Pest Alert: Osmia – Blue Orchard Mason Bees

— Written By NC State Extension

Date: March 17, 2012

From: Mike Waldvogel and Patty Alder, Extension Entomology

Another solitary bee that will show up within next two weeks and likely generate some attention from homeowners is the Blue Orchard Mason Bee, Osmia lignaria. They’re about 1/2″ in size (males are slightly smaller & sleeker) and a dark bluish metallic color. Callers may tell you that the bees are boring holes in wood but these bees let someone else do the work. In nature, they will take advantage of hollow plant stems or galleries made by wood-peckers. They will take up residence in abandoned carpenter bee galleries (which is another good reason for caulking the holes!) Because they will clean out debris in the carpenter bee galleries (and people have short memories about last year), callers may often swear that the bees are causing new damage (or they just swear anyway!). Pesticides are not needed (and wouldn’t work anyway).

Blue orchard mason bees are valuable pollinators. Steve Bambara put together a nice Insect Note with information about the bees and also has tips for attracting the bees by providing a nesting site from an old piece of wood. You can actually do the same with a cardboard cylinder and paper (not plastic) straws IF they’re the correct diameter). This activity can make a good 4-H project or just something for the young (and young at heart) to try out to help our pollinators. Check out:

Updated on Mar 17, 2014
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