Honeybee deaths are on the rise and researchers believe the 40-50 percent decline in population is due to pesticides. Honeybees have been dying in masses for several years, but this year the deaths have spiked even more, according to commercial beekeepers.

According to the New York Times, beekeepers have recorded the mysterious disorder, colony collapse disorder, since 2005. Before then, beekeepers, which are transported to farmers who need the honeybees to pollinate their crops, could expect to lose five to 10 percent of their hives. In 2005, that number suddenly swelled to a third. Now, some beekeepers have reported losses of 55 percent.

About 40 to 50 percent of the hives needed to pollinate many of America's fruits and vegetables are gone. So far scientists studying the ailment, called colony collapse disorder, have not been able to find a conclusive explanation.

Dennis vanEngelsdorp, an entomologist at the University of Maryland who is one of the leaders of the survey team, said he can't predict what the past winter's average loss figure will be. The beekeepers' reports are being solicited online for the next two weeks, and the figures are due for release on May 7.

"What I can say is, when we were in California this year, the strength of the colonies that were there was significantly lower than it was in previous years," vanEngelsdorp told NBC News. 

Neonicotinoids, a chemical which can remain in the plan for months, well as another pesticide, coumaphos, have come under fire with a recent study published in the journal Nature Communications. In the laboratory, the researchers exposed bees to the amount of pesticide that would be about equal to what they would receive in the wild. According to the BBC, the pesticides targeted the learning center in bees' brains. The results showed that as many as 30 percent of honeybees were unable to learn or failed memory tests.

"Pollinators perform sophisticated behaviours while foraging that require them to learn and remember floral traits associated with food," Dr. Geraldine Wright, whose own research prompted the Nature Communications study, said to the BBC. "Disruption in this important function has profound implications for honeybee colony survival, because bees that cannot learn will not be able to find food."