News of a 30 percent loss of bee colonies last winter raised alarm about the state of these important pollinators. Important as they are for the production of much of our food, the public knows surprisingly little about bees. Annual losses of 20 to 30 percent have been the norm since varroa mites were introduced in the 1980s. This is just one unfortunate event in the long history of bees and people, which is checkered with well-documented episodic losses of bees from disease and human enterprise. One thing is clear: without knowledge of bees’ history and the influence of the hive environment, we cannot accurately identify threats to bee health.
The European honeybee was brought to the United States by colonists and thrived. The industrial revolution of the 18th century introduced major challenges that bees face to this day: exposure to toxic pollutants, urban sprawl, less rural forage, and more recently, invasions of new pests and diseases.
Pesticides pose problems to bees but not all chemicals are equally harmful. The current media and environmentalist focus singles out a new class of pesticides known as neonicotinoids. Little understood is the fact that these innovative “seed treatments” represent a major advance over the pesticides that have been used in the past, which will be used again if the activists have their way and manage to get them banned.
How pesticides are applied matters as well. For example, around 1920, the advent of cheap calcium arsenate dust applied by airplane expanded the amount of land that could be covered and with it the number of bee colonies lost. At the same time, bee kills from industrial sources like smelters were recognized.
DDT, introduced in 1946, represented the first of the new synthetic organic insecticides and was broadly applied until the chemical was banned in 1972. DDT substitutes; carbaryl, organo-phosphates, and encapsulated pesticides caused far more severe bee losses. Pyrethroids offered bees some relief, since some formulations were repellant. Insecticide kills became so severe that from the 1960’s through 1977, the federal government had a pesticide indemnity program to reimburse beekeepers and prevent bee kills from driving them out of business. How bad were these losses? Estimated national loss from poisoning was as high as 500,000 colonies. Washington State reported that 66-79 percent of all honeybee colonies in the state received at least one kill from pesticides every year over a three-year period. California beekeepers lost an average of more than 60,000 bee colonies a year.
Compare that to today. In all of Canada, from 2007 to 2012, there were a total of 110 pesticide incidents, 75 percent of which were classified by Health Canada as minor. Over 90 perent of all neonicotinoid incidents fell into this category. Incidents classified as having moderate to major impacts affected an estimated total of 4,257 bee colonies. Of these moderate-major incidents, only about ten percent were attributed to modern neonicotinoid pesticides — and these were mostly issues that could have been mitigated by better practices. The other 90 percent were attributed to older generation of pesticides and miticides used by beekeepers to control varroa mites.
In the United States, recent hive analyses have identified miticides used by beekeepers as the most common and highest concentration of pesticides inside beehives. The impact of these is mostly unknown.
Long-term hive contamination is a continuing problem for honeybees. Many chemicals are soluble in wax. They migrate from nectar, pollen and dust particles into the comb where they can remain for years. Pesticide poisoning is only part of the toxic environment to which bees are exposed. Even some plants are poisonous. Foraging honeybees contact a wide array of harmful environmental pollutants that are often taken back to the hive. These xenobiotics can induce lethal and sublethal effects. Our work on volatile and semi-volatile organic compounds in beehive atmospheres revealed over 200 chemicals, including fossil fuel constituents, industrial solvents, and explosives in addition to pesticides. What most researchers and the public miss is the significant and often dominant presence of these airborne contaminants inside beehives. In other words, it’s a messy world inside the beehive and pesticides aren’t the only toxic materials.
Increased risk from disease is possibly as great a threat as toxic chemicals. Historically, a bacterial disease called foulbrood was the first major cause of widespread, annual bee losses. The invention of moveable frames enabled early detection. Medical treatments provided a means of controlling foulbrood, other than burning of infected hives. But foulbrood plagues were only the beginning. They were followed by indiscriminate pesticide uses in the mid-century. Then, just as the pesticide problem seemed to be subsiding, things again changed. Trucks began hauling bees cross-country for pollination. Hives from all across the United States ended up side by side in orchards where they can share their diseases.