Natural History: Trouble with honeybees - includes related article on why North American Indians call honeybees the white man's fly

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Trouble with honeybees - includes related article on why North American Indians call honeybees the white man's fly

Sue Hubbell

Last year, parasitic mites and harsh winter weather eliminated 80 percent of the honeybee colonies in some parts of the country.

When European settlers arrived on the shores of North America in the seventeenth century and discovered to their dismay that there were no honeybees here, they set about importing them. Never mind that more than 3,500 species of native bees were buzzing about, energetically pollinating the native plants and the few crops--including squash and beans--grown by the people the settlers called Indians. Those bees do not produce useful amounts of wax or honey. Only honeybees do that, and without them the settlers lacked good-quality wax with which to make candles to light their dark days and darker nights and had to make do with myrtle wax or tallow from beef or deer. Without honeybees, they also lacked the major ingredient of mead, an alcoholic drink made from fermented honey and water. And last of all, they had no honey to sweeten their food.

The early settlers weren't interested in the pollination work that the native bees--or even honeybees--could do because they weren't aware of it. The role of insects in botanical fertilization was not clearly known until the late 1700s, long after the first recorded importation of European honeybees (Apis mellifera) to this continent. That report appears in a letter dated 1621 and written in the English office of the Virginia Company: "wee have by this shippe sent . . . fruit trees, as also pigeons . . . and bee hives . . . the preservation and increase hereof wee recommend unto you." If these bees survived the ocean voyage (of which there is no record), they would have prospered in Virginia and could have been the origin of swarms that spread westward in the following years. Sometime between 1630 and 1663, honeybees were also brought to New England to brighten the lives of colonials there.

By 1800, swarming feral honeybees, nesting in tree hollows, had reached the Mississippi. In the 1850s, the bees were brought by ship to the West Coast, where their population was soon increased by bees carried overland by settlers, who kept them in cramped hives inside hollow logs. During the next half century, with the invention of better beekeeping equipment and the development of an industry to manufacture and sell it, honeybees, both feral and cared-for, were to be found throughout the United States.

Once the honeybees' role in pollination had been added to the list of their known virtues, farmers began setting out hives in orchards to increase fruit yield. But it wasn't until the present century, as agribusiness transformed farming in many parts of the country, that honeybee pollination services became a business as well. Tractors powered by internal combustion engines (already in use by the late 1800s) and the caterpillar tread (used in World War I tanks) may have given large-scale agriculture a push. The shortage of men to do heavy hand labor during World War II, the design of ever-more sophisticated farm machinery, and the development of pesticides all contributed to dramatic changes in American agriculture. Farms became bigger, and machines took over much of the hard labor. Large plantings of single crops--monoculture--became the rule.

Beekeepers learned to take advantage of both mechanization and the growing agricultural need for pollination, and once again, the bee of choice was the honeybee. Many crops, especially those cultivated on a large scale--such as alfalfa and oranges--are not native to North America and may have bloom times that are more in sync with the population peaks of the introduced honeybee than with those of native species. In addition, most native bees fly no farther than 100 to 200 yards from their nests and have solitary nesting habits that make them harder to manage.

Grouping four or five hives of honeybees on a pallet, modern beekeepers use forklifts and boom loaders to load and unload pallets from trailers, truck them from place to place as different crops come into bloom, and move on before the fields are sprayed with insecticides. The fee they receive for this service has become a more important source of income for some beekeepers than has honey. In recent decades, another, easily managed exotic bee--the alfalfa leaf-cutter bee--has come to play a significant role in commercial pollination, particularly of alfalfa. Together these two introduced bees account for about 90 percent of agribusiness crop pollination in the United States.

But now, the honeybees on which we have become so dependent are in trouble. In the spring of 1996, almond growers in California were advertising that they would pay $34 per colony for beekeepers to bring honeybees to their trees. This is up from the $22 per colony that beekeepers were charging in the 1980s. In Maine, it was hard to find honeybees at any price last year.

Like all animals, honeybees get sick and have parasites, but over the years, beekeepers had learned how to help their bees stay healthy. Once a disease or pest takes hold in any large population, however, it can spread rapidly. In the last fifteen years, two particularly devastating species of parasitic mites have shown up in American hives. One, Varroa jacobsoni, parasitizes bee larvae; the other, Acarapis wood), infests the trachea of adult bees. Treatments have been far from perfect; 15 jacobsoni has begun to show resistance to the chemical American beekeepers have been using to fight it and breeders have so far failed to develop a totally mite-resistant bee.

Rough estimates suggest that last year the mites, together with harsh winter weather, may have eliminated 80 percent of the honeybee colonies in some parts of the country. In the part of the Ozarks where I kept bees for twenty-five years, only a few hives, and apparently no feral honeybees, survive. Ten or twelve years ago, it was the rule of thumb in this part of southern Missouri that there were approximately as many feral honeybees--living in tree holes and under the sides of abandoned buildings--as hived ones, and that the feral bees, along with native bees, were doing a lot of pollination for free.

