Bumble bees are social insects that nest in protected places: belowground in abandoned burrows of small mammals, in birdhouses, stuffing in abandoned furniture, or under piles of grass or rags in sheds or barns. They visit flowers to collect pollen to feed their larvae and nectar that provides them with energy.
Bumble Bee Reaction to Nest Disturbances
Bumble bees are not aggressive while visiting flowers (Figure 1). However, they will react strongly to any disturbance of their nest. Most stings in structures are the result of a person accidentally encountering a nest while searching for something or cleaning out an undisturbed area. Ground nesting bumble bees may attack a person who is pushing a lawn mower over a nest opening. The bees first react by buzzing loudly, and then they fly out to attack the intruder. While the barbed stingers of honey bees remain in the skin, the needle-like bumble bee stingers are smooth, so they can sting several times and inject venom.
Reaction to Bumble Bee Stings
Allergic reactions to bumble bee stings are much less common than to honey bee stings. The reaction varies with the person, previous exposure to stings, location on the body, and number. The site usually swells and itches for a few several days before gradually subsiding. Multiple stings may cause a more serious reaction, such as vomiting or difficulty breathing. Severe reactions include dizziness, excessive sweating, and cold shivers. These symptoms usually develop within a few minutes and may require immediate medical attention.
Dealing with a Bumble Bee Nest
Long Term Solution
It is risky to treat or destroy an active bumble bee nest. If practical, leave it alone and avoid the area until fall. All bumble bees, except a few queens, will die at the end of the season. The queens will leave the nest to find shelter for winter. The workers will die, leaving an empty nest that can be removed without the risk of being stung.
Fill tunnels and holes in lawns and landscape beds with dirt so they will not attract queens looking for nesting spots in spring.
Short Term Solution
In some situations, it is not practical to wait for the colony to end naturally, so some control action is necessary. Several household insect control products (aerosols, dusts, and ready-to-use (RTU) sprays are labeled for bee and wasp control indoors and outdoors. Dust formulations can be puffed into nest openings and are especially effective at treating the insects as they enter and leave. Wear protective clothing and treat at night, if possible. Repeat the treatment if bees remain active for more than a day or so. Insect foggers are not a good choice for this type of control effort.
By Lee Townsend, Extension Entomologist