Extension Educator, Horticulture
Autumn means picnics and outdoor festivals. Unfortunately fall activities may include some unwanted guests – yellowjackets. Yellowjackets are a member of the bee and wasp family. The yellowjacket's ability to sting repeatedly makes them a considerable health threat. Yellowjackets alone are responsible for about one half of all human insect stings.
Yellowjackets are about 3/4 inch long with brightly colored yellow and black stripes and very little hair. Yellowjackets may be confused with hover flies, which have been abundant this year. Some people call hover flies "sweat bees" for their tendency to land on your skin for a drink of sweat. As their name implies, hover flies literally hover in one spot like a hummingbird. They have short antennae as opposed to the long black antennae of yellowjackets. Hover flies are good guys and cannot sting. Their larvae are voracious predators of aphids, thrips and small caterpillars.
Yellowjackets live in nests in old rodent burrows, woodpiles, brush piles or hollow trees. In late summer a nest may contain several thousand yellowjackets. Be very careful when doing yard work this time of year that requires moving woodpiles or brush piles. New nests are started each spring.
Yellowjackets are attracted to areas with sweet food such as picnic areas and ice-cream stands. Open cans of garbage, unclean garbage cans or areas of rotting fruit are major yellowjacket attractants. Since yellowjackets often crawl into soda cans unnoticed, people are frequently stung on the lips.
Ways to avoid yellowjackets include not wearing strong perfumes or brightly colored clothing. Don't go barefoot. Outdoors use drinking cups with lids.
Avoid swatting or squishing yellowjackets. I know for some this may require a great deal of self-control. Squashing a yellowjacket releases a chemical that signals other wasps in the area to attack. The worst reaction is the chaotic sequence of flailing arms and swatting of the offending yellowjacket.
Yellowjackets will not bite or sting a person unless they or their nests are agitated, stepped on or heaven forbid sat on. However they may land on your skin to take a drink of sweat or inspect a smell. Just be patient and they will fly away. If you can't be that patient, very gently brush them off with a piece of paper with slow deliberate movements. The same method should be used if a yellowjacket makes its way into your car.
Yellowjacket traps are marginally useful to reduce the population. However, keeping garbage cans clean and covered, keeping outdoor food areas clean and removing rotting fruit is still necessary to keep yellowjackets in check. Once yellowjackets figure out a place for food, they will keep coming back.
A yellowjacket nest around the home may require additional control measures. Remember bees and wasps are important pollinators so indiscriminant destruction of their nests should be avoided.
Yellowjackets are active during the day so control measures are best conducted on cool nights. If you must use a flashlight, cover the lens with red plastic or cloth. Try to cover as much skin as possible with tight fitting heavy clothing.
Underground nests can be controlled by pouring the pesticide permethrin down the hole. Read and follow all label directions. Immediately after the application put a shovel-full of soil over the hole and run away, run far away.
Above ground nests can be dusted with cabaryl (Sevin) pesticide to coat the opening. Read and follow all label directions. The dust can also be placed on a small piece of steel wool or cotton to surround the hole. As the yellowjackets go in and out they get the pesticide on their bodies. As they groom, they ingest the pesticide. Nests should be killed in about five days. Never completely plug a hole going into the home if an active nest is present.