Despite dramatic losses in wild honeybees and in colonies maintained by hobbyist beekeepers, Cornell University apiculturists say the pollination needs of commercial agriculture in the United States are being met -- for now -- by commercial beekeepers, although their supplies are precarious.

"Parasitic mite and mite-related diseases have caused the death of most wild honeybees, and left the commercial colonies at tremendous risk," said Nicholas W. Calderone, head of the university's Dyce Laboratory for Honey Bee Studies and an assistant professor of entomology in the College of Agriculture and Life Sciences at Cornell. Calling the Varroa mite "the greatest threat to beekeeping," Calderone said beekeepers have only one registered chemical (Apistan) to control Varroa mites, "and European mites have already become resistant to that chemical, so we must assume the same thing will happen in the U.S."

Roger A. Morse, the recently retired Cornell professor of apiculture who tracked the mites and diseases for 25 years, concurs. "The mites represent the greatest threat to beekeeping since European bees were brought to this continent more than three centuries ago," Morse said. "But if we can get the results of research to the beekeepers, we can keep the crops growing and the honey flowing.

"It's true that these mite diseases have caused the death of 95 to 98 percent of the wild honeybee colonies. And more than half the hobby beekeepers have lost all or most of their colonies," Morse reported. "However, commercial beekeepers in this country are surviving, though they, too, have had serious losses. Research on the biology and control of bee diseases is making it possible for the industry to cope and provide the 1.2 million colonies needed for the pollination of crops we eat."

Some 90 different crops -- ranging from apples to zucchini and cantaloupes to cucumbers -- depend on honeybee pollination. To some extent, other insects will pollinate specific crops. However, no insect is as widely effective as the honeybee, and with the disease losses among wild and hobbyist honeybees, the commercial honeybees are more important than ever, Morse observed. The value added by honeybee pollination to American agriculture is estimated to range from $5 billion to $20 billion a year, he said.

Crop pollination is a migratory enterprise, with honeybees following seasonal crops -- week by week -- as trees and other plants bloom. Many commercial beekeepers' bees winter in Florida and travel on trucks that hold up to 500 colonies and 10 million to 15 million pollinators. Commercial beekeepers place their colonies near crops that need pollinating and charge growers for the service. Migratory beekeepers also sell the honey and other bee products that result, but fees for pollination services are their main source of income.

"We need to sustain a significant research effort to protect the safe and affordable supply of fruits and vegetables to which people have become accustomed," Calderone said. "Mites are living organisms, and mite populations will eventually adapt to whatever control measures we develop. It is an ongoing struggle that can never be completely won."

So research efforts at Cornell and other institutions are focusing on the biology of the Varroa mite, trying to understand how it locates bees in the first place. "If we can determine the host-location mechanism and discover the physical and chemical cues the mites use, we may be able to manipulate those cues for a control mechanism that will protect the bees," Calderone said. A number of natural products, including essential oils from herbs and spices, also are being examined for their potential in mite control, he added.

But a genetic solution -- breeding bees that are resistant to mites -- will be much more difficult, Calderone predicted. Even if beekeepers start with disease-resistant stock, it is almost impossible to control mating (with non-resistant males) when new queens leave the colonies, he explained. "Commercially viable, disease-resistant stock is the best answer, but that is years away, at best," Calderone said. 'Nonetheless, it remains the long-term focus of several research programs around the country."

Meanwhile, commercial beekeepers are surviving by applying good management techniques in their craft, Morse said. Dead colonies are replaced when beekeepers "split" their surviving colonies each year to maintain the stock needed for pollination.

"Growers who rent bees are well aware of the problems and are making plans with beekeepers for the colonies they will need for next spring's pollination," Morse said. "At the same time, there continues to be a great interest in hobby beekeeping, and hobbyists also are learning to cope with mites and diseases by tapping into resources like Cornell's apiculture extension program."