New study in progress | Researchers examining whether seed coatings boost yields, kill bees
Purdue University entomologist Christian Krupke is seeking an answer to a question that he believes scientists have ignored for too long: do seed treatments really protect corn crops from insects?
Last year, Krupke and his colleagues conducted a pilot study in which they grew corn coated with an insecticide next to corn without a seed treatment.
The experiment was done at only one site, but the results showed the seed treatment didn’t boost yield or provide additional insect protection.
“It didn’t show a benefit,” said Krupke, who was raised in southern Ontario and took his undergraduate training at the University of Guelph.
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“Anytime you have one site, one year, you have to take it with a huge grain of salt … so this year we have three sites and it’s a larger, more rigorous study.”
The results won’t be finalized until later this year or early in 2013, but corn growers and beekeepers in Ontario may be interested in the outcome because seed treatments became a hot issue this spring in the province.
Hundreds of thousands of honeybees died in Ontario during the corn planting season in May, with some beekeepers losing 40 to 50 percent of their bees.
There were probably 100 reports of piles of dead bees near hives this spring, said John Van Alten, president of the Ontario Beekeepers’ Association.
Health Canada and the Ontario agriculture and environment ministries initiated an investigation into the bee deaths, and early results suggest that neonicotinoid seed treatments killed the bees.
“The preliminary results on the samples that were sent in, I believe about 70 percent … that were tested for clothianidin, came back positive,” said Van Alten, who runs 1,500 hives and sells honey under a brand called Dutchman’s Gold near Hamilton, Ont.
Krupke decided to examine the efficacy of seed treatments as part of an investigation into bee deaths at corn seeding time in Indiana. For several years, beekeepers in the state have found thousands of dead bees outside hives during planting season.
In January, Krupke and Greg Hunt, a genetics professor and honeybee specialist at Purdue, published a paper in the journal PloS One that demonstrated a link between corn seeding and bee deaths. Their research showed that high concentrations of two insecticides, clothianidin, a Bayer Crop Science product, and thiamethoxam, a Syngenta insecticide, were present in the dust and exhaust of seeding equipment.
“We know that these insecticides are highly toxic to bees; we found them in each sample of dead and dying bees,” Krupke said, noting the coating rubs off when corn seeds bounce and grind against each other during seeding.
“Whatever was on the seed was being exhausted into the environment. 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.”
In June, Health Canada’s Pest Management Regulatory Agency announced it would re-evaluate the environmental risks of clothianidin, thiamethoxam and imidacloprid, another Bayer neonicotinoid. The products are sold under the names Poncho, Cruiser and Gaucho, respectively.
In particular, the PMRA wants to determine if these products, including seed treatments, are harmful to pollinators such as honeybees.
The PMRA isn’t expected to publish the results of its assessment for several months, but corn growers in Ontario are paying close attention.
In a news release in early September, Grain Farmers of Ontario said it’s too early to judge seed treatments, even though there might be a connection between the products and bee deaths.
“Farmers must take everything into consideration before making any decisions in the situation going forward and we look forward to updates as they become available,” said director Kevin Armstrong.
Krupke said it’s strange that growers are attached to these products because there is little evidence that insecticidal seed treatments protect corn and crop yields.
“The argument is often put forward that farmers need these (tools) to grow corn. Well, that’s never been shown to be true,” he said. “There’s not good efficacy data to say that this is warranted at all.”
Krupke pointed the finger at himself and other scientists.
“It’s disgraceful that we have so little (data). We, as public sector researchers, have dropped the ball on this,” he said.
“It’s not industry’s job to point out all the caveats associated with their products. They’re selling products.”
Krupke hopes to fill the void with his trials on corn seed treatments at Purdue. Despite his misgivings, he noted that insecticidal seed treatments can be useful.
There are regions in North America and times where the treatments can be useful to protect corn from insects. However, he also said it’s absurd to apply insecticidal seed treatments everywhere and every time.
“I would say there’s a role for insecticidal seed treatments. But to say that every single kernel requires them is not at all supported by any data.”
Van Alten doesn’t want this to turn into a battle between honey producers and corn growers. Instead, he wants to work with producers, government agencies and industry on solutions.
“The biggest thing is we would like to see something developed that would keep that seed treatment … on the seed … so that it actually stays on the seed where it belongs,” he said.
His association doesn’t have a position on the use of neonicotinoids, he added.
However, he said the class of pesticides does harm bees.
“We know that if they end up in the beehive, or where the bee is foraging, it has disastrous results…. We definitely don’t want to see anything of this magnitude again. It’s hard to keep a beekeeping operation going when your bees are being poisoned.”
