Humming Praises for the Wild Bee
The New York Times
By ANNE RAVER
April 24, 2008
I’VE been watching the bumblebees flying around the kitchen porch of our old farmhouse in Maryland, and wondering if they have a nest nearby, maybe under the eaves. They like shady spots, protected from the wind and the rain. There are probably some mason bees, too, holed up in the old boards of the barn, or in holes drilled by wood beetles in the trunks of dead trees.
The bumblebee and other native wild bees are all the more important in the garden now that the population of honeybees is in such decline — down to 2.4 million colonies last year from 5.5 million in 1945, according to the Department of Agriculture, due mainly, scientists say, to mites infesting the hives and, lately, to a mysterious epidemic called colony collapse disorder.
Native bees pollinate everything from pear and cherry trees to blueberries, tomatoes and eggplant. They are also fascinating to watch.
So the next time a bumblebee buzzes around your head, don’t swat at it. Follow it around. You might see it mating, or gathering nectar and pollen and flying off to its nest.
There are more than 4,000 species of native bees, according to “The Status of Pollinators in North America,” a 2007 report by the National Research Council in Washington.
Their total numbers are difficult to estimate because native bees are “hard to identify — they’re small, they fly under people’s radar,” said Scott Black, an entomologist and the executive director of the Xerces Society, an organization that studies insects.
But native bees are on the decline too and we need to encourage them, now that there are fewer honeybees. (The society has compared field studies from the 1950s through the 1970s with more recent studies, he said, and found “drastic decline” in at least three species of bumblebees: the Western bumblebee, the rusty-patched bumblebee and the yellow-banded bumblebee.)
The European honeybee, Apis mellifera, was brought here by the colonists in the early 1600s to make honey, said Tristram Seidler, the staff ecologist for the New England Wild Flower Society. “Its pollination service was only recognized later on,” he said.
Until then, from the time the first flowering plant was pollinated by a bee 120 million years ago, native bees had been doing the job just fine. In fact, Mr. Seidler said, they are at least 10 times more efficient than honeybees.
“They visit more plants per hour, at a fast speed, and make pollen more available,” he said.
Native bees fly farther between flowers, thus doing a better job at cross-pollinating than do honeybees.
And honeybees are at a disadvantage when it comes to certain flowers, like the blueberry. “Its petals are joined, with a very small opening, so the bee can’t even force himself inside,” Mr. Seidler said. “That’s why buzz pollination” — the bumblebee’s specialty — “is more effective.”
Buzz pollination is a process that sounds very nice for both flower and bee: Bumblebees and some other native bees “use their flight muscles to vibrate the flower until the pollen is shaken loose,” Mr. Seidler said. Like honeybees, they use their middle pair of legs to gather the pollen into pollen sacks. “You can see these on bees when they’re flying by.”
Sometimes they sit on the flower and vibrate; sometimes they hang upside down and do their thing. And when they fly off to other flowers, some of that pollen just naturally falls off and pollinates the plants.
Mason bees don’t have pollen sacks. “They have rows of stiff hairs on their lower abdomens,” Mr. Seidler said. “They use their legs to pack the pollen into those hairs, so that when they’re crawling around on other flowers, the sticky stigmas will get the pollen.”
That makes them better pollinators than honeybees, he said, because they are small and can really get down into those flowers.
Honeybees, however, build large colonies of 20,000 to 100,000 bees, so they have the numbers to pollinate huge commercial orchards or fields of tomatoes or strawberries. So growers have long rented them from commercial beekeepers, who truck in their hives, much like migrant workers, to pollinate the flowers when they open. When the job is done, they haul them out again, and the growers can spray the crops without harming the bees, which are sensitive to pesticides.
But now growers have an economic incentive to reduce their pesticide use — to help encourage the native bees in their area, which are not, of course, trucked in and out of their habitat.
“We do think that pesticides could very well be one of the stress factors on the honeybee,” said Dennis vanEngelsdorp, the acting state apiarist with the Pennsylvania Department of Agriculture. But as with habitat loss, another logical stress factor, it is difficult to prove a direct connection.
Growers are also planting long strips of native plants, like lupine, poppies and goldenrod, to feed the native bees and help them flourish.
Gardeners can do the same thing, in backyards and terraces.
“You need to have continuous blooming, especially in early spring and late fall,” Mr. Seidler said. “Plant natives with a mix of flower shapes to accommodate a variety of pollinators.”
Different native bees have different life cycles, some only a few weeks long, which is why a mix of plants that bloom from spring through fall will keep a variety of bee species well fed.
There are a few basic tenets for the bee gardener to keep in mind: First, limit the use of pesticides, or stop using them altogether. That includes spraying the lawn with herbicides.
Provide a source of water and clay because mason bees build their nests with mud.
“You don’t need much,” Mr. Seidler said. “Dig a tiny hole — a couple shovelfuls of clay soil — and add water every couple days. They’ll find it if it’s there.” If you have no clay soil, go to an art supply store and buy some potter’s clay.
Some native bees seek out patches of bare ground, especially sandy banks that face south or east, where they can get sun. Others will nest in standing snags or dead trees, if the bark is removed.
They like brush piles too, particularly with hollow-stemmed plants like sumac, teasle or bamboo, which have nodes in the stems that make natural compartments for the bees.
It’s funny what happens when you start paying attention to one thing and it leads to another.
I haven’t found out where those bumblebees outside the kitchen door are nesting. But when I sat down on an old bench in the barn to take off my garden boots, I saw a little black bee crawling into a hole in the wood.
I think it was a mason bee — and I welcomed her.
Care and Feeding of Local Bees
You can help native bees by building them shelters. Bundle sticks of sumac and bamboo, with the open ends all going one way and the closed ends going the other. Then place the bundle where it is sheltered from the rain.
To make houses for mason bees, drill holes of different sizes in a block of wood. Bumblebee boxes are a bit more complicated: they resemble bird houses, but with a smaller hole, and are filled with some kind of nesting material, like cotton batting. (Instructions for building both nests are www.xerces.com.
Two excellent guides to bee gardening are the Xerces Society’s “Pollinator Conservation Handbook” and “The Wildlife Gardener’s Guide” from the Brooklyn Botanic Garden.
As luck would have it, the plants bees love are pleasing to humans, too: trees and shrubs like dogwoods, sweet pepperbush, elderberries, blueberries and viburnums, especially Viburnum dentatum, V. cassionoides and V. lentago.
Flowers that bees like include monkshood, aster, Indigo, buckwheat, great blue lobelia, blazingstar, lupine, Virginia bluebells, penstemon and salvia.
As for herbs, try anise hyssop, borage, marjoram, oregano and rosemary. Bees will nuzzle some exotics too, especially the old-fashioned single-flowered snapdragons, lavenders, catmints, Russian sage and and speedwell.