| Pollinator Profiles
More than 270 species of bees are native to Maine. Here are a few that you might see in your meadows and crops this summer: Bumblebees (family Apidae) – Sixteen species of bumblebees live in Maine, ranging in size from under 1/2 inch to about an inch long. They are hairy, and usually black with yellow or orange stripes, although some have white markings. Like honeybees, bumblebees are social, but their colonies are smaller. They usually nest in abandoned rodent burrows in the ground, but may also nest in a cavity in a moldering hay bale or stump. Sweat Bees (family Halictidae) – Sweat bees are small, either green or brown, with stripes. They are usually the most abundant group found on farms and build their nests in the ground or in rotten wood. Some species are solitary while others are social, with anywhere from one to a few queens. You’ll often find sweat bees on composites, such as black-eyed Susans, sunflowers and asters. Plasterers (family Colletidae) – Plaster bees are so named for lining their brood cells with a cellophane-like substance. Yellow-faced plasterers are relatively hairless and look a bit like wasps. They nest in twigs and plant stems. The other plasterers (Colletes) are very hairy with conspicuous white stripes on their abdomen. They nest in the soil. Carpenter Bees (family Apidae) – These large bees are often mistaken for bumblebee queens, but they are hairless, with shiny black abdomens. Carpenter bees are solitary and bore into wood to create nests. Sometimes they “cheat,” stealing nectar through holes they cut in the sides of flowers – thus bypassing pollination. Miner Bees (family Andrenidae) – These small to medium-sized bees nest in the soil, often hiding their nest entrances beneath leaf litter. They are solitary bees, active in spring, and are the most frequent pollinators of blueberries. Leafcutter Bees (family Megachilidae) – Leafcutters are medium-sized black bees, often with a striped abdomen. They have relatively large heads with large mouthparts for cutting leaves, which the bees use to construct the cells they build in hollow plant stems. Mason Bees and Osmia (family Megachilidae) – This group contains small to medium-sized bees that are deep metallic blue or black with white hair on their thorax. Solitary bees, they nest in hollow plant stems or holes made by beetles. They need mud near their nest. This group is an important blueberry pollinator. |
by Sue Smith-Heavenrich
Colony collapse disorder (CCD) may not be making headlines lately, but the strange disease is still plaguing U.S. beekeepers. Between September 2007 and March 2008, commercial beekeepers lost close to 36 percent of their colonies to CCD, an increase of more than 11 percent over the previous year.
Honeybees provide valuable pollination services worth an estimated $14 million to U.S. agriculture alone, and the decline in honeybees is already affecting food production. Large scale almond producers and fruit and vegetable growers are concerned about crop losses due to lack of pollination services. And we’re not the only ones.
Italian growers claim they have suffered $100 million in losses directly attributed to the decline in their honeybee population, and experts say the cherry crop there could be wiped out within a few years. Farmers from across Europe report an estimated $1.25 billion in losses due to disappearing bees.
As Colony Collapse Disorder continues to take a toll, some farmers are wondering whether – and how – they can get native bees to take up the slack.
Native Bee Pollinators
Most people are familiar with bumblebees, the fat, hairy “teddy bears” of the bee world. But more than 4,000 species of native bees exist in North America, ranging from the size of a fruit fly to nearly 3 inches long. Like their honeybee cousins, native bees work hard to gather pollen to feed their young and in the process pollinate such crops as tomatoes, eggplant, watermelons and other melons, zucchini, cucumbers, winter squash and pumpkins. They also pollinate strawberries, raspberries and blueberries. In fact, over 80 species of native bees pollinate berry crops in Maine.
Native bees work harder than honeybees. Squash bees get up earlier in the morning and bumblebees keep working in cold and wet weather. Not only that, but an acre of apple trees can be pollinated by only 250 blue orchard bees (Osmia) – a job that normally requires 15,000 to 20,000 honeybees.
Native bees also make honeybees work harder. Scientists studying pollinators on hybrid sunflowers discovered that when wild native bees were around, honeybees were up to five times more efficient in pollinating the sunflowers. Apparently the natives made the domesticated bees nervous, causing the honeybees to switch flowers more frequently.
Attracting Natives to the Farm
“Let things go a little wild,” says Teresa Vanek of Red Tail Farm in Trumansburg, New York. Vanek and her partner, Brent Welch, raise bees, sell honey and grow vegetables on their 4-acre organic farm. Last winter they lost one hive, but Vanek says that was due not to CCD but to mites.
Vanek and Welch manage their farm in a way that supports their honeybees and provides food and habitat to wild pollinators – by having lots of flowers to provide nectar, for example.
“As we harvest, we leave older brassicas in the beds to flower instead of pulling them out,” Vanek explains. Bees love the yellow and white flowers produced by arugula, radishes, mustards and broccoli-raab. Vanek and Welch also allow their cover crops to flower. Buckwheat, white clover and red clover are part of the rotation, and Vanek says that they’ll plant white clover in the paths this year. In addition, Vanek plants a block of sunflowers each year to attract pollinators.
Does it work? Vanek thinks so. “We do have a lot of wild bees,” she says, noting that bumblebees and sweat bees are abundant on her crops.
Instead of managing wild bees, Vanek and Welch manage the bees’ habitat. They have developed a cropping system that provides an income and a desirable habitat for wild bees.
