend the winter. The workers and males all die before winter, the nest falls apart and is not reused next year.
1992
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