This is the time of year when populations of yellowjackets and other social wasps are large enough to be quite noticeable and when people determine 'something needs to be done.' The wasps have been present since spring, but populations were very small through the early part of the summer and didn't reach their peak numbers of approximately 5,000 yellowjackets per colony until late summer.
Yellowjackets build paper nests similar to hornets, but either in the ground, a log or landscape timber or building wall or attic. Yellowjackets are commonly observed hovering back and forth at the small nest opening or around garbage cans and other areas where they forage for food. The workers from the colony travel up to a few hundred yards from the nest while looking for food. In the early summer the wasps forage for caterpillars and other 'meat' items, but in the fall prefer sweets such as pop and candy residue in garbage cans.
If a nest is located where it is out of the way and not likely to be disturbed, it is best left alone. If, however, a nest is located in a 'high traffic' area such as along walks or near doorways, control is justified to reduce the threat of being stung.
Nests in walls or in the ground can be destroyed by placing an insecticide dust (e.g., Sevin or rotenone garden dust) in and around the nest entrance during the night. The dust particles will adhere to the insects as they leave and reenter the nest and control will usually be achieved within a few days. Do not plug a nest opening in a house wall until you are sure all activity within the nest has stopped.
For other kinds of wasps (hornets and paper wasps) that build above ground nests on trees and houses use the 'wasp and hornet' aerosol sprays specifically made for this purpose. These spray cans shoot the insecticide several feet. Treat nests at night when all of the workers are at the nest and the chances of being stung are lower. Retreat in 2 or 3 days if necessary.
Wasps or Bees -- How can you tell?
Many of the questions at this time of year about stinging insects mention 'bees' nesting in the wall of the house or in a hole in the ground. More often than not, these 'bees' are yellowjacket wasps. The following pictures and descriptions show the differences.
Honey Bee Size: approximately 1/2 inch long. Color: golden brown with thin black stripes. Body texture: generally fuzzy appearance; the thorax, especially, is covered with branched or plumose hairs. Leg characteristic: first segment of hind tarsus broad, flat and densely hairy (pollen collector). Wing characteristic at rest: wings lay flay and unfolded atop the abdomen. Nest site: in hives, house walls, hollow trees. Never in the ground. Nest material: wax. Nest contents: honey and stored pollen. Food: exclusively pollen and nectar, occasionally moist sweets such as pop residue.
Yellowjacket Wasp Size: approximately 1/2 inch long. Color: bright yellow with black lines, spots, triangles or diamonds. Body texture: hard and shiny; few if any hairs on the body. Body shape: thinner, more pointed abdomen than honey bee. Leg characteristic: first segment of hind tarsus not broad or flat (no pollen collector). Wing characteristic at rest: wings fold into a narrow strip atop the abdomen. Nest site: in the ground, retaining walls, house walls, hollow trees. Nest material: paper. Nest contents: no stored food. Food: other insects, sweet food residues.
This article originally appeared in the August 26, 1992 issue, pp. 145-6.