Wild Bees Play Integral Role in Southern Wisconsin Agriculture

University Place: About 500 Species Pollinate Crops, Contribute to State’s Bounty
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The blue orchard mason bee is a pollinator of tree fruit crops.

Farmers around the United States are contending with the collapse of honeybee colonies they depend on to pollinate numerous crops, including many fruits, vegetables, legumes and nut trees. But growers in southern Wisconsin look to be in better shape because the Badger State is home to about 500 species of native wild bees that are excellent pollinators.

"Southern Wisconsin, I think, has a very health, robust wild bee community," said Rachel Mallinger. "We have a strong wild bee community that is providing really great pollination services for our crops."

Now a research entomologist with the U.S. Department of Agriculture, Mallinger offered this assessment when she was a graduate student in the University of Wisconsin-Madison Department of Entomology, in a March 26, 2014, presentation for the Wednesday Nite @ the Lab lecture series on the UW campus. Her talk about wild bees, their biology, and her research on pollination and the conservation of these insects in Wisconsin was recorded for Wisconsin Public Television's University Place.

Apple growers are highly dependent on honeybees and wild bees for carrying pollen among different trees within a species. Mallinger's research examined how effective wild bees and honeybees are at pollinating apple trees in southern Wisconsin orchards. She did not find any benefit to renting honeybees to pollinate these trees — Wisconsin's native bees can handle the task of producing an abundance of pollinated flowers to develop into fruit.

Mallinger also found that the greater the diversity of wild bees in a given area, the more pollinated flowers turn into fruit. Indeed, diversity of species is more important for pollination than the actual number of individual bees. Bees in different species interact while foraging, and force each other to move among more flowers, leading to additional cross-pollination.

With changes in how humans use and develop land, including for agricultural purposes, some species of wild bees are declining in number while others increase in abundance. Research published in 2013 on bees in the northeast United States found a given species' size, nesting site and whether it is parasitic affect its outlook — small bees and parasitic bees seem to be doing well.

Mallinger's research in Wisconsin also found that the number of wild bee species increased with the diversity of landscapes.

Wisconsin farmers, landowners and residents curious about these creatures can consult the WI Wild Bee Guide, which uses photos and questions to to identify specific species. Mallinger contributed to this project, which was developed through the Great Lakes Bioenergy Research Center.

Key facts

  • Wisconsin is home to 500 species of wild bees.

  • Bees, wasps, sawflies and ants are in an order of insects called Hymenoptera. But only bees actively collect pollen, in order to feed their young. Ants and wasps visit flowers for their nectar to get a sugar hit, while sawflies feed directly on leaves, pollen and nectar.

  • Bees are drawn to dense clusters of blooming flowers. The more flowers, the more bees will be attracted to it. A bee's favorite garden will have a minimum of three blooming plants throughout the year. That diversity will boost the bees' immune systems, especially in species with a long life cycle.

  • Flowers native to the Upper Midwest that are good for pollinators (bees and other insects) include: anise hyssop, blazing star, dotted and mountain mint, goldenrod, lupine, milkweed, prairie clover, purple and yellow coneflower, smooth penstemon, sunflower, white wild indigo and wild bergamot.

  • Wasps include yellow jackets, hornets and paper wasps. They are carnivorous. and feed insects to their young. Some wasps lay eggs inside live insects that the larvae eat as they grow, while others hunt insects or other arthropods their young to eat.

  • Honeybees are distinct from wild bees. European settlers brought the single honey bee species, Apis mellifera, to North America supposedly for harvesting their hives' wax and not for honey. Honeybees are currently raised mainly for pollination — they are very important for certain crops like almonds — and beekeepers will lease hives for this purpose, moving them from farm to farm.

  • Over the past decade, people have become increasingly concerned about declining numbers of honeybees though a phenomenon called colony collapse disorder. (The Bee Informed Partnership, a project of the USDA's National Institute of Food and Agriculture, reported in May 2016 that 44 percent of honeybee colonies were lost in the preceding year.)

  • Some wild bees nest underground. The female digs a long tunnel, creating a space for each individual offspring. She deposits a ball of pollen and nectar in this space, called a cell, and lays an egg atop it in the spring or summer, depending on the species. The egg develops into a larva, which consumes the pollen and nectar and becomes a pupa in fall. Some species transform from pupae into adults over the winter or in the spring, when the bees emerge to start collecting pollen and nectar, digging nests and laying eggs to renew the reproductive cycle. Bees that nest in the ground prefer well-drained soil that is relatively bare, without thick turf or dense prairie.

  • The bumblebee is the only truly social bee native to Wisconsin. Each bumblebee queen lives for a single year, with workers alive for a few months. Males live for a month or two. Even though the are social insects living in large colonies, bumblebees are harder to manipulate than honeybees because they're lifespan is shorter.

  • Even though honeybees are not essential for crop pollination in Wisconsin, they play an important role in other areas of the United States, particularly in California where land-use change has been extensive. These ecosystems depend on honeybees because wild bee communities are small and homogeneous.

Key quotes

  • On wild bees versus honeybees as crop pollinators: "Wild bees will not replace honeybees for the honey production, but they can replace them for pollination because they're very effective pollinators for crop and wild plants. … Honeybees are easy to manage because they are social, and you can bring them around in these large colonies … [but] aspects of wild bee biology makes them difficult to manage. So, with the exception of a few species, we're not quite sure how to manage wild bees and move them around the landscape. So that's why their use in pollination is limited."

  • On wild bees in the landscape: "Wild bees are just out there. They're living in areas that we're not really sure about. Some of them will be living near farms, others not, and so they're not just susceptible to what goes on on the farm, but they're also susceptible to what goes on in all of these other habitats as well."

  • On bees and land use: "So the larger the organism, the higher the resource requirements, maybe the more susceptible it is to changes in land use at these broader scales. … Agricultural habitat as well as urban habitat do have a place in bee conservation. So, somewhat surprisingly, we did not find more bees or a greater diversity of bees in, say, these heavily wooded areas or areas that were surrounded by preserved wetlands. … Many resources [for bees are] in urban habitats: Flowering trees, flowering gardens, woods, stems, bare ground for nesting. And similarly, for agricultural fields you can have flowering weeds, you can have field margins, and even the crop itself. So, diverse landscapes that can support both bees and human activities might be a nice compromise for bee conservation."
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