An old answer to a new question?
While most of the $20 billion of U.S. agriculture production is pollinated by honeybees, there has been trouble lately with the important work that these European bees do. There have been diseases, mites, aggressive strains of Africanized honey bees and, lately, colony collapse disorder, which hit 25 percent of all commercial hives.
While the commercial bee industry has rebounded somewhat, these worrisome trends have growers concerned about their heavy reliance on European honeybees to do the critical job of pollinating their crops. The unrelenting honeybee crisis has also put a pinch on growers’ already strained pocketbooks. Renting commercial hives has spiraled from about $50 per hive three years ago, to $150 to $200 per hive (prices at the height of the California almond plant pollinating season this year).
One possible answer is to turn to bees that growers have relied on for generations before European honeybees made landfall in North America: native bees.
The unsung work of native bees
There is an impressive diversity of native bees across North America. Over 4,000 species have been identified, ranging from 1/8 inch long to more than 1 inch long. They also may not look like a typical honeybee: they can be dark brown, black, metallic green or blue, and can have stripes not only of yellow, but also of red, white or orange.
Some names given to the bees hint at the way they build nests: plasterer bees, leaf-cutter bees, mason bees, carder bees, digger bees and carpenter bees. Other names point to the way these bees look, act or the flowers they prefer, such as cuckoo bees, that lay eggs in the nests of other bee species, much like the cuckoo bird does; sweat bees that drink perspiration; bumblebees, from their sound; and squash bees that rely on cucurbit plants for their existence.
These bees neither live in large communal hives or produce enough honey to harvest. Many live in small communities in tiny holes in the ground or in wood, collect both pollen and nectar (as opposed to just nectar, as honeybees do), and many more live in solitary nests and raise their young alone. Because these bees don’t have a hive to defend, they are gentle and rarely sting.
With a little tweaking from growers to make a habitat conducive to native bees mating, eating and raising young, these tiny workers will gladly pollinate acres of crops with more efficiency than the honeybee, says Mace Vaughan, conservation director and entomologist/educator with the Portland, Ore.-based Xerces Society for Invertebrate Conservation (www.xerces.org). Xerces is an international, nonprofit conservation group that promotes the use of native bees to pollinate commercial crops.
On a per-bee basis, native bees are far more effective at pollinating apples, cherries, squash, watermelon, blueberries, pumpkins, sunflowers and cranberries, says Vaughan. Studies have shown, for example, that only 250 female orchard mason bees are necessary to pollinate an acre of apples. About one to two hives of honeybees would be necessary to do the same job—a total of 15,000 to 20,000 honeybees.
There are many reasons why native bees are more effective pollinators, Vaughan says. “They are not picky about weather conditions as the honeybee, and will continue to work in the rain and cooler weather,” says Vaughan. Native bees also pollinate using “buzz pollination,” where they grab onto a flower’s stamens and vigorously vibrate, releasing the pollen more effectively (a technique that is very effective for cross-pollination of blueberries, cranberries and peppers).
Little research has been done on native bees, but Vaughan suspects that native bees are quietly pollinating more crops on farms than growers suspect. One recent study (conducted by Rachael Winfree, Department of Ecology and Evolutionary Biology, Princeton University, Princeton, N.J.; Neal M. Williams; Jonathan Dushoff, Department of Biology, McMaster University, Hamilton, Ont., Canada; and Claire Kremen, Department of Environmental Science, Policy and Management, University of California, Berkeley, Calif.) conducted on farms in eastern Pennsylvania and throughout New Jersey, found that 90 percent of the pollination work was done not by the honeybees that were shipped in, but by native bees. One of the biggest factors in encouraging native bees to work these farms, oddly enough, was the tidiness of the farm. “Those growers that allowed weeds to bloom on their property had more native bees,” he said.
Fifty-four native bee species visited the farms in the study; most farms were conventionally managed and farmed intensively, but because most of the farms were small and had diverse landscapes (more roads, woodlots, weed-filled corners) native bees were able to thrive. “All these habitats, cobbled together, made an excellent place for these native bees,” said Vaughan. “The take–home lesson is that growers can just have these habitat patches and the bees will do fine … this can translate well for even big agricultural farms.”
Welcoming native bees on your land
Life hasn’t been easy for native bees, either, with studies indicating that their populations are also on the decline. The reasons may have to do with the monocultures on large farms, which make it difficult for native bees to eke out a living; the pervasiveness of fence–to–fence planting; tilling, which kills the young in the nests of ground dwelling bees; and the application of pesticides. Native bees are more productive on smaller farms with a variety of crops and more natural areas such as forests or meadows nearby, and on growing land that is easy on pesticides, uses “lighter” pesticides or only sprays at night.
