The release of scientific reports from two European studies published in Science magazine last week caused a stir. Major newspapers of the nation published articles accepting the studies as proof of worldwide bee disappearance being caused by the neonicotinoid family of insecticides.

Because a British study showed a reduction of bumble bee queen bees after the bees were fed imidacloprid and honeybees exposed to thiamethoxam being disoriented and not returning to the hive in large numbers, the insecticides are being blamed for the worldwide decline in both types of pollinators.

According to a Bayer CropScience environmental toxicologist, the French study overdosed the bees by 20 percent to 30 percent in comparison to real world field exposure levels. At the high levels tested in this study, behavioral effects are expected. As for the bumble bee study, concentrations were probably three to six times above typical field exposure levels. But the same levels in previous tests did not show effects to bumble bee colonies, and these latest results were a surprise.

“Our company and other chemical companies have always been looking at the safety of these products beyond whether we are killing bees or other non-targeted insects. In the field of ecotoxicology, the key regulatory end points are fatality, growth and reproduction. So, we are also looking at whether the colonies are able to reproduce and the growth of individual bees, including larvae, because we are trying to protect all the life stages,” said David Fischer, Bayer CropScience, Ph.D., environmental toxicology and risk assessment.

The Washington Post in its Friday edition ran an article with a lead paragraph that gave credit to the new research about neonicotinoid insecticides as starting to “unravel the mystery of why bees are disappearing in alarming numbers worldwide.” It also claimed the new studies “point to flaws in the way pesticides are evaluated by regulators.”

Bayer CropScience registered some of the first neonicotinoid insecticides following testing that the Environmental Protection Agency accepted as having appropriate pollinator safety, and the company has established a Bee Health Center for research in Europe and another one is being established in North Carolina. For both reasons and because the company hasn’t shied away from answering questions, Bayer CropScience spokespeople are often quoted.

Of course, the Washington Post article by Marc Kaufman, quoted British and French researchers as saying the studies are proof of consequences from non-lethal doses of the insecticides. Fischer was quoted as saying the research as conducted doesn’t really show anything. But the writer found a University of Illinois researcher, May Berenbaum, to suggest that bees are at risk from this family of insecticide.

“The problem with these two new studies is that people are saying they show that neonicotinoids are responsible for the bee colony loss problem or the pollinator decline problem, but they don’t really show that at all,” Fischer said.

“Really, the study in France was not a surprise to us. With the dose level that they tested, we would have expected the kind of effect that they saw. The particular chemical that they used in the test was not a Bayer CropScience product. Thiamethoxam is marketed by a different company,” he noted. “But the study in France tested an exposure that is much higher than the level bees would be exposed to in fields.”

He said he was confident that bees would not have strayed away from the colonies at a lower dose of product used in real agricultural settings because no such effects have been seen in previous field dose studies.

“What they really saw with the study in the UK was an affect several weeks after they stopped feeding the bumble bees imidacloprid. They fed the colonies imidacloprid at 6 to 12 parts per billion in pollen in the laboratory and then moved those colonies out into the field where they foraged nature food, and it was after the imidacloprid feeding stopped that they really saw the main effect, which was a reduction in the production of queens,” Fischer explained.

Fischer suggested this study protocol has not been fully investigated to validate the approach, and it is something that needs to be looked at in more depth. 

The Washington Post article gave no attention to what has been recognized as a major cause of colony health problems—parasitic mites. Varroa mites and disease vectors associated with the mites have been proven to be a main cause of bee deaths and colony collapse. “Those are the main problems causing health problems in honeybees, and pesticides either play no role at all or they play a very minor role,” Fischer said.

Bayer CropScience has noted that the neonicotinoid family of insecticides is used extensively in Australia, but varroa mites are not present. The result is that bee health has not been compromised in that country from the use of the insecticides.

“In my mind, it seems in some cases that the insecticide work done is overshadowing what we know to be a real threat to bee health, and that is varroa mites,” said Jack Boyne, Ph.D., director of communications, Bayer CropScience.