Addendum (2005): These mites are susceptible to dehydration in their early stages. The following combination of methods can achieve good control: 1) Use porous nesting materials, wood or, better, paper inserts in wood. 2) Take down the nest box early in the season, even before the females have made their last nests (about the last week in May in the Puget Sound area). 3) Incubate the larval nests in the nest box indoors under warm and dryconditions, ideally a mildly heated (up to about 85° F) and dehumidified room. 4) Starting about mid-August, check the nests periodically for mature adults. If you are using straw inserts, you can examine whole nests non-destructively by carefully slitting the straw lengthwise with a sharp blade. (Use of plastic straws for easier observation causes moisture problems, lowering bee survival and raising mite survival). Remove any remaining mite-infested cells. When all bees are mature, move to outside temperature for a few days, then into the refrigerator for winter storage (as nest inserts if using straws). Using these methods, mite infestation of about 50% has been reduced to 5%.
[Editor's notes: Information on the hypopus stages has been added to the original article. It is not completely certain that the mite we see in the Pacific Northwest is the east-coast C. krombeini; the European C. osmiae is recorded from Oregon.]
Baker, E.W. 1962. Natural History of Plummers Island, Maryland. XV. Description of the stages of Chaetodactylus krombeini, new species, a mite associated with Osmia lignaria Say. Proceedings of the Biological Society of Washington, 75: 227-236.
Fain, A. 1966. Notes sur la biologie des acariens du genre Chaetodactylus et en particulier de C. osmiae, parasite des abeilles solitaires Osmia rufa et O. cornuta en Belgique. Bulletin de la Société Royale Entomologique de Belgique, 102(16): 249-261.
Krantz, G.W. 1978. A manual of acarology. 2nd edition. Oregon State University Bookstore, Corvallis. 509 pp. P. 379, 419.
Krombein, Karl. 1962. Natural History of Plummers Island, Maryland. XVI. Biological notes on Chaetodactylus krombeini Baker, a parasitic mite of the megachilid bee Osmia (Osmia) lignaria Say (Acarina: Chaetodactylidae). Proceedings of the Biological Society of Washington, 75: 237-250.

This page last updated 26 July, 2005