“Native bees have disappeared from farms as agriculture has moved to large monocultures, such as 100 acres of one crop,” says Vaughan. Monoculture crops also bloom all at once, then the food is all gone for the native bees. “Monoculture crops are more efficiently pollinated by honeybees that are trucked in,” he says.
Even in monocultures, native bee habitat can be revived and native bees can return to help the honeybees with their work. In fact, even in these barren landscapes, studies have found that up to 30 percent of crops are still pollinated by native bees. “How we manage our lands can encourage native bees to return to nesting on the land and pollinating our crops,” said Vaughan.
“If we provide habitat on farms for native bees, it can provide pollination insurance for growers,” agrees Rex Dufour, California regional office director for the National Center for Appropriate Technology based in Davis, Calif., whose background is in pest management and studying beneficial insects.
Growers who depend on pollinators are already aware of how necessary it is to be careful about pesticides, for example, when crop is in bloom. Native bees are active both before and after crops are blooming and need food, shelter and care with pesticides throughout the entire growing season.
There are three simple steps that both ATTRA and the Xerces Society recommend to encourage native bees to live happily on your land:
1. Provide Shelter
Native bee pollinators are divided into two major groups: ground and cavity–nesting. For cavity nesters, make sure there are plenty of trees, hollow stems and plants on your property. Leaf-cutter bees will dig holes in wood or hollow plant stems. “These can be artificially developed,” notes Dufour, with simple blocks of wood with holes drilled in them to encourage nesting. For ground-dwelling species, avoid tillage or heavy mulch. “Lots of mulch doesn’t allow access to the ground,” said Dufour. Tillage can kill nests. “No-till agriculture is a growing phenomenon in the Midwest, and can help these bees,” he said. However, it is harder to practice no-till in the irrigated western part of the United States. Leave fallow areas—if a particular area of your land does not grow well, let it grow wild instead to provide nesting area for bees.
2. Provide Access to Food
Hedgerow flowering shrubs provide nectar and pollen in the early spring; perennials allow year-round food sources. “Try and get native perennials and annuals,” suggests Dufour. Leave weedy areas alone, and don’t clean up your farm too much of these plants. Avoid planting rows from fence to fence—leave some weeds at the end of each row. “A less ‘tidy’ farm with some weeds here and there is more likely to attract native bees than a picture-perfect farm,” said Vaughan.
3. Go Light on Pesticides
Bees, being insects, don’t do well when insecticide is sprayed wholesale on plants—even organic pesticides such as Pyrethrum can be harsh on native bees. It is, however, possible to use pesticides in ways that do less damage to bees. Apply pesticides during the evening or any time the bees are not active. Select insecticides with a low half-life and that will be photodegradable.
While the call for commercial bees will continue to be strong because of the ability to move honeybees around to where they are needed, incorporating these simple habitats for native bees on your farm could reduce the need to hire expensive hives. You might consider talking to nurseries to find out how to maximize floral diversity before and after your particular crop blooms to get the right native flowering species.
“Farmers can understandably be risk–averse and won’t change their use of commercial bees until they see a real need,” said Dufour. “But, these changes to encourage native bees don’t cost a lot of money and will ensure that if commercial bees are scarce, that growers will have pollination of their crops, regardless of the availability of hives or the weather … I believe that once growers realize that this is an option, they will begin to move in this direction.”
What is needed is more research on the service these native bees can provide for growers. “It is a subject that has been largely ignored because the economic viability wasn’t known,” said Dufour. “And, we have been inadvertently killing them off by erasing their habitats because of ignorance. These bees are like livestock … you can’t put a cow herd in the middle of a desert and expect it to do well. But, if growers just tweak their land a little, and understand this ‘livestock’ and nurture it, I think they’ll get a lot in return from these beneficial native bees.”
The author is a freelance writer from Keene, N.H.
For More Information
ATTRA (the National Sustainable Agriculture Information Services)
Xerces Society, Pollination Conservation, Publications
(free download of book, “Farming for Bees”)
Suggested Plants for Native Bees
Adapted from the National Sustainable Agriculture Information Services:
The following is a guide for planting flowers, trees and shrubs to attract native bees. Remember, unlike honeybees, native bees don’t fly great distances from their nests to forage, so these plantings should be within 200 yards of the target crop.
Shrubs and Trees