In Missouri, where farming is a matter of raising cattle, a nice stand of white clover in a pasture is appreciated. There are also a few orchards in the state. Today, farmers tell me that their white clover and fruit are the poorer for the lack of honeybees. In talking to other beekeepers and researchers around the United States, I frequently hear the same story. Many beekeepers, discouraged by the expense of replenishing their stocks of bees each spring and the growing inutility of antimite treatments, are leaving the business.

The picture is not completely bleak, however. Scientists are working hard to understand the life cycles of the parasitic mites and to develop mite repellents and pesticides. Some biologists are hopeful that bee behavior can be brought into play--perhaps bees can be bred that will get rid of the mites by grooming one another or by removing infected pupae from the colony. A series of mild winters might also help the bees survive future mite attacks.

Meanwhile, researchers are beginning to take considerable interest in both our native bees and a handful of species imported as crop pollinators. Now there is a fledgling industry in these bees--called pollen bees to distinguish them from honeybees.

Unlike the social honeybees and, to a lesser extent, bumblebees, which nest in large colonies and divide themselves up into castes, each with a different job to do, most of North American native pollen bees are solitary. Each mated female solitary bee makes her own nest--with about ten brood cells--in a hole in the ground or, depending on the species, in a stem, post, or rotting tree. She builds her nest brood cell by brood cell, provisioning each cell with a mixture of nectar and pollen, laying a single egg in it, and then sealing it off before moving on to make the next one.

Solitary bees range widely in size: the smallest North American species, Perdita minima, is about the size of a fruit fly typical carpenter bees may reach an inch and a half in body length. Many are generalists; some are specialists: squash bees, a species of miner bee, work American native gourds; another kind of miner bee prefers wild morning glories; an oil bee of the genus Macropis loves the oil of lysimachia, wild yellow loosestrife (oil bees mix plant oils, not nectar, with pollen for their young); and some nightflying sweat bees pollinate evening primroses.

One question of interest to many researchers today is how the native pollen bees may have been affected by human activities--especially those associated with agriculture--and by competition with the honeybees. I asked Charles Michener, of the University of Kansas, the grand old man of American bee and pollen studies, what he thought. "Well," he said, "disturbed land and bare ground created by humans are better for wild bees than undisturbed, wooded land. Bees like open, sunny places." Michener added that in 1983, some of his students compared disturbed land near Lawrence, Kansas, with pristine areas nearby and found not only more individual bees on the former but also more species of bees. And he cited an unpublished 1972 study by the Illinois Natural History Survey, which found the same 220 species of bees living in an area near Carlinville, Illinois, that had been there in the early 1900s. Michener cautions, however, that this was a study of a single, small area, and that the original data were collected long after the introduction of honeybees. He also makes the point that it is difficult to come up with an accurate assessment of the effect that humans and imported honeybees have had on native species without a census of the number and diversity of bees before settlers arrived. "Very little work on this important matter has been done, except in Australia," he said. "David Roubik also has some data from South America."

The Australian work, I discovered, suggests that honeybees, which were introduced to that continent 150 years ago, may displace native pollinators--birds as well as bees--from flowers. Honeyeaters, for example, birds with long, slender bills, visited flowers less often when honeybees were active and tended to concentrate on those flowers least used by the honeybees. Meanwhile, some studies suggest that the introduced honeybees do not always pollinate native plants effectively, which may lead to the production of fewer fruits.

I reached David Roubik at his office in Panama, where he is a scientist with the Smithsonian Tropical Research Institute. "I've studied bees in Mexico, Panama, and French Guiana," he told me, "and have good data on the population dynamics of native bees for seventeen years." The situation is complicated in the Tropics by the presence of native bees that, like honeybees, produce and store honey. There are also hundreds of thousands of flowers for the' bees to visit. Roubik suggests that the honeybees may be able to outcompete the native bees (both honey producing and solitary) because they forage over greater distances and, if necessary, can move their colonies. Roubik adds, "It is interesting to note that there are fewer bee genera in the Old World, where honeybees have been for a long time, than in the New World, where they have been for only a short time."

Suzanne Batra, bee scientist with the U.S. Department of Agriculture, offers a different explanation: "I think the different number of genera reflects past climatic differences. While it is reasonable to think that exotic honeybees will compete for pollen and nectar with native species, there are as yet no hard data, and I am not convinced that competition is as important as some people think it is." I visit [ILLEGIBLE TEXT] vibrant woman with her hair in a single long braid, at her office in Beltsville, Maryland. A field biologist with much experience studying pollen bees in Asia, where several native species of honeybees are abundant, she is impatient at being held inside on rainy day Her room is a zestful clutter of files, magazines, technical papers, cartoons, and photographs. Stacked papers threaten to swamp the postage-stamp-size open space on her desk. From one stack, she pulls out a diagram from a population study on a wide variety of species of East Coast pollen bees and shows me that their numbers are high very early in the springtime, when they emerge, mate, provision their nests, and lay their eggs. The adult population plunges by late May, just as the dense forest canopy leafs out, most forest flowers finish blooming, and honeybee numbers are building, indicating that they do not feed on the same flowers. Currently, Batra is working with a species of ground-nesting Andrena bees that are important pollinators of red maples, pear trees, and early-blooming wildflowers. These native bees are so tolerant of the cold that they emerge from their nests as the snow melts in February, long before other, warmth-loving bees are able to fly.

