Could pesticides be limiting the ability of bees to reproduce?
Bees are responsible for pollinating . Eighty percent of all pollination around the world is done by the humble little honeybee. Yet despite bees' primacy in the world agricultural web, scientists are hard pressed to identify a single cause of their rapid and alarming decline.
A recent study by Swiss researchers may help demystify the causes of the decline in world honeybee populations. Scientists have long suspected that pesticides, specifically neonicotinoids, may play a role. Now, researchers say that neonicotinoids could be at the root of the problem, and limiting reproduction.
鈥淢ost neonicotinoid studies that employ honey bees have focused on workers, which are typically the non-reproductive females of the colony,鈥� said lead author Lars Straub of the University of Bern in a press release. 鈥� by honey bee health scientists.鈥�
鈥淲hile not surprising,鈥� Mr. Straub added, 鈥渢hese results may turn a few heads.鈥�
In January, a study found that by 25 percent in Europe since 1996, and 59 percent over the last 58 years in North America. A nationwide survey conducted in the United States between April 2015 and April 2016 found that beekeepers during that twelve-month span.
Research indicates that a number of factors, from climate change to to parasite problems to聽the reduction of biodiversity among the plants that bees visit for pollen, could be in play. Recently, scientists also identified that problems with colonies鈥� mothers, the famous queen bees of pollinator colonies, also contribute to the decline.
"Queen failure is a big problem and this helps explain it," said US Department of Agriculture bee scientist Jeff Pettis of the recent research on bee sperm counts, in an interview with the Associated Press. Dr. Pettis took part in the queen study earlier this year. "It's not the queens themselves, . It's significant."
In the most recent study, researchers found that male drone sperm counts decreased 39 percent in the presence of neonicotinoid pesticides. Bees exposed to neonicotinoid treated pollen produced about 1.2 million living sperm, while bees exposed to pesticide free pollen produced about 1.98 million living sperm.
Thus, while neonicotinoids doesn鈥檛 kill the bees or make them completely sterile, it acts as an insect contraceptive at a time when bees couldn't need it any less.
Queen bees mate with male drone bees during a mating flight during in which the queens stockpile sperm to increase the colony. That single flight is the highlight of the drones鈥� short lives; they die after performing their mating duty.
Bayer Corporation spokesman Jeffrey Donald stated in response to the study that while Bayer, a neonicotinoid producer, would study the problem, laboratory studies are not necessarily indicative of real-world experience. But聽researchers say that the results of this study indicate that there is a need for environmental risk assessments of pesticides containing neonicotinoids.
Pesticides such as neonicotinoids have long been the subject of suspicion among the apiological community, many of whom urge farmers and homeowners to reduce their pesticide use in the face of declining pollinator populations.
While scientists are unwilling to attribute bee colony failure to a single factor, Pettis told the Associated Press that reduced sperm counts could account for as much as a third of the problem.
