Why are honey bees collapsing?

Marla Spivak and Gary Reuter, Department of Entomology, University of Minnesota
March 23, 2007

Honey bee colonies in the U.S. are overworked and under-appreciated. They are the world’s most important pollinators of many fruits, vegetables and seed crops, contributing billions of dollars in value to agriculture and our diet. Bees also pollinate wildflowers in our natural ecosystems and much of what we plant in our home gardens. Without honey bees, and other bee pollinators, the produce section in our grocery stores would have about 1/3 fewer fruits and vegetables and it is impossible to estimate how many flowers would not set seed.

Honey bees in the U.S. are maintained by beekeepers, who keep them as a hobby, as a side-line profession, or commercially as a livelihood. All beekeepers harvest honey from their colonies, a wholesome and healthful product. Some harvest other products such as beeswax, pollen, royal jelly, and propolis, which are used to make candles and cosmetics, or serve as nutritional supplements and medicine. Beekeepers keep their colonies of bees in cities, suburbs, and the countryside. Some maintain their colonies in one location year round, and some transport their colonies long distances to follow the blooming plants for honey and to provide pollination service to crops. Some beekeepers propagate “nursery” stock (more bee colonies and queen bees) for sale around the country.

Unfortunately, honey bees are subject to diseases and parasitic mites. The mites were inadvertently introduced into the U.S. in the 1980s. These maladies weaken colonies and can lead to the collapse and death of colonies. Beekeepers are careful to control these pathogens and pests in their colonies, but it has become increasingly difficult because the diseases and mites have developed resistance to some of the treatments. New treatments are currently available which reduce the risk of the pests developing resistance. Fortunately, colonies that die from diseases and mite parasites can be replaced with nursery stock, but overall, the number of bee colonies in the US, and the number of beekeepers, has been drastically reduced over the last 20 years.

In addition to the stress that diseases and mites place on the immune system of bees, our environment is not as friendly to bees as it was in the distant past, which also adds to the overall stress on bees. Urban sprawl and agricultural practices have limited the amount of bee “pasture” (flowers such as clover, alfalfa) available to the bees for their food. The use of pesticides on crops to kill pest insects can have the negative side-effect of killing beneficial insects such as bees. Many pesticide applicators choose pesticides with low residual and low toxicity to bees. But new classes of pesticides, such as those that are systemic (move through plant tissue) may contribute to the stress on bees’ immune and detoxification systems because the pesticide may be incorporated into the pollen and nectar. While we know that pesticides can adversely affect bee health, GMO crops have not been shown to directly affect honey bees.

Finally, the beekeeping heroes that transport their colonies across the nation to pollinate crops for our nation’s food supply face extreme difficulties in supplying bees that are strong and healthy enough for pollination. Often, a large number of bee colonies are required to pollinate a particular crop. For example, over 1 million bee colonies are required to pollinate almonds in California during late February and March. Moving such large numbers of colonies into a relatively small area places even more stress on bees. In these conditions, the bees may become nutritionally stressed, they may be at increased risk of pesticide exposure, and definitely are at increased risk of disease and mite transmission among colonies.

It is no wonder bees are suffering. But the biggest question is: is the collapse of honey bee colonies this year due to yet another factor? Is there a new disease afflicting bees? Are the effects of new classes of pesticides contributing to bee deaths? Why are the bees leaving the colony and not returning? What is the so-called Colony Collapse Disorder? Scientists across the nation are trying to figure this out. At this point, it is unclear why so many bee colonies are dying, and the name Colony Collapse Disorder is a placeholder until its nature can be determined for certain. Most likely, the bees are dying from a number of contributing factors that collectively place an enormous burden on the immune and detoxification systems of bees, eventually "putting them over the edge."

What can you do? Don’t panic. Educate yourself.

If you are a beekeeper, make sure your colonies have adequate pollen and nectar stores at all times. Replace old brood combs with new “foundation” to eliminate disease spores, and sample your colonies for mites regularly so you can control them when needed. Enroll in our on-line course, soon to be available called, "Healthy Bees.'

If you are not a beekeeper, please appreciate the bees in our environment! Spread the word about the benefits of bees. Support research and extension efforts to promote the health of honey bees. Learn to keep bees yourself!

What is the University of Minnesota doing about the problem?

Dr. Marla Spivak, Gary Reuter, and students focus all of their research and extension efforts on keeping bees healthy. They teach several classes to the public, including keeping bees in northern climates, and raising and breeding queen bees. A new on-line course will be available soon that deals exclusively with beekeeping management techniques that can be used to prevent and mitigate disease and mite transmission. The Bee Lab web site has education materials on how to protect bees from pesticides, as well as materials on many general beekeeping practices. The research efforts in Spivak's lab concentrate on breeding bees for "hygienic behavior" - a mechanism of resistance against bee diseases and parasitic mites. They are also researching ways to bolster the immune system of bees. Please take a few minutes to navigate this web site for more information: www.beelab.umn.edu