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Horticulture and Home Pest News
Horticulture & Home Pest News is filled with articles on current horticulture, plant care, pest management, and common household pests written by Iowa State University Extension specialists in the Departments of Entomology, Horticulture and Plant Pathology.

Bee-ware of Bumble Bees

This article was published originally on 8/25/1993
For reasons that are not yet clear tome, this has been a good year for bumble bees. In my own yard,bumble bees have been more noticeable as they forage for nectarfrom flowers of bee balm, St. Johnswort and other plants.

Bumble bees are big, fuzzy insects recognized by almosteveryone by their robust shape and black and yellow coloration.The common species are 3/4 inch in length or more. Like theirclose relatives the honey bees, bumble bees live in a colony wherethe adults care for the young (larvae) produced by a single queen.Bumble bee nests are small compared to honey bees, as each nestcontains only a few hundred individuals. Also unlike honey bees,a bumble bee nest is annual and is used only one year and thenabandoned.

Bumble bees usually nest in the ground in a deserted mousenest or bird nest. Occasionally they nest in cavities within awall or even in the clothes drier vent.

In the spring, the queen selects a nest site and starts thecolony by lining an existing cavity with dry grass or moss. Thenshe collects a mass of pollen and moistens this with nectar toproduce a stored food called "bee bread." Her first brood ofoffspring, numbering 5 to 20, will all be workers (daughters) whotake over the colony responsibilities of nest enlargement, foodgathering and storage, and feeding and caring for the larvae. Thequeen continues to lay eggs throughout the summer. By late summer,reproductive males and females are produced. These mate on thewing and the fertilized females move to hibernation sites in theshelter of loose bark, hollow trees or other dry, protected placesto lie dormant through the winter. The males and workers still inthe colony die with frost or the first hard freeze.

Along with the honey bees, bumble bees are very importantpollinators of flowers. Certain plants are better pollinated bybumble bees because of their very long tongues.

If the vicinity of a bumble bee nest can be avoided, thenleaving them alone and waiting for them to die in the fall would bethe preferred management option. However, bumble bee nests areoften found in yards, flowers beds, wood piles, or walls in hightraffic places where the threat of being stung is great.

Trapping bumble bees is not practical and exclusion techniquesmay not solve the problem. When controlling bumble bees isnecessary, using insecticides to poison bee colonies is the controlmethod of choice.

Bumble bees, honey bees and yellowjackets are all controlledthe same way. After determining the nest location and nestentrance during the day, wait until night to treat if possible.Wear long-sleeved shirt and trousers and tie sleeves and pants legsshut or pull your socks out over your pant cuffs.

Apply insecticidethrough the entrance hole. Dust formulations of insecticides arepreferred (e.g., Sevin dust). Use a duster or "fling" insecticideinto the hole off an old plastic spoon. Sprays and ready-to-use"wasp and hornet" aerosol sprays can also be used, but often withless satisfactory results.

Do not plug the entrance hole until all activity has stopped.Be prepared to repeat the treatment if necessary. Finally, sealshut, caulk and paint all openings in the vicinity of the oldentrance.

If the nest opening can not be reached because of shrubs orother obstruction, the area of bee coming and going (observedcarefully from a distance during the day) can be broadcast sprayedat night with an insecticide solution to kill the foraging workers.



This article originally appeared in the August 25, 1993 issue, p. 143.

Year of Publication: 
1993
Issue: 
IC-465(22) -- August 25, 1993