Neonic, Bee Link Questioned

OMAHA (DTN) -- Though the European Commission has banned the use of neonicotinoid pesticides on some crops, scientists in the United Kingdom last week concluded data that's available -- so far -- doesn't prove conclusively that the insecticides are playing the lead role in the collapse of bee colonies.

The scientists who conducted a review of available science said research shows bees are exposed to neonicotinoids, but it is difficult to generalize the level of exposure, how they are exposed and what that exposure may have to do with their health.

The published summary led by University of Oxford professor H. Charles J. Godfray, announced the findings of a review of hundreds of studies including many completed since the European Commission banned in December 2013 the use of seeds treated with the neonicotinoid insecticides clothianidin, thiamethoxam and imidacloprid.

In short, a summary published in the journal Royal Society Publishing Proceedings B, http://tinyurl.com/…, indicates more studies are needed to more clearly define the link between the use of neonicotinoids and bee health. The EU ban is up for review this year.

Jeff Donald, external communications for Bayer CropScience, a company that sells neonicotinoid-based products in Europe, said because of the sheer volume of studies done on the issue, it is "important to periodically take a step back and analyze the totality of the research."

Major reviews by independent scientists, he said, have examined research conducted during the past 15 years and concluded the risk of neonicotinoids to bees is "negligible."

"This conclusion was affirmed in a three-year study published this year by scientists associated with the University of Maryland, the USDA and the EPA," Donald said.

"So it is not surprising that after looking at more than 80 studies released over the past 18 months, Professor Godfray found that there is no effect on honeybee colonies from neonicotinoid use, a conclusion in line with what most bee researchers have found over the years."

When contacted by DTN, Syngenta offered the following statement: "This 'restatement' paper is stronger and more balanced. The authors acknowledge what is happening with neonicotinoid insecticides and insect pollinators under field conditions that demonstrate potential real-world exposure, not solely laboratory-dosing experiments.

"Most scientists and pollinator experts agree bee health is affected by multiple factors, including the parasitic Varroa mite, diseases, bacteria, viruses, loss of habitat, poor nutrition, management practices, weather conditions and a lack of genetic diversity in bee populations. Scientific evidence clearly shows that bees and other pollinators can coexist safely with modern agricultural technologies, like neonicotinoids, when product labels are followed."

The UK scientists reviewed new science, including the results of field experiments made public since the ban.

"Evidence continues to accumulate from semi-field experiments that sub-lethal exposure to neonicotinoid insecticides, chiefly but not exclusively at the high end of what is likely to be experienced in the environment, can affect foraging and other behaviors in the field," the scientists said in the review.

"Several true field studies have reported no effect of exposure to neonicotinoid-treated crops on honeybee colony performance, but the first large-scale study of the exposure of bumblebees found strong evidence of harmful effects. There is very little information about the effects of neonicotinoids on non-bee pollinators."

One 12-week study reviewed by the scientists provided "replicate colonies" of honeybees with supplemental pollen paste diets containing imidacloprid at various concentrations. The study found no effect on foraging performance or colony health in the short term, but increasing health concerns in the long term. The study, however, did not suggest neonicotinoids were a sole cause of colony collapse.

Another study examining the day-to-day foraging patterns of 259 bumblebee workers from 40 colonies found them to be affected by individual or combined exposure to the neonicotinoid imidacloprid and the pyrethroid l-cyhalothrin.

"Whereas individual bumblebee foraging efficiency normally improves with experience, this did not occur in individuals exposed to imidacloprid," the scientists' review said. "Evidence was found that the insecticide affected the pollinators' preference for different flowers as sources of pollen."

In another field study, 10 two-hectare plots in Southern Ontario, Canada, were planted with oilseed rape. Half of that was planted with seed treated with the neonicotinoid clothianidin. During peak flowering, four honeybee hives were placed in the center of each field for two weeks before being moved to a site away from insecticide-treated crops.

"Pollen from hives in treated fields had higher concentrations of clothianidin (which were non-zero in controls), but no effects of the insecticide were found for a variety of honeybee colony growth or overwintering metrics," the scientists' review said.

The review provides a number of other summaries about available science including:

-- "New data, data compilations and re-analyses of earlier data continue to show that neonicotinoid residues can be detected in pollen and nectar collected by pollinating bees," the review said. "However, these data are highly variable, making general inference hard. Incidences of high neonicotinoid residues that would almost certainly cause acute toxic effects in honeybees and bumblebees do occur, but not commonly."

-- "Neonicotinoids can be detected in wild pollinators as well as honeybee and bumblebee colonies, but data are relatively few and restricted to a limited number of species," the review said. "Studies to date have found low levels of residues in surveys of honeybees and honeybee products.

"Some information is available on the extent to which pollinators are exposed to neonicotinoids through different pathways in the environment. Most exposure will be at sub-lethal levels from foraging on seed-treated plants, the most important exception being contamination from dust at the time of planting, especially when regulations and best practice are not followed."

-- "Evidence continues to accumulate on the drivers of pollinator decline," the review said. "Analyses of the extinction rates (since 1850) and changes (1921-1950 versus 1983-2012) in species richness and composition of bees and wasps in the UK suggests land use and management changes are the most important historical drivers with major faunal losses occurring early in the 20th century.

"Any effects of changes in pesticide use over recent decades are unlikely to be picked up by these analyses. An analysis of the historical shifts in the ranges of European and North American bumblebees showed that they have failed to track climate warming at their northern range limits, while southern range limits have contracted."

-- "There still remain major gaps in our understanding of how pollinator colony-level (for social bees) and population processes may dampen or amplify the lethal or sub-lethal effects of neonicotinoid exposure and their effects on pollination services," the reviewers concluded, "as well as how farmers might change their agronomic practices in response to restrictions on neonicotinoid use and the resulting positive or negative effects on pollinators and pollination. While these areas continue to be researched, there is still a limited evidence base to guide policymakers on how pollinator populations will be affected by neonicotinoid use or how agriculture will respond to neonicotinoid usage restrictions."

Read the review here: http://tinyurl.com/…

Read the European Commission's resolution to ban neonicotinoids here: http://tinyurl.com/…

Todd Neeley can be reached at todd.neeley@dtn.com

Follow him on Twitter @ToddNeeleyDTN

(PS/AG)

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