Wild bees key topic at MSU’s Pollination Forum

by Dean Peterson

“If we can foster (wild bees), it may be that we don’t have to bring in such large colonies of honey bees,” said Marla Spivak, professor in the University of Minnesota’s Entomology Department.

Honey bee colony losses have been well documented, but a recent Pollination Forum at Michigan State University presented by the Integrated Crop Pollination Project, showed reasons for optimism.

Wild pollinators, like mining bees, sweat bees, mason bees and bumble bees, have been found to be important pollinators in addition to honey bees.

“Wild bees make important contributions to crop pollination,” said Rufus Isaacs, MSU professor of Entomology and ICP Project director. “We need to be providing habitat to support all types of pollinators.”

“We have diverse populations of wild bees around our crops. If we can foster them, it may be that we don’t have to bring in such large colonies of honey bees,” said Marla Spivak, professor in the University of Minnesota’s Entomology Department, and featured speaker at the Pollination Forum. “We need new practices of integrated management of wild bees and honey bees.”

Wild bees have important differences from managed colonies of honey bees.

Honey bees have a forage range of at least two miles and reside in colonies of 20,000 to 40,000 bees. “Wild bees will forage within one-half mile from their nest,” Spivak said. Wild bees also tend to be solitary and most of them nest in the ground. About one-third nest in stems or tunnels.

Honey bees store pollen in the cells of the combs. When adult bees eat the pollen, glands in their heads are stimulated to produce food which activates detoxifying genes. “Adult honey bees can detoxify some of the pesticides in pollen,” Spivak said.

Wild bees store pollen directly in the nest. “Larvae feed directly on the pollen ball provisioned by the mother bee,” Spivak said. “The larval detoxification system is not fully functional. Wild bees are much more at risk.”

Recent MSU research measured whether adding habitat to fruit farms increases populations of wild pollinators. “We’ve seen increases in bee populations, but so far there is not statistically significant yield improvement,” Isaacs said. “Other studies show the benefits of habitat plantings develop over time, as native populations build. It will be interesting to see what happens next year in this study.”

The key questions are: how much habitat do growers need to plant and where do they need to plant it. The big question is, of course, will fostering native pollinators pay?

The stresses on honey bees come from many factors. The list includes the varroa mite, viruses—and varroa mite-virus complexes, other diseases, environmental problems, fungicides and herbicides, and flowerless landscapes.

“I keep coming back to what I call nutritional solutions,” Spivak said. “We have ways to control varroa mite but need more solutions. When bees have good nutrition, their immune systems can fight off some of these diseases. Good nutrition can help bees detoxify agrichemicals. Our bees can take care of themselves unless they’re highly stressed or have high levels of mites and viruses.”

The environmental challenges are big. Honey bees sweep the environment. Recent studies of pollen sacs show on average, each bee is returning to the colony carrying six pesticides.

Bees need areas to forage that are not contaminated with pesticides. “If there are flowers blooming, there’ll be bees foraging,” Spivak said.

“Wildflower borders enhance bee communities,” Isaacs said. Growers can be thinking about where pollinator habitat can be worked into their farm, perhaps in a cold spot in the orchard or an area with poor soil. The Farm Service Agency and Natural Resource Conservation Service both have programs to help growers select pollinator conservation practices for their farm, so starting at a local USDA service center or talking to the local conservation district is a good place to start.

Nesting tubes can be provided for some stem-nesting bees that can be great pollinators for spring fruit crops. The tubes can be replaced or cleaned to prevent disease spread. Wild bees that nest in the ground also need undisturbed soil.

“For pesticides, it is important to control drift, and use products with shorter residuals,” Spivak said.

The ICP Project is funded by USDA’s National Institute of Food and Agriculture and is in its fifth of five years. That milestone brought partners and supporters from around the country to East Lansing to discuss results and future directions.

Other Project ICP team participants at the Pollination Forum said:

“There’s a need for innovative practices. Some of the ideas that growers are considering include combinations of bees, planting flowers to enhance habitat, and keeping semi-natural habitat areas near farmland,” said Kelly Garbach, senior ecologist at the Point Blue Conservation Science, a non-profit conservation science organization based in Petaluma, California.

“We can see that honey bees and managed mason bees are both present in the almond, cherry, and apple orchards we are studying,” said Theresa Pitts-Singer, research entomologist at the USDA ARS Pollinating Insects Research Center at Logan, Utah. The center studies alternative pollinators in several states and several crops.

“In almonds, we have increases in fruit set, but do not yet see increases in nut yield attributable to the presence of wild bees. Populations of alternate pollinators take time to develop,” Pitts-Singer said.

There are 81 different bee species visiting crop flowers in orchards in Michigan, said Mace Vaughan, pollinator program co-director of The Xerses Society For Invertebrate Conservation in Portland, Oregon, a non-profit for wildlife protection. “Growers recognize we need other pollinators,” Vaughan said. “It’s all about setting up good communications with beekeepers.”

MSU’s Pollination Forum was sponsored by MSU’s Department of Entomology, College of Agriculture & Natural Resources, AgBioResearch and MSU Extension.