Is poor nutrition killing bees?
Bees need a varied diet, experts say.
Sam Hapke, a graduate in entomology at Washington State University, counts bees as part of a research project on a parasite that attacks honeybees.
Poor nutrition could be a major cause of what is known as colony collapse disorder, says bee expert Dr. Gordon Wardell, president of SAFE Research and Development, LLC.
Wardell is working with scientists at the U.S. Department of Agriculture's bee research center in Tucson, Arizona, who are collaborating with Washington State University to pinpoint the causes of serious bee losses in Washington State.
"I think nutrition is one of the significant links in CCD," said Wardell, who has developed a supplemental bee diet called MegaBee under a cooperative research and development agreement with the USDA. "My feeling is that the bees are just dying too early. Honeybee colonies are a series of overlapping generations of bees. The longer the bees live, the greater the overlap, and the more healthy the colony."
Pollen is a source of protein, lipids, and vitamins for the bees, but there are several reasons why bees are not getting a good diet naturally, Wardell said. Studies have shown that higher temperatures, due to global climate change, result in a lower quantity and quality of protein in the pollen of plants.
In addition, increasing use of herbicides such as Roundup (glyphosate) has eliminated weeds from crops and reduced the diversity of the bees' food. Wardell said a hundred times more Roundup is being used in the United States now than was used 20 years ago, partly because of the introduction of Roundup Ready crops such as corn and soybeans.
"We're asking our bees to live on monocultural pollens month after month."
That would be like asking a person to live on nothing but steak for one month, Twinkies for the next, lettuce for the next month, and tomatoes for the next, he said. "Bees evolved on diversity, but they're not getting the diversity in today's commercial agriculture."
If the worker bees die early, because of poor nutrition, that leads to a shortage of food in the colony, and the young bees have to take their place as foragers, he said. "The young bees are physiologically not ready to do that kind of work but are forced to work in the field, and it has a cascading effect."
Dr. Gloria DeGrandi-Hoffman, research leader at the Tucson bee research center, said when she heard of the losses that Yakima, Washington, beekeeper Eric Olson had sustained during cranberry pollination a year ago, she saw it as an opportunity for the scientists to work with his bees to study the nutritional aspects of the problem.
Olson takes his bees to California each November to overwinter in holding yards. They then pollinate almonds in early spring before being trucked back north to pollinate tree fruits. During the summer, they have to be moved to other areas where there are food sources so that the hives are strong going into the winter.
After tree fruit pollination, a third of Olson's bees are moved to canola and other seed crops in the Columbia Basin; another third go to North Dakota to forage on alfalfa and clover in Conservation Reserve Program ground; and the other third go to western Washington to pollinate cranberries and other berries. After the berries are no longer blooming, Olson moves the bees into clear-cut areas in mountain forests to forage on fireweed.
After last winter, he had lost only 7 percent of the bees that were in central Washington for the summer, which he considers a remarkably low number. He lost 13 percent of his bees that had been in North Dakota. But he lost 80 percent of the bees that had spent the summer in western Washington, and the remaining 20 percent were not well. He estimates that overall, 90 percent of all the commercial bees that were in western Washington in 2007 were lost.
This year, Olson dedicated 144 bee colonies to the bee research center's nutrition studies. The colonies were given a variety of nutritional supplements before going into cranberry pollination. All the colonies had candy boards, which is Olson's standard treatment. The boards are covered with a hard sugar and placed in the top of the colonies. In addition, some colonies received one of two different protein treatments, and some just received syrup.
DeGrandi-Hoffman said it is very stressful for bees to pollinate cranberries because the weather is usually cool and wet, preventing them from foraging at times. The scientists are studying the nutritional value of cranberry pollen and also looking at how much pollen the bees pick up from other plants during cranberry pollination. Even if bees collect a large amount of cranberry pollen, they could be nutritionally compromised if there is not enough diversity of pollen, DeGrandi-Hoffman said.
The researchers checked the colonies on their return from western Washington in September and will continue to monitor them until they go into almond pollination next spring.
"We wanted to follow colonies and test the effects of supplemental feeding in a crop that we knew was very stressful to bees," DeGrandi-Hoffman said. "We're looking at how improved nutrition can perhaps prevent, or at least mitigate, the impact of some of these problems like pathogens and mites that are out there. Maybe just through better nutrition, we can prevent a lot of colony losses."
Meanwhile, the scientists are doing studies with caged bees in Tucson, using cranberry pollen collected in Washington. They know the age of the caged bees and can look at the impact of the same treatments used in the field in terms of the protein levels in the bees. The protein and lipid levels in bees have a lot to do with their longevity and when they transition from nurse bees to foragers, which ultimately influences population growth and colony survival, DeGrandi-Hoffman said.
Wardell said it's likely there's nothing wrong with cranberry pollen, but it's not a balanced diet by itself—just as a human diet of steak needs to be balanced with vegetables.
"My whole effort in this nutrition work is to take a lot of the guessing and conjecture out of what we're doing with our bees, and base it on good, sound data," he said.