NEWCASTLE, England, April 22 (UPI) -- The evidence against neonicotinoids is mounting. Two new studies -- both published this week in the journal Nature -- suggest the popular class of pesticides are decimating bee populations, both managed honeybees and wild bumblebees.
One of the studies, conducted by researchers at Newcastle University, showed that bee populations can become addicted to pesticides, just as people can come addicted to chemicals like nicotine. Experiments demonstrated that bees, given the choice between different food sources, prefer sugar solutions laced with the pesticides imidacloprid and thiamethoxam.
Like the human urge to smoke cigarettes, researchers say a bee's preference for toxic nutrients is detrimental to its health. Numerous previous studies have linked pesticides to declining bee health and shrinking bee populations.
"If foraging bees prefer to collect nectar containing neonicotinoids, this could have a knock-on negative impact on whole colonies and on bee populations," Geraldine Wright, lead study author and researcher at the Institute of Neuroscience at Newcastle University, said in a press release.
Another study -- this one a field study by researchers at Sweden's Lund University -- found that bees were negatively affected by the presence of pesticides.
Researchers monitored the health and behavior of bees in two newly grown fields -- one grown with seeds treated with a neonicotinoid insecticide called clothianidin, and another untreated.
While no effects on honeybees were observed, the health, reproduction and distribution of wild bees was found to be negatively affected by the pesticide.
"We saw a clear negative impact on growth and ability to reproduce in bumblebee colonies near treated rapeseed fields," lead researcher Maj Rundlof said in a press release.
Even if honeybees are able to cope with the presence of clothianidin in the short term, they may ultimately be negatively affected. Not only have pesticides been shown to directly harm bees, they also make the pollinators more vulnerable to disease. Previous research has shown those diseases can travel from wild bee populations to honeybee colonies, and vice versa.