Further evidence that native bees can hold their own against honeybees comes from random samples Batra and Edward Barrows, of Georgetown University, took in some West Virginia woods in 1991. The year's catch turned up only 34 honeybees and 1,701 native pollen bees. The proportions were similar in 1992 and 1993 catches. Recently, Batra has also taken random. samples near her laboratory in Maryland, where there are numerous, healthy honeybee hives (part of the Department of Agriculture's research on the troublesome, mites). Even there, of the bees caught in sweeps around, fruit trees and blooming wildflowers, only about 10 percent are honeybees; the rest are all pollen bees.

Batra points out, however, that native bees in other environments may be more vulnerable to competition with honeybees if they are more abundant. One experimental study in Arizona, conducted by ecologist William Schaffer and entomologist Stephen Buchmann, both of the University of Arizona, suggests that honeybees can have a significant, adverse effect on native pollinators of shindagger, a native species of century plant.

Until more data are in, Batra, for one, does not see cause for undue alarm on the subject of honeybee--native bee competition. She also agrees with Michener that humans have made good habitat for native bees by clearing the land and opening up the dense forests that originally covered much of eastern and central North America. In addition, crops and ornamental plants in medium-size clearings and meadows have given the bees new so trees of food. But, she adds, some agricultural practices, especially those associated with large-scale agribusiness--such as the elimination of hedgerows, irrigation (which floods the cells of ground-nesting bees), and the use of insecticides--may prove harmful to our native bees. "Some species have benefited from us; some have not," she concludes.

Batra hopes that the more that researchers and farmers learn about pollen bees--native and imported--the more they will want to employ them, and that with greater commercial use may come changes in agricultural practices beneficial to the bees. She shows me the plastic nest boxes now being sold for keeping one familiar pollen, bee--the bumblebee, which sometimes out-pollinates the honeybee ten to one. For some crops, such as red clover, bumblebees are the most important pollinator. The nectar-bearing part of the red clover blossom is too deep for a honeybee's tongue; the bigger bumblebees have longer tongues and happily apply themselves to the blooms. Several challenges remain, however, before bumblebee pollination can become commercially economical outside of the greenhouse. Bumblebee colonies do not endure from year to year; they are tricky to raise artificially and, although costs are coming down, currently expensive for farmers to bring to their fields.

At last the rain breaks, and Batra takes me outside to show me a few of the other species that show promise as agricultural pollinators. Some, like the shaggy fuzzyfoot bees nesting in dry adobe blocks near her lab, are imported. About the size of honeybees but fatter and darker, these Japanese bees (Anthopora pilipes villosula) are active and fast flyers on this cool, gloomy day, which is too inclement for honeybees and native bees. Nearby, Batra and I look at nest setups for some other species: drilled slabs of wood, looking like giant cribbage boards, for alfalfa leaf-cutter bees; bent cardboard tubes for a variety of mason bees. Then we walk down a woodland path to see the ground nests of what Batra has named polyester bees. To keep their brood cells from getting damp, the three species of native polyester bees nesting in the sandy soil beside the path waterproof their cells with a thin transparent film, made from polyester, which they secrete from a gland in the abdomen. The weather today has kept these bees inside their closely grouped nests, but a few have been at work carrying grains of sand to the surface and arranging them around their holes. When we return to her office, Batra shows me a liner she excavated from a polyester bee cell. With an extra flap on the top, with which the female closes the cell after she has laid her egg, the transparent liner looks for all the world like a Ziploc bag.

The polyester and other native ground-nesting bees contribute greatly to the pollination of both wild plants and crops grown on small farms and in home gardens, but they are difficult to manage on the scale required by agribusiness. They can seldom be attracted to artificial nesting spots, and it would require a great deal of hand labor to go about with a shovel digging up their nests. But research goes on, with some notable successes. Growers, for example, have managed to establish beds of a special soil that is acceptable to the ground-nesting alkali bee, which is sometimes used for alfalfa pollination in the West. Unfortunately, their success has led to new problems: the unnaturally dense populations of alkali bees nesting in these beds have proved especially vulnerable to their natural enemies, which include fungi, other microorganisms, and parasitic insects.

Partly because of the difficulties of "domesticating" our native solitary bees, Batra sometimes chafes under the recent regulatory climate that restricts her experiments with selected, manageable, imported pollen bees. Some scientists, worried about possible negative effects of introduced bees on native species, would like to see the research limited to native species. Batra's work is to develop a stable of bees that are inexpensive and easy to manage, and she suspects that some of the best candidates may come from other countries, where our major agricultural crops come from as well. "Some people have a prejudice against exotics," she says. "It is an anti-immigrant feeling. But, after all, most of our crops, livestock, and we ourselves are exotics, and honeybees were also imported. I think there is a need, and room, for many kinds of helpful bees."