Providing habitat for wild bees

Carole Curtis

PULLMAN, WA - It is a myth that humans can live without pollinators.

Using buckwheat as a cover crop or rotating crops with rye/vetch mixes are two of the techniques that benefit native bees and farmers' yields.

"The human diet and human health relies on pollinator-produced food," Elias Bloom, Washington State University, said during the third Integrated Crop Pollination (ICP) webinar in a series being presented by eXtension as part of a USDA-funded research project on promoting bee health and pollination services.

Bees, in particular, are important to global agriculture because of the billions of dollars worth of pollination services they provide annually.

However, wild bees are becoming increasingly rare or even extinct. For instance, 50 percent of all wild bees in Illinois have gone extinct in the past century, Bloom said. "We know there are massive range contractions and a severe loss of bee abundance, particularly in the farming regions," he noted.

Fortunately, hedgerows, windbreaks, filter strips, fallow fields and rotating crops offer farmers conservation opportunities for bees and other pollinators. In return, farmers gain valuable pollination services.

There is much research indicating ecosystem services increase with pollinator diversity. "We know that relying on bee communities, rather than populations of a single species, means more effective pollination," Bloom explained.

Since increased floral diversity appears to improve bee health, providing extra floral resources and reducing pesticide use would be in agriculture's best interest.

Bloom is involved in a on-going five-year investigation of wild bees on diversified farms that began in 2014. The goal is to understand how habitat and forage influences bee diversity and pollination services and how to best manipulate habitat and forage.

Connecting to the farm

The research shows promise. "No change is too little to undertake", Bloom pointed out.

The evidence suggests that farmers, especially organic practitioners, who create and maintain nest substrata for cavity-nesting bees can build abundant communities of wild bees.

To that end, the WSU researchers have been putting up structures with a variety of different diameters to provide habitat for bees that nest in cavities. "I'm hopeful we'll find providing habitat like this does increase pollination services," Bloom said.

Undisturbed ground space is also very valuable, since 70 percent of wild bee species live in the ground.

Floral buffer strips are also beneficial, resulting in a documented increase in the number of native bees and a significant increase in the number of bee visits to adjoining crops.

Farms with high plant diversity have significantly more bees than those with low plant diversity, Bloom confirmed. The correlation between floral diversity and bee biodiversity is strong: if there is an increase in plants in the cropping system, there is an increase in bee diversity and richness.

"Consider introducing floral diversity, either on the margin of your farm or intentionally within your fields," Bloom advised.

The evidence also indicates native plants are the most effective for wild bee management. "Native plants get more bees on the farm. You want to emphasize bloom, species diversity and structure," Bloom advised.

Research shows farming systems can increase bee abundance and pollination of crops, such as like alfalfa. Going organic certainly helps. "Switching from conventional to organic can increase bee abundance and richness by up to 75 percent," Bloom noted.

Roadsides and power line easements may also offer opportunities to expand and improve habitat for pollinators, helping increase their abundance and services. "We have to encourage policy at the local, state and national level of government to work with us on these types of projects," Bloom said.

Conservation of natural lands is also important, since research shows some bee groups are difficult to restore on the farm, but can and do live in natural lands adjacent to farms, which then benefit from their services.

Go native

Bridget McNassar, manager of Oxbow Farm's native plant nursery, described a native plant as one that has existed in an area since pre-European settlement days. It has adapted to the local environment and requires minimal care to survive.

"Native plants are ideal for wild bee habitat. They have coevolved with native bees and can be up to four times more attractive to them," she said, noting nectar and pollen may be lost or lacking in modern breeding schemes.

The first step is to find what plants are appropriate to the region. Visit the Xerces Society's Pollination Conservation Resource Center, which breaks the U.S. down into 10 eco-regions and gives recommended pollinator plants for each. Pollinator Partnership ( does the same but breaks the nation into 32 regions.

Choose a variety of species and a variety of various bloom times, she advised. Plan for some plants blooming from as early as possible to as late as possible, with emphasis on the early bloomers when bees are trying to build the first of several generations and resources can be scarce.

Aim for a variety of appearances in terms of color, flower shape, plant structure and height, since different bees are shaped differently and have different tongue lengths.

Incorporate native bunch grasses, which provide overwintering habitat and nesting resources.

When buying native plants or seeds, bear in mind that locally-grown and sourced plants have a better chance of surviving and thriving in the particular area. Also, be aware that "wildflower" does not necessarily mean "native", so clarify that the plant in question is a "native wildflower".

Resources include books like "100 Plants To Feed The Bees," available in pdf form, and "Farming for Bees," available from Xerces Society.

"Pollinators of Native Plants" and "Bees: An Identification and Native Plant Forage Guide," both by Heather Holm, cover the Midwest and Great Lakes regions.