Gus Lorenz, associate head of entomology at the University of Arkansas, said his research shows there is little risk to pollinators from neonicotinoid insecticides, including one of its class, the commonly used imidacloprids.
Lorenz said he backs the view of Henry Miller, a biomedical scientists and fellow at the Hoover Institution who argued that the number of commercial bee colonies - and the number of bees - has increased over the last decade since colony collapse disorder was first identified. .
“All the studies show steady increase in bee numbers, here, in Canada and across the world,” Lorenz told Crop Protection News.
Figures from the U.S. Department of Agriculture (USDA) indicate an increase in bee colonies since colony collapse disorder appeared on the radar in 2006. That year, there were 2.4 million colonies, compared to 2.7 million in 2014. These numbers come despite a reported winter death rate of 30 to 40 percent, including 45 percent in 2013, well above the historic rate of around 15 percent.
Researchers at the USDA and elsewhere said the reason the numbers are keeping steady is that beekeepers are working harder, and smarter.
While some studies have blame neonicotinoids for the increased rate in bee deaths, there is an growing body of work that argues the varroa mite, which likely migrated to the United States in the 1980s, is the key culprit.
Dr. Dennis vanEngelsdorp, a University of Maryland entomologist and one of country’s leading experts on honey bees and colony collapses, said the varroa mite is the largest threat to bees.
“We don’t find levels of neonicotinoids that are indicative of widespread exposure or harm,” vanEngelsdorp told Time magazine in April.
Lorenz said he and others began studying the potential effect of the pesticides on honey bees because of the importance of neonicotonoids to farmers and to corn, soy bean and rice, in the Mid-South. Pests such as the extremely hard to control rice water weevil are best managed by the neonocotonoids.
“People started questioning the negative effect of neonicotonoids and we were concerned,” Lorenz said. “We were concerned about this impact and wanted to know the truth, so initiated this study.“
A two-year study of hives in a 2.5-mile radius of acreage treated with neonicotonoids revealed the bees were fine, that the pesticides had little effect. Lorenz conceded crops such as corn, soy bean and rice do not depend on the honey bees for pollination.
A second study introduced sugar water laced with imidacloprids into hives in amounts that should have been lethal. Again, this had little effect on the bees, Lorenz said.
Lorenz believes that some scientists approach the study of honey bees and colony collapse with preconceived notions that pesticides are largely to blame and different studies give different reasons for why that might be the case.
Chronic toxicity was blamed, then it was neonicotonoids that caused the bees to lose their way back to the hive, Lorenz said, adding that the latest study claims the pesticides have impacted reproductive behavior.
A study in Europe, where neonicotonoids are banned, found that male bees, or drones, produced 39 percent less sperm than those not exposed to the pesticides.