Vespula pensylvanica, (Western yellowjacket), Vespula germanica (German yellowjacket), Vespula vulgaris (Common yellowjacket)
Vespula alascensis (vulgaris) worker. (Photo courtesy of Oregon Department of Agriculture.)
Workers are approximately 13 mm (1/2") long; queen is 18 mm (3/4") long.
Black and yellow in color
German yellowjacket, though not common in Oregon Christmas tree fields, is the only wasp on the quarantine pest list for Mexico. (See
Pest Quarantine Information.) All
Vespula yellowjackets are quarantine pests for Hawaii. (See Pest Quarantine Information.) Biology and life cycle
Yellowjackets feed on insects, nectar, honeydew, and fruit.
Workers can fly up to 400 meters (1/4 mile) in search of food.
Yellowjackets are social insects with one queen per colony and often hundreds to thousands of workers.
Queen overwinters in protected locations.
Overwintering queen typically emerges in May.
After emergence, queen builds nest above or below ground and begins to produce workers.
Queen stays in nest through the growing season.
In August through October, new males and queens are produced.
Queens with fertilized eggs search for an overwintering site in October or November.
Queens and males may be active during shipping season, and queens may seek shelter in baled trees.
Yellowjackets often seek shelter on baled trees at harvest. (Photo courtesy of Oregon Department of Agriculture.) [Top]
V. atropilosa, V. germanica, V. pensylvanica, V. vulgaris. (Photo courtesy of Oregon Department of Agriculture.) [Bottom]
Look for yellowjackets attracted to honeydew in aphid-infested trees.
Yellowjacket traps can be placed in the field for monitoring. (See
Overview of Trapping and Monitoring Options.) Look for nests in the field and surrounding areas.
Look within branches and around baled trees stacked for shipping.
Some trading partners, such as Mexico and Hawaii, have zero tolerance for some or all yellowjacket species.
Trapping in the spring kills queens and prevents nest building, whereas trapping in the summer and fall kills workers and reduces populations.
Chemical lures/attractants are species-specific; food attractants are not.
Treat nests with approved insecticides.
Manage other pests, such as aphids, that attract yellowjackets.
Shake trees according to compliance agreements for destination countries. (See
Best Management Practices at Harvest.) Remove shaking debris frequently and keep debris separate from trees so pests are not reintroduced.
Apply approved pyrethroid sprays to trees in the field 3 to 6 weeks prior to cutting to meet current requirements for Mexico. Note: These sprays should not be relied upon as the only control method and may cause secondary pest outbreaks.
Exclude yellowjackets from trucks on warm days by closing trailer doors or using netting.
Minimize the time that trees remain in stacks. A second shaking just prior to loading can be effective.
Do not put “bug bombs” in Christmas tree containers —
this is illegal.
Look for eggs: May through October
Look for males: August through October
Look for queens: all year
Scout fields for presence of workers and nests: June through August
Trap queens: in May
Trap workers and treat nests: June to September
Shake harvested trees: October through November