by Chal Landgren, OSU Extension Christmas Tree Specialist
Anyway it is spelled- Yellowjacket, Yellow Jacket or Yellow-Jacket, these insects are feared and hated not only by picnickers, but by many working in the woods, and in Christmas trees. For Christmas tree growers they can inflict physical and economic pain, since they are unwanted hitchhikers in many shipping destinations.
First some biology- These are not honeybees. Rather, two predatory insects in the genus Vespula, whose common names are the Western Yellowjacket and German Yellowjacket. The Western
Yellowjacket (V. pensylvanica) is a common native. Yes, they are predators, but also scavengers, which makes them a pest at summer BBQs and picnics. The German yellowjacket (V. germanica) is an uncommon non-native species (not wanted in Mexico). Both these insects feed on other insects as well as nectar, honeydew and fruit.
Queens will overwinter in protected locations above or below ground and emerge in May. After the queen emerges she will begin her colony which eventually can include hundreds to thousands of workers. Fertilized queens will emerge again in October or November. Males (stingless) begin to emerge in large numbers in late July.
Control strategies are very time sensitive. Some growers have observed fewer nests being formed if they can get out their lure traps before the females start forming colonies (May). If you can trap a queen you can begin to control the populations. Once the females begin colonies they do not fly and the lure traps catch only workers or males. Workers can fly ¼ mile or so from the nest in search of food. That “food” can be honeydew from aphid feeding on Christmas Trees, if present.
Where they conflict with work or recreation, nests can be targeted with insecticides. The PNW Insect Management Handbook reminds us wasp nests should be treated in evening when wasps are less active with a pesticide formulated specifically for wasp nests (rather than gasoline), and also that some professionals in the PNW collect wasps to be used in the manufacture of allergy injections. Find more here.
There are registered baiting options that can be useful around homes, campgrounds and zoos. The insecticide Onslaught is a microencapsulated version of esfenvalerate (a pyrethroid) is approved for use in bait stations. A company out of Bend, Alpine Pest Management, makes the bait stations.