An American entomologist is questioning the effectiveness of planting seed coated with neonicotinoids.
The controversial class of pesticides is in the news right now because of a possible link to bee deaths.
Christian Krupke, an associate professor with Perdue University, isn’t calling for a ban, as are other entomologists, but he does say North American growers should consider the true agronomic value of these treatments because the costs may outweigh the benefits.
An estimated 92 to 95 percent of corn acres in Canada and the United States are planted with seed coated with neonicotinoids. Krupke said this level of use is unnecessary because field trials at Purdue suggest the chemicals do not always provide a yield benefit.
In 2011 and 2012, Krupke and his colleagues planted corn seed with no treatment, corn with a full rate of Poncho, a Bayer seed treatment, and a third with a lower rate of Poncho.
Last year they replicated the trial four times on three fields in Indiana.
Krupke, who has evaluated yields, stand count and root damage from the two year’s of data, said the findings are clear.
“Across the board we found no differences. No statistical difference in any parameter at any location,” Krupke said.
“The data looked liked a normal distribution, if there was nothing (no insecticide) on there.”
Krupke will repeat the study this summer to account for yearly variation in insect pressure. Regardless, he questions why growers are using a seed treatment every year.
“If there is variation (in insects) from year to year, then why are we putting it on every seed, every year?” he said. “We’re putting it on (nearly) every single kernel, every year, across the U.S. and Canada…. There is a place for these compounds, but the volume we’re using is completely unsupported by this (data) or any other data I’ve ever seen…. I don’t want to say, let’s ban this tomorrow, but I do want to say the way we’re doing it is not the best way. It’s not supported by logic or science or pest populations.”
Krupke, who plans to publish a paper on his research after another year of trials, shared his findings this winter with U.S. Midwest corn growers, who were often surprised by the data.
“I don’t think (farmers) have questioned if there is a benefit. They assume that you are putting insecticide on seed, of course that’s going to be beneficial and enhance yield.”
The lack of a yield boost is particularly concerning because of the link between corn seed treatments and bee deaths.
Scientists have determined that insecticide-laden dust from corn planters has killed thousands of bees in Ontario, Indiana, Minnesota, Illinois and several other states. As well, a number of scientific papers have shown that neonicotinoids hamper bees’ ability to forage and reproduce.
In his upcoming paper, Krupke will address whether the purported benefits of seed treatments are worth the environmental risks.
Bayer wasn’t willing to comment on Krupke’s research because the company hasn’t seen the data. A Bayer Canada spokesperson said third party trials, conducted primarily in Central Canada from 2002-07, showed corn yield increases of five to 11 bu. per acre, depending on the rate of seed treatment.
The spokesperson also pointed to a CropLife America study, which found that neonicotinoid treated corn seed increased yield by 18 percent in fields with high wireworm populations.
John Cowan, vice-president of Grain Farmers of Ontario, said the latest data in Ontario shows that corn seed treatments offer a three bushel per acre yield boost.
“And as much as 20 bu. per acre where wireworm and seed maggot are found in high populations in the soil,” he said.
“What we would like to do is come up with a way to predict wireworm, seed maggot and white grub populations in individual fields, so that we might better incorporate an integrated pest management program.”
GFO has sponsored a $310,000 research project to determine the needs for seed treatment and better manage the needs of corn growers and beekeepers.
“We also want to work with equipment manufacturers to learn of potential better ways to ensure the seed treatment stays adhered to the seed and therefore gets planted and stays below ground,” Cowan said.
Krupke said such technology would be helpful, but growers should use insecticidal seed treatments only when necessary.
It does require effort to monitor pest populations in the soil, but it is possible to manage insects without a seed treatment every year, he added.
“It’s not that hard. It’s been done before. It’s just been abandoned because commodity prices have gotten so high and convenience is such a substantial thing.”
He said it’s difficult for corn growers to buy high yielding hybrids without a seed treatment. Growers should have more options when they buy corn seed, he added.
“Do you want fungicide (seed treatment) alone? Do you want fungicide and insecticide?” he said.
“At a bare minimum, there should be the choice in the hybrids they want, that they can get them with different options.”