In February, the Washington State Department of Agriculture alerted beekeepers to keep watch for the Houdini fly — a pest of mason bees — that appears to be permanently established in the state.

The Houdini fly indirectly targets mason bees (also called blue orchard bees), laying its eggs on the pollen mason bees collected for their larvae. The fly maggots emerge first, eat the pollen and leave the bee larvae to starve. Researchers call this kleptoparasitism.

Mason bee producers and hobbyists should look for Houdini fly maggots in mason bee cocoons and destroy them. Purchasing bees from producers that inspect cocoons and using nesting materials that allow access to inspect for maggots will help to keep the pest in check, according to the WSDA pollinator health program. Controlling the Houdini fly in managed mason bees should also help to reduce the impact on wild bees.

More information is available online at

—by Kate Prengaman

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