UW-Extension Workshop Offers Lessons on Native Pollinators
Posted October 2011
Stephanie Daniels, Points North
(Reprinted with permission from the Park Falls Herald)
PRICE COUNTY — A mix of casual gardeners and farmers who make a living in part through crop sales met at Tom and Mary Lou Nicholls’s Nature Education Center in Fifield Wednesday, Aug. 31, to learn about native pollinators—species that could play a vital role in preserving American agriculture if honeybees continue to see their current levels of decline.
Regina Hirsch, PhD, Eco-Fruit Outreach Specialist at the University of Wisconsin-Madison Center for Integrated Agricultural Systems, led the workshop centering around the characteristics and importance of native bees.
Honeybee colony populations continue to crash over the winter at levels that make beekeeping economically unsustainable. According to a USDA Agricultural Research Service news release, managed honeybee colonies across the nation saw an average population loss of 30% between October 2010 and April 2011.
This underscores the danger of relying on a single species to perform the valuable service of pollinating fruit crops, Hirsch said. The solution, along with finding ways to revitalize honeybee colonies, will be maintaining healthy levels of native bees, some of which, such as certain species of bumble bees, are also in decline, according to Hirsch.
Native bees as a rule are hardier and more productive than honeybees. For example, bumble bees remain “active in cooler, wetter weather,” Hirsch said. “It’s a plug for our bumble bees.”
Hirsch points out that honeybees also tend to pick up their movements in the presence of native bees, improving the efficiency of their pollination.
As one added benefit, native pollinators don’t come with the steep rental rates honeybees now tend to carry. The population of remaining honeybees is stretched further to keep up with the increasing acreage of certain crops. Colonies may be transported across country—an expensive undertaking considering the cost of fuel, Hirsch said.
Bees used in such widely traveling commercial operations are typically fed high- fructose corn syrup while on the road and pollinate acres of a single crop without clusters of other plants to offer dietary variety, which may lead to less healthy bees and potentially contribute to colony collapse, Hirsch explained.
Distinguishing native bees from flies and other mimics can be a bit tricky, but there are some telltale signs to look for that make identification easier, according to Hirsch.
Long antennas, four wings and a small waist are features that set bees apart from flies. Related predatory insects, like wasps and hornets, may resemble bees in form, but they lack the coat of hair and scopa—structures for collecting pollen—that assist bees in their pollination work.
Bees require food sources from the time they first begin to emerge in April until the adults begin to leave in October.
“It’s really key to have something blooming all the time. Otherwise, they starve,” Hirsch said.
Dandelions, squill and the Canadian white violet are some examples of flowers that bloom early enough to meet bees’ needs from the start of the season.
Bees only see blue, yellow, purple, violet and white, so flowers in a mix of those colors should be chosen when creating a habitat for them. Since bees come in such a diverse range of shapes and sizes and have different pollination approaches, Hirsch advises keeping three different varieties of flowers in each of these colors blooming throughout the growing season.
A complete list of bee-friendly flowers that thrive in each gardener’s region can be found at www.pollinator.org/guides.htm.
Hirsch recommends maximizing a property’s bee-feeding potential by planting flowers on buffer strips of otherwise unused ground, such as space leading up to a ditch. Ideally, multiple plants of the same species should be grouped in clumps to accommodate the pollination patterns of bees. They tend to fixate on a singular species for a time, using
collected pollen supplemented by a little nectar to provide food for their young.
Along with flowers in a variety of colors, shapes and sizes to suit the feeding needs of bees of all kinds, an ideal bee habitat includes appropriate nesting grounds for the four-winged insects.
“If you don’t have a nesting site on your land, you’re not going to have the diversity,” Hirsch said. Ground-nesting bees require small patches of soil to be left uncovered by vegetation for digging anthill-like tunnels in which to deposit their eggs.
Other solitary bees make their nests in hollow plant stems, man-made cavities, or holes bored into trees by other organisms.
Social species, such as bumble bees, will create a mass nest in a range of places, from an abandoned rodents’ nest to the side of a house.
Leaving some wild spaces nearby—within 500 feet to about a half-mile since most species have a relatively limited travel range—is also crucial to insure the feeding and nesting needs of most bee species are met.
Because of their very different nesting habits, a healthy population of bees is best supported by providing a range of plant materials, including leaf litter, brush piles, and a dead tree or two.
Pesticides should be used as minimally and carefully as possible in order to protect beneficial insects, including native pollinators, according to Hirsch.
Though some pesticides are more deadly to bees than others, any of the chemicals, by their nature, can pose a danger to the insects. “Pesticides are produced to kill, so just keep that in mind,” Hirsch said.
In many cases, there are more bee-friendly alternatives to keep pests in check. For example, a bacterial treatment, BT, shuts down the digestive systems of targeted pests in the larval stage without posing a danger to bees and other beneficials.
Some so-called organic chemicals used to control pests are just as deadly to bees as conventional pesticides, Hirsch cautioned. Pyrethrins, spinosads and neonicotinoids are some “natural” pest-killing compounds thought to pose a risk to bees.
If pesticides must be used, Hirsch emphasizes the importance of reading the label to make sure there is no warning about avoiding the use of the product around bees. Directions should be followed closely, and the smallest effective amount should be used.
“Don’t think that more is better. It’s not,” Hirsch said.
It’s crucial to avoid applying chemicals when plants visited by bees are in the blooming stages and bees are most likely to come into close contact with them and ingest or absorb their materials, according to Hirsch.
The University of Wisconsin Center for Integrated Agricultural Systems has been leading efforts to convince producers to switch to an integrated pest management system for protecting crops with considerable success; participation in the program has risen from an initial level of 17 farms to the current level of 70 over the last several years.
An integrated pest management strategy involves setting economic thresholds of the amount of fruit the producer is willing to lose before applying pesticides, monitoring pest levels, using least toxic options when chemical application is necessary, and limiting treatment to sites most affected by pests.
On average, participating producers reduced pesticide applications per season from about 27 to something in the range of 10 to 15.
The less pesticides are used, the greater the diversity of bee species tends to be in an area, according to Hirsch.
Diversity of bees helps promote strong crop production since different types of crops bear different forms of flowers best pollinated by bees with a specific set of traits.
Hirsch speculates that the dramatic decline in pumpkin production reported by one workshop attendant may be tied to a decrease in the population of squash bees, one of the leading pollinators of pumpkins and related vine crops. In a typical year, the Park Falls area farmer said he could expect to harvest between 3,000 and 6,000 pumpkins per acre planted; the number pulled out of the vines dropped to 1,200 fruit per acre in 2009, then 400 over the 2010 harvest season.
Workshop participants got the chance to practice identifying bees and mimics they caught with butterfly nets between rain showers. Hirsch encouraged them to do the same at home so they’d have a better idea of the range of native pollinators working in their own gardens.