KENNEWICK -- Over the summer, I noticed lots of yellowjackets industriously foraging amongst my petunias and other flowers.
I kept a respectful distance, but they didn't pay any attention to me. I didn't realize at the time that they were not yellowjackets. They were paper wasps.
What's the difference? Yellowjackets are specific types of wasps. The western yellowjacket, the common yellowjacket and the German yellowjacket are the most common ones in Washington. Most are about a half-inch long and black in color with jagged yellow bands on their back.
An impartial observer might say that yellowjackets are beneficial insects because they're predators, feasting on other garden insects during the spring and early summer. They chew up their insect dinner, then feed it to developing larvae when they return to their nest. In repayment, the larvae feed the workers with a nutritious liquid that they produce.
In late summer and early fall, the sustenance provided by the larvae dwindles along with the ready supply of insect prey. Aggravated, hungry yellowjacket workers start aggressively scavenging for other sources of protein and sugar, such as soft drinks, picnic food, garbage, carrion and more.
Paper wasps, another specific type of wasp, are easily confused with yellowjackets. They look much like a yellowjacket except they have a slimmer, more elongated body and they fly with their legs dangling downward. The golden paper wasp is native to the west, but it's been displaced in urban areas by a non-native, the European paper wasp. These are probably the "yellowjackets" I've seen in my flowers. Paper wasps are also good predators, attacking soft-bodied insects, but the adult workers get their sustenance from flower nectar and other natural sources of sugar.
Paper wasps generally are not considered aggressive. However, they do sting when threatened with physical contact. The European paper wasp is not afraid of human activity, often building nests in protected spots around homes, such as under eaves, in retaining wall spaces, on play equipment, and patio furniture. That's why it's often the cause of many human insect stings in the Northwest. Gardeners who unsuspectingly come across a nest amongst their garden plants are frequently attacked.
(Wear your garden gloves.)
Fall is the season when yellowjackets become a hazard for anyone trying to picnic or eat food outdoors. In recent years, the western yellowjacket, has become a serious agricultural pest in orchards and vineyards at harvest time.
The invasive European paper wasp also has become a serious sting risk. That's why Dr. Peter Landolt, a researcher at the USDA Agricultural Research Laboratory in Wapato, has been working on developing chemical attractants for use in traps. He successfully isolated two compounds from fermenting molasses that can be used to attract yellowjackets, paper wasps, and hornets. These attractants are used in traps marketed as RESCUE! W.H.Y. Trap.
While there are numerous traps on the market that work fairly well for trapping yellowjackets, they don't attract paper wasps. The RESCUE! W.H.Y. trap attracts does. Traps are used most effectively when placed outdoors in early spring, when daytime temperatures are consistently 70 degrees or above. This catches the queens as they come out of hibernation and before they start new colonies. (The queens are the only yellowjackets and wasps that survive over the winter. New nests are built each spring.) If you have problems with yellowjackets or paper wasps, remember to place traps out early next spring.
* Marianne C. Ophardt is a horticulturist for the Washington State University Benton County Extension Office.