Colony Collapse Disorder and Honeybee Death Linked with Pesticide Use

The ongoing debate about the cause of colony collapse disorder has finally ended. Mongabay recently reported that "Harvard researchers have re-created the mysterious Colony Collapse Disorder (CCD) in several honeybee hives simply by giving them small doses of a popular pesticide, imidacloprid."

Bayer pesticide linked with bee death

Imidacloprid is manufactured by Bayer and the company even released a statement to say that the chemical has no effect on colony collapse. However, the Harvard research conclusively shows that the opposite is true.

The cause for colony collapse has been eluding scientists for many years. However, two studies that came out in Science showed a close link between neonicotinoid pesticides, of which imidacloprid is one. According to Mongabay:

Past research has shown that neonicotinoid pesticides, which target insects' central nervous system, do not instantly kill bees. However, to test the effect of even small amounts of these pesticides on western honeybees (Apis mellifera), Harvard researchers treated 16 hives with different levels of imidacloprid, leaving four hives untreated. After 12 weeks, the bees in all twenty hives—treated and untreated—were alive, though those treated with the highest does of imidacloprid appeared weaker. But by 23 weeks everything had changed: 15 out of the 16 hives (94 percent) treated with imidacloprid underwent classic Colony Collapse Disorder: hives were largely empty with only a few young bees surviving. The adults had simply vanished. The hives that received the highest doses of imidacloprid collapsed first. Meanwhile the five untreated hives were healthy.

Harvard study links pesticide use with colony collapse

Scientists in the past have been cautious about the connection between pesticides and honey bee collapse. However, lead author of the Harvard report, Chensheng (Alex) Lu has dismissed all caution and has made it clear that:

There is no question that neonicotinoids put a huge stress on the survival of honey bees in the environment. The evidence is clear that imidacloprid is likely the culprit for Colony Collapse Disorder via a very unique mechanism that has not been reported until our study.

Beekeepers started feeding bees with high fructose corn syrup and this did not have an effect on bees until 2004-2005 when US corn crop began to be sprayed with imidacloprid. The first recorded outbreak of colony collapse occurred a year later.  According to Lu even, small amounts like 20 ppb of the chemical was enough to lead to full blown CCD within 6 months.

Studies from UK and France support Harvard study's conclusion

Just before the Harvard study was released, two studies from the UK and France also linked neonicotinoid pesticides to CCD. The UK study exposed bumblebees to small doses of imidacloprid and places the bees in an enclosed natural setting. After six weeks, the team found that the nests of the exposed bees weighed less than that the control group. The French team glued microchips to free-ranging honeybees and discovered that the bees that were exposed to pesticide were three times more likely not to return from foraging. This proved that the chemical also interfered with the bees' homing abilities.

Policy change needed to prevent honeybee extinction

Although the pesticide does not kill bees instantly, it does cause colony collapse over time. In fact, it is more dangerous because it does not kill instantly as there is no way of estimating exactly how many bees are affected. Bees are a vital cog in the economy, and the economic value of honeybees in the US alone is said to be $8-12 billion. Policy makers need to now examine the effect of pesticides more carefully and look at long-term effects rather than just short-term to protect the honeybee from extinction.

Image Credit: Honeybee sucking nectar, Severnjc, Wikimedia Commons