Bumble bees will avoid visiting flowers when an invasive bee, the European wool-carder bee, is nearby

Here's a press release about this work:

MEDFORD/SOMERVILLE (January 18, 2019) – Bees play a vital role in food production and reproduction of plants. Native bumble bees are particularly important pollinators as they visit a wide array of plants, and are particularly efficient at pollination. But researchers at Tufts University have recently shown that the common eastern bumble bee (Bombus impatiens) will avoid visiting flowers when an exotic bee species is nearby.

The European wool-carder bee (Anthidium manicatum) is native to Europe but is now present across much of North America. The wool-carder bee is a solitary species (it doesn’t live in a nest with other bees like bumble bees or honey bees) and the males of this species will defend patches of flowers. They have spikes at the base of their abdomen that they will use to ram into and injure other bees that try to access their defended patch. Only female wool carder bees are allowed in, which gives the male the opportunity to mate with her.

The aggressive defense of resources by male wool-carder bees has been a point of concern for bee biologists and invasion ecologists since wool-carder bees were first discovered in upstate NY in the early 1960s. However, no previous studies have measured the impact of wool-carder bees on native species in North America. Understanding the behavior of this invasive bee and its impact on native species was the focus of Dr. Kelsey Graham’s graduate work, advised by Dr. Philip Starks in the Biology department at Tufts.

Dr. Graham and Dr. Starks’ recent publication, in the journal of Biological Invasions, specifically looks at the impact of wool-carder bees on the foraging behavior of the common eastern bumble bee. They used screened research enclosures to observe interactions between foraging bumble bees and wool carder bees, and found that bumble bees will avoid foraging at flowers when wool-carder bees are around, missing out on valuable food resources.

“By avoiding resources associated with wool-carder bees, bumble bees have fewer flowers available to them in their environment. This is troubling, as native bees are already facing food shortages due to urbanization and agricultural land use,” said Kelsey Graham, who is currently working as a postdoctoral researcher at Michigan State University.

“European wool-carder bees are abundant in urban-residential areas, such as the neighborhoods around Tufts, as they prefer non-native ornamental plants, like mints, that people love putting in their yards,” explained Graham. “But by choosing these plants, that often means you are attracting wool-carder bees that attacks native bees and honey bees attempting to come and collect pollen and nectar. So what may look like a wonderful pollinator garden, may actually only be providing resources to wool-carder bees.” So, what can you do to help native bees?

Graham advises us to “instead, try to plant flowers that are native to your area. These will be more attractive to native bees, and perhaps limit the spread of this invasive bee. Blooming trees are also a great resource for spring bees, and aren’t visited by wool-carder bees.”

Check out these resources for establishing a pollinator friendly garden:

 https://www.northeastpollinator.com/pages/planting-for-pollinators 

 https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs144p2_027028.pdf 

 http://xerces.org/pollinators-northeast-region/