CATCH THE BUZZ
“Remove The Toxic Talc”, Say Purdue Researchers
Alan Harman
Purdue University scientists are calling for the bee-killing talc being used to aid the planting of corn and soybean seeds coated with neonicotinoid insecticides to be limited or eliminated.
Their research found the insecticides clothianidin and thiamethoxam are present at high concentrations in waste talc is exhausted from farm machinery during planting.
Christian Krupke, associate professor of entomology and Greg Hunt, a professor of behavioral genetics and honeybee specialist, say the talc ends up with extremely high levels of the insecticides - up to about 700,000 times the lethal contact dose for a bee.
“Whatever was on the seed was being exhausted into the environment,” Krupke says.
“This material is so concentrated that even small amounts landing on flowering plants around a field can kill foragers or be transported to the hive in contaminated pollen. This might be why we found these insecticides in pollen that the bees had collected and brought back to their hives.”
Krupke says efforts are needed to limit or eliminate talc emissions during planting.
“That's the first target for corrective action,” he says.
“It stands out as being an enormous source of potential environmental contamination, not just for honeybees, but for any insects living in or near these fields. The fact that these compounds can persist for months or years means that plants growing in these soils can take up these compounds in leaf tissue or pollen.”
Analyses of bees found dead in and around hives from several apiaries over two years in Indiana showed the presence of the neonicotinoid insecticides. Clothianidin and thiamethoxam were also consistently found at low levels in soil - up to two years after treated seed was planted - on nearby dandelion flowers and in corn pollen gathered by the bees, according to the findings released in the journal PLoS One this month.
“We know that these insecticides are highly toxic to bees; we found them in each sample of dead and dying bees,” Krupke says.
Other bees at those hives exhibited tremors, uncoordinated movement and convulsions, all signs of insecticide poisoning.
The neonicotinoid insecticide coatings are sticky and to keep seeds flowing freely in the vacuum systems used in planters they are mixed with talc. Excess talc used in the process is released during planting and in routine planter cleaning procedures.
“Given the rates of corn planting and talc usage, we are blowing large amounts of contaminated talc into the environment,” Krupke says. “The dust is quite light and appears to be quite mobile.”
Krupke said the corn pollen that bees were bringing back to hives later in the year tested positive for neonicotinoids at levels roughly below 100 parts per billion.
“That's enough to kill bees if sufficient amounts are consumed, but it is not acutely toxic,” he says.
Hunt, who is continuing the research into the sub-lethal effects of neonicotinoids, says that for bees that do not die from the insecticide there could be other effects, such as loss of homing ability or less resistance to disease or mites.
“I think we need to stop and try to understand the risks associated with these insecticides,” he says.
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