Should We Ban the Use of Bee-Killing Pesticides in the United States?


An abandoned honeybee hive after exposure to imidacloprid, a pesticide used in corn. Picture used with permission of Alex Lu.

A recent study by Alex Lu, Associate Professor at Harvard School of Public Health, has linked the use of imidacloprid, a widely used pesticide in commercial agriculture, to honeybee colony collapse disorder (CCD), a condition in which a significant portion of honeybee colonies abandon their hives and the remaining honeybees no longer produce honey or pollinate crops.

Because of this discovery, we will need to reassess and likely ban the use of neonicotinoid pesticides, including imidacloprid, to prevent the total collapse of commercial honeybees in the United States.

Honeybees have been in gradual decline for several decades in the wild, but the sharp decrease in honeybee populations from beekeeping operations first reported in 2006 has surprised many farmers and scientists. Farmers have reported heavy losses in honeybees from dead colonies, ranging from 30% to 90%, which is significantly higher than death from natural causes before this time-period. 

Domesticated honeybees are the only species used for commercial pollination in the United States.  It has been estimated that about one-third of the diet in the United States comes from products pollinated by honeybees alone. However, since the collapse of honeybee populations in 2006, the price per colony has more than doubled.

An abandoned honeybee hive after exposure to imidacloprid, a pesticide used in corn. Picture used with permission of Alex Lu.

Various theories have been proposed for the staggering drop in the population of honeybees, including parasitic infection by mites, fungal and viral infections, and pesticides, but no single cause had been isolated for the collapse in honeybee colonies. According to the United States Department of Agriculture’s “Colony Collapse Disorder Progress Report” from 2010, it was “becoming increasingly clear that no factor alone is responsible for the malady.” 

Some scientists had suspected that neonicotinoid pesticides, which were introduced in 2004 and 2005 for agricultural use in corn, might have been responsible for the sharp decreases in honeybees first reported in 2006. Beekeepers often supply a hive with high-fructose corn syrup after collecting the colony’s honey so that they do not starve in the winter. While beekeeping practices had not changed much over time, it became common practice to treat corn seeds with neonicotinoids to prevent pests from eating them.

Multiple studies had detected residues of neonicotinoids in corn pollen from seeds treated with the chemicals, thus the chemicals remain in the plant far beyond the seedling stage. These findings allowed scientists to hypothesize that the chemicals could travel to any part of the plant, including the kernels used in high-fructose corn syrup, though the levels of neonicotinoids are not monitored frequently in high-fructose syrup.

While concentrations of the chemicals found in the plants are sub-lethal, or not immediately lethal to the honeybees, scientists have raised concern that prolonged exposure to the chemicals could have significant impacts on the health of the honeybees based on the results of other studies, including one from Purdue University earlier this year. However, no experiment has replicated CCD in the field until now, making it the most likely contributor to CCD. 

Lu, the lead scientist of the new study, conducted his experiment in Worcester County in central Massachusetts with funding from Harvard University Center for the Environment. 

In the experiment, the authors administered high-fructose corn syrup with different concentrations of imidacloprid to 16 healthy colonies of honeybees and four additional colonies were not exposed to the imidacloprid. Twenty-three weeks after consuming high-fructose corn syrup with imidacloprid, all but one of the colonies exposed to any concentration of the pesticide had perished, while only one colony not exposed to the pesticide had died.  

Honeybee colonies were exposed to sub-lethal concentrations of imidacloprid and monitored the following 23 weeks.  All but one colony exposed to imidacloprid died, while three colonies not exposed to imidacloprid remain after 23 weeks. Figure used with permission of Alex Lu.

While the evidence has been mounting against the use of bee-killing pesticides in the last few years, most countries have continued using them in agriculture, with the exception of France and Italy. In addition, recent published findings from the United Kingdom and France have contributed evidence against neonicotinoids that complement this experiment.

Pesticides are excellent tools in pest management, and there’s no doubt that we should continue to use them responsibly in our agriculture.  However, all pesticides run the risk of selecting for pests that are resistant to the pesticide until it is no longer useful, as well as killing non-target species.  

In the case of neonicotinoid pesticides, the harm to honeybees is simply too high to continue to use such chemicals. Banning these pesticides would benefit the honeybees, the beekeeping businesses that rely on the well-being of honeybees to make a profit, the farmers that rely on honeybees to pollinate crops efficiently and at a good price, and consumers who eat many of the crops pollinated by honeybees at affordable prices.

There is cause for optimism, because it is likely that banning theses chemicals would have a significant positive effect on honeybees. France and Italy have banned the use of neonicotinoid pesticides and their honeybee populations have started to recover.

There is no doubt that honeybees provide a valuable service that cannot be achieved through other means without substantial cost and lower efficiency in pollinating our crops. Lu has suggested that "we should not wait any longer to take action to safeguard the bee population" and it’s not hard to see why we should implement the ban.

In addition, there should be stronger monitoring of neonicotinoids in the production of high-fructose corn syrup. In response to a question on alternatives to fight pests while keeping honeybees safe, Lu responded by asking the following: “Do you think that there is a need to coat every single corn seed with this pesticide?”

Feeding honeybees with sucrose instead of high-fructose corn syrup has been proposed, but this may not be enough. Lu has pointed out that “the use of imidacloprid is becoming ubiquitous in both agricultural and residential environment, replacing HFCS with sucrose sugar may not be enough to protect bee population.” Only a ban on neonicotinoids would provide a long-term solution to CCD. 

To secure our national food supply and maintain reasonable prices for farmers and consumers, we should be ready to ban the use of bee-killing pesticides if necessary.

The study “In situ replication of honey bee colony collapse” will appear in the June issue of Bulletin of Insectology.