Yellowjacket wasps live in large colonies dominated by a queen. Colonies start in the spring when the queen emerges from winter dormancy. Once she rears a few workers (female offspring) the queen no longer leaves the nest. Colonies grow throughout summer, reach maximum size by fall then begin to decline. Most nests die out before winter. Only mated queens survive until the following spring.
Colonies become aggressive in late summer
Wasps can be particularly aggressive in late summer when colonies reach maximum size. This aggression is generally associated with colony defense but wasp stings can occur away from the nest as well. If you get stung, get moving! When yellowjackets sting they may leave behind a small amount of chemical marker that identifies you as an enemy of the nest. For this reason you should quickly leave the area after being stung before other wasps have a chance to swarm.
Two types of yellowjacket wasp nest
Yellowjacket wasp nests are built either above ground or below ground (so called ground nests). Ground nests have a hole at the soil surface through which wasps enter and exit. For large nests this hole can be 2 inches (5 cm) in diameter. Aerial nests have a single entrance/exit hole usually near the lower apex of the papery nest (see photo right).
If either type of nest is built near human activity it may become threatening especially towards the end of summer. Aerial nests can be accidentally bumped and ground nests can be stepped on. Either case can result in swarming behavior and wasp attack. Threatening nests can be safely destroyed but keep in mind that most yellowjacket wasps are actually beneficial. These wasps prey on garden pests so only destroy nests that are actually threatening.
Do not treat wasp nests with gasoline or other flammable liquid. These liquids are both dangerous and illegal when used this way. Use the suggestions below instead.
Ground wasp nests
You'll probably discover ground nests in late summer by the wasp activity around the entrance hole. Hopefully you'll notice the opening before you step on it! Use a jet type aerosol to treat nests. This aerosol propels a narrow stream of insecticide about 15 feet so you can stand off a safe distance.
Approach the nest entrance carefully; stay back ten feet or more. In the evening, just before dusk, spray the entrance with about 1/2 can of solution then cover the opening with dirt or a rock to seal it.
Be cautious around the area of the nest for the next few days because on occasion the first attempt will fail and a new entrance hole will be opened. Repeat above procedure if this occurs.
Aerial wasp nests
Aerial nests, like the photo above, are normally easier to find but can be more difficult to control especially if located high above ground level. The same type of aerosol insecticide can be used on aerial nests but be very careful if the application requires climbing a ladder. Spray the area of the nest around, and into, the entrance hole. As with ground nests do this application in the evening. Remember, most yellowjacket nests are vacated by late fall so there is no need to destroy nests after about mid-September.
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