Four Steps to Attract Bees
1. Reduce or eliminate the use of pesticides.
Studies show that the use of pesticides, even on land beyond the farm boundary, is linked to wild bee decline. In the early 1970s, blueberry farmers experienced a sudden loss in their harvest after aerial spraying for spruce budworm in adjacent forests killed a large number of bumblebees, mason bees and mining bees. More recent studies show that native bee populations drop by around 50 percent where insecticides have been sprayed.
Low doses of pesticides that don’t kill bees outright may cause behavioral changes or other effects. Sheila Colla, at York University in Toronto, showed that bumblebees are paralyzed by neonicotinoids at levels as low as 12 parts per billion.
Organic farmers concerned about pollinator abundance may need to convince their neighbors to embrace IPM. Through scouting and well-timed pesticide applications, utility right-of-ways and other managed landscapes can be managed in a more bee-friendly manner.
2. Restore natural landscape.
Farmers hoping to attract wild bees need to provide a diverse, natural landscape including wooded areas, pasture, hedgerows and even rocky, dry areas unsuitable for farming.
“Intensive agriculture is not good for wild bees,” says Claire Kremen, University of California Berkeley professor. To test whether organic farms have more wild bees than conventional, she compared both systems in Yolo County. She noted that conventional farms were up to 10 times larger than organic; and the organic farms produced a diversity of crops, while the conventional farms tended toward monoculture. Also, organic farmers tolerated weedy borders.
By contrast, farms in New Jersey and Pennsylvania tend to be smaller, with more crop diversity. More important, though, eastern farms tend to be bordered by patches of forest. When Kremen sampled the wild bee community, she counted close to 40 species. On all these farms, she noted, the wild bee community was sufficient to provide pollination services.
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| Coneflowers and sunflowers are two species to add to farms and gardens to attract pollinators. Sue Smith-Heavenrich photos. |
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Numerous studies show that fields closer to natural areas – woods and uncultivated pastures or meadows – have more wild bees. This has to do with foraging range. While honeybees readily fly 2 miles to collect nectar and pollen, wild bees rarely fly over 1/2 mile. Lora Morandin, at Simon Fraser University, notes that while bumblebees will fly from 1475 to nearly 2500 feet on a foraging expedition, other wild bees forage within 500 feet of their nesting site.
3. Provide nectar sources.
Farmers who plant blocks of flowers or flowering hedgerows attract more wild bees to their fields. From a bee’s point of view, the problem with agriculture is that all the flowers bloom at once over a short period. Bee-friendly farmers need to provide food resources throughout the season.
The easiest thing to do is to encourage flowering trees and shrubs, such as red maple, raspberries and Amalanchier, to grow in your hedgerows. Leave 5-foot-wide grassy strips around fields, mowing them only after the weeds have finished flowering. Another way to increase nectar resources is to allow older brassicas or herbs such as oregano, thyme and sage to flower.
More active management of bee habitat includes planting cover crops and allowing them to flower (but not go to seed), incorporating multi-cropping in your fields, and planting infield insectary resources, such as sunflowers, bee balm and other bee favorites. Just planting one row of sunflowers per acre is enough to bring in bees.
4. Provide nesting sites.
Most wild bees are solitary, and about 30 percent build their nests in wood. They tunnel into the soft pithy centers of some twigs (raspberry canes and sumac) or use tunnels left by wood-boring beetle larvae. Carpenter bees excavate their own tunnels, and one important watermelon-pollinating species tunnels into soft, above-ground rotting logs and stumps.
The other 70 percent of the wild bees are ground-nesters, digging narrow tunnels down to small chambers of brood cells. Depending upon the species, nests may be 6 inches to 36 inches below ground. Ground-nesting bees need direct access to the soil surface and prefer sloped or well-drained sites. Bumblebees, too, build their colonies underground, moving into abandoned rodent burrows.
| Good Plants for Bees * indicates plants that are known to attract native bees in Maine Red maple (Acer rubrum)* |
Encouraging wood-nesting bees can be as simple as retaining dead or dying trees and branches in hedgerows and encouraging the growth of elderberry, blackberries and raspberries, sumac and dogwood. To attract ground-nesters, leave a small area untilled for a year or actively clear some vegetation from a gently sloping or flat area.
Making your farm bee-friendly takes planning, but you should realize a pay-off in higher yields. More important, encouraging native bee populations on your farm gives you “pollinator insurance.” By developing a diverse workforce of pollinators, you decrease the chance that poor weather or a bee disease will result in poor pollination of your crops.
Resources
Farming for Bees: Guidelines for Providing Native Bee Habitat on Farms, by Mace Vaughan, Matthew Shepherd, Claire Kremen and Scott Hoffman Black. 2007, The Xerces Society. This 43-page book is available as a pdf download or for purchase ($15); see www.xerces.org/guidelines/
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GE Crops and Native Pollinators
In 2005, Lora Morandin published a study comparing wild bee abundance and seed production in conventional, organic and genetically engineered (GE) canola. Morandin found the highest amount of pollination in organic fields and the least in GE fields. Her finding generated a flurry of interest in the media warning about the effects of GE crops on pollinators.
While GE crops have been shown to affect a number of insects, Morandin believes that the lack of pollinators has to do with the cropping system, not the GE crop. She noticed few flowering weeds in the GE fields, not enough to attract wild pollinators.
Morandin noted in her study that fields on the organic farms were smaller, with less crop area in relation to uncultivated adjacent area than in the larger GE fields. She believes this is significant, for in other studies she has shown that wild bees tend to forage 500 to 750 meters from their nests. Therefore a small field surrounded by uncultivated land would attract more bees than a quarter section field in the midst of similar fields. (Ecological Applications 15 (3) 2005: 871-881)
