Why are honey bees collapsing?

By Marla Spivak, University of Minnesota Extension

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 one-third fewer fruits and vegetables, and 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. 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. Control has become increasingly difficult because the diseases and mites have developed resistance to some of the treatments.

New treatments are currently available that 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 and beekeepers in the U.S. has been drastically reduced over the last 20 years.

In addition, our environment is not as friendly to bees as it was in the distant past. Urban sprawl has limited the amount of bee “pasture” — flowers such as clover and alfalfa — available to the bees for their food. Pesticides used to kill pest insects on crops 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 move through plant tissue, may contribute to the stress on bees’ immune and detoxification systems. Fortunately, genetically modified crops have no known effects on honey bees.

Finally, the beekeeping heroes who 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, more than one 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. They may become nutritionally stressed, may be at increased risk of pesticide exposure, and are more susceptible to diseases and mites.

But educators and researchers are working on the problem. For more information, visit the University of Minnesota Bee Lab website: www.extension.umn.edu/honeybees.

(Marla Spivak is an entomologist specializing in apiculture with University of Minnesota Extension.)