Parasites, pesticides killing off honeybees

February 21, 2013 

Honeybees in this country are disappearing at a frightening rate because of a problem called colony collapse disorder, or CCD.

One-third of honeybees are lost each year in Washington and around the country.

This should scare you, especially if you like to eat. The USDA Agricultural Research Service estimates that bee pollination is responsible, directly or indirectly, for one out of every three mouthfuls of food in our diet. Many of the commercial tree fruit, berry, nut and vegetable crops grown in the U.S. are dependent on honeybee pollination.

When the CCD noted the collapse, beekeepers initially blamed pesticide use. Many of our commercial and garden pesticides are toxic to bees. Farmers and gardeners have been cautioned about using pesticides when bees could be present and and urged to use chemicals only when necessary. However, the problem has turned out to be more complex and research is being conducted to determine the possible causes of the CCD.

Early research associated CCD with the presence of Varroa mites, virus transmitting parasites often found in hives decimated by the collapse disorder. Further research indicated that multiple factors may be at fault, including a pathogenic gut fungi called Nosema, and other unknown pathogens; Varroa mites; and stress. Some management practices and environmental conditions do influence bee and colony health.

Domesticated honeybees kept in manmade hives can be stressed by overcrowding and from being moved from location to location for pollination of commercial crops. Environmental stresses can include the limited availability of clean water, a scarcity and lack of diversity of pollen and nectar, and low-nutrition pollen and nectar.

Exposure to pesticides also is a factor. This includes the pesticides beekeepers use to treat hives for control of Varroa mites. Insecticides, miticides, fungicides and herbicides that bees are exposed to while foraging build up in the wax of the comb over time. Because of this, experts now recommend that beekeepers change the combs more frequently.

Washington State University takes the problem of CCD seriously. After all, honeybees are essential to most of the fruit and vegetable crops grown in the state. WSU’s Honey Bee Colony Health Diagnostic Laboratory is researching Nosema, the interaction between parasites and pathogens, and the effects of sub-lethal pesticide residues being found in hive combs.

What can gardeners do while researchers try to find the solution to the CCD problem? The Home Garden Seed Association recommends:

1. Plant flowers in clustered clumps at least 4 feet in diameter. They’re more attractive to honeybees and other pollinators.

2. Plant a variety of flowers that bloom at different times, so you’ll have flowers that provide nectar and pollen from spring to fall.

3. Try to manage pest problems without chemicals.

-- Marianne C. Ophardt is a horticulturist for Washington State University Benton County Extension.

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