Yellowjacket Wasps

Yellowjacket wasps (often mistakenly identified as "bees") may become a nuisance around buildings. From August through October, when yellowjackets have built up large populations, they seek food such as carbonated beverages, cider, juices, ripe fruits and vegetables, candy, ice cream, fish, ham, hamburgers, hot dogs at picnics and other outdoor events. Many are attracted in large numbers to garbage cans. Others fly in and out of nests built around buildings and areas where people live, work and play, causing fear and alarm. Although yellowjackets are considered quite beneficial to agriculture since they feed on harmful flies and caterpillars, it is their aggressiveness and painful stinging ability that cause most concern. Nevertheless, unless the threat of stings and nest location present a hazard, it may be best to wait for freezing temperatures in late November and December, to kill off the colony. Stinging workers do not survive the winter and the same nest is not reused.

German Yellowjacket
The German yellowjacket is distributed throughout the northeastern quarter of the United States and often nests in wall voids and other cavities. (Other yellowjackets usually nest in the ground.) Nests in attics and wall voids are large and workers can chew through ceilings and walls into adjacent rooms. The nest of the German yellowjacket is made of strong light gray paper. Colonies of the German yellowjacket may be active in protected wall voids into November and December when outside temperatures are not severe.

Problems with yellowjackets occur mainly when:

• humans step on or jar a colony entrance
• a colony has infested a wall void or attic and has either chewed through the wall into the building or the entrance hole is located in a place that threatens occupants as they enter or leave the building or
• in the late summer months, they search for sweet liquids like ripe, fallen fruit, soft drinks and sweets at picnics, sporting events and other gatherings.

Yellowjackets are sometimes responsible for an infection following a sting. A contaminated stinger can inject the bacteria beneath the victim's skin. Blood poisoning should be kept in mind when yellowjacket stings are encountered.

 

Control and Management

Inspection
Sting victims often can identify the location of yellowjacket nests. Soil nests are often located under shrubs, logs, piles of rocks and other protected sites. Entrance holes sometimes have bare earth around them. Entrance holes in structures are usually marked by fast-flying workers entering and leaving. A nest high in a tree should not be a problem unless it is where it may be disturbed. Be sure to wear a bee suit or tape trouser cuffs tight to shoes.

Habitat and Harborage Reduction
Management of outdoor food sources is very important.

• Clean garbage cans regularly and fit them with tight lids.
• Remove trash that includes bakery sweets, soft drink cans, candy wrappers and other food waste several times a day from outdoors trash bins during periods of yellowjacket activity.
• Where possible, locate food stands away from dense crowds during the late summer.
• Clean drink dispensing machines; screen food dispensing stations and locate trash cans away from food dispensing windows.
• To limit yellowjacket infestations in wall voids and attics, keep holes and entry spaces in siding caulked; screen ventilation openings.
• If yellow jackets are entering rooms through windows, window screens should be installed in windows whenever possible.

Pesticide Application
When possible, treat after dark; workers are in the nest at that time. If nests are located high in a structure where there may be a danger from falls or electrical wires; maintenance staff who also do pest control may be wise to hire a professional pest control contractor to treat the nest.

Begin with the entrance hole in view and a good plan in mind.

• Wear a protective bee suit. Unless these insects can hold on with their claws, they cannot get the leverage to sting. Bee suits are made with smooth rip-stop nylon which does not allow wasps and bees to hold on. A bee veil and gloves are part of the uniform. Tape or tie off wrist and ankle cuffs to keep the insects out of sleeves and pant legs.
• Move slowly and with caution. Quick movements will be met with aggressive behavior. Move cautiously to prevent stumbling or falling onto the colony.
• Have equipment handy so one trip will suffice.

Application to Underground Nests

• Insert the plastic extension tube from a pressurized liquid spray or aerosol generator in the entrance hole; release the pesticide as indicated on the label.
• If the pressurized liquid spray includes chemicals that rapidly lower nest temperature (freeze products), be aware that it will damage shrubbery.
• Plug the entrance hole with steel wool or copper gauze and dust the plug and area immediately around the entrance with insecticide. Returning yellowjackets will land at the entrance and pull at the plug picking up dust. Any still alive inside will also work at the dusted plug.

Application to Wall Voids

• Be especially cautious when using ladders to get at wall void nests. Set the ladder carefully and move slowly.
• Approach the entrance hole cautiously; stay out of the normal flight pattern.
• Watch first. Observe whether yellowjackets entering the nest go straight in or to one side or the other.
• Insert the narrow diameter plastic tube in the hole in the observed direction of the entrance and release pesticide as indicated on the label.
• Dust inside the entrance and plug it as with underground nests.
• Remember, German yellowjacket nests may remain active into December.
• Use care not to contaminate food surfaces.

Control of yellowjackets with traps has not been effective with eastern species. Spraying trash cans and the outside of food stands will reduce or repel yellowjackets at sporting events; the treatment will not last long. Remember, do not contaminate food surfaces.

Follow-up
Ongoing monitoring throughout the active yellowjacket season is essential when a pest management program is in place at locations where there are outdoor activities. Whenever possible, screens should be installed in school room windows and garbage cans should have tightly-sealing lids.