Research review | Report finds minimal yield boost from seed treatments
An American environmental group says neonicotinoid seed treatments offer minimal yield benefits and cause “widespread environmental and economic damage.”
In a report released in late March, the U.S. Center for Food Safety said it reviewed 19 published studies on the potential yield boost from neonicotinoid seed treatments, which are applied to nearly every corn, canola and soybean seed in North America.
Eight studies found neonics didn’t provide a significant yield benefit, while 11 studies showed inconsistent yield gains, the report authors said.
“What we learned in our thorough analysis of the peer-reviewed science is that (the) claimed crop yield benefit is largely illusory, making their costs all the more tragic,” said Peter Jenkins, report co-author and Center for Food Safety attorney.
Purdue University entomologist Christian Krupke and U.S. Department of Agriculture entomologist Jonathan Lundgren acted as reviewers for the study.
Krupke has conducted several field studies looking at the yields of corn treated with neonicotinoids versus corn that received no treatment.
Krupke said the findings are clear after evaluating yields, stand count and root damage from two years of field trials in Indiana.
“Across the board we found no differences. No statistical difference in any parameter at any location,” he said last year.
“The data looked liked a normal distribution, if there was nothing (no insecticide) on there.”
Lundgren said farmers should question why they are planting neonic-coated seed every year.
“Public sector research on insecticidal seed treatments in soybeans … consistently shows that spraying pests when they exceed thresholds is more profitable than prophylactic use of insecticidal seed treatments.”
Most of the studies cited in the report were American studies on corn or soybeans. There was only one Canadian study on canola.
Bob Elliott, an Agriculture Canada integrated pest management specialist in Saskatoon, wasn’t willing to comment because he hadn’t evaluated the studies mentioned in the Centre for Food Safety report.
Nonetheless, he said Canadian seed treatment research indicates the products protect canola from flea beetles.
“Over 34 test-years, neonicotinoid seed treatments reduced flea beetle damage after 21 days by eight to 11 percent (29 of 34 years), improved seedling emergence after 21 days by nine to 13 percent (31 of 34 years), improved stand establishment after 28 days by nine to 12 percent (30 of 34 years, … and seed yield by six to 13 percent,” he said.
“Clearly, results from corn and soybean are at odds with what we have found in canola.”
The Center for Food Safety report didn’t refer to Elliott’s work, but it did mention a study by Julie Soroka of Agriculture Canada.
In the 2000s, Soroka evaluated the Bayer insecticides clothianidin and acetamiprid and their efficacy on flea beetles.
Soroka wanted to know if canola growers could reduce the percentage of treated seed and maintain yields.
Reducing the amount of treated seeds by 33 percent didn’t compromise seedling growth, plant density, yield or cash return, although treating 100 percent of the canola seeds in years with high levels of beetle feeding consistently boosted yields.
However, 100 percent treatment didn’t provide the same benefit in seasons with low to moderate flea beetle pressure.
Soroka said conditions have changed on the Prairies since the study. Striped flea beetles, which are resistant to neonics, have increased, and farmers are growing different varieties of canola.
The Centre for Food Safety report said the widespread use of neonicotinoids has made integrated pest management obsolete. It said farmers should apply pesticides only “if economic damage thresholds are exceeded,” but neonic seed treatments are used even if insects are not a threat.
The Centre for Food Safety said the prophylactic application of insecticides should be terminated. It is not cost effective for farmers and undermines integrated pest management principles.
The study included comments from Tracey Baute, an entomologist with Ontario’s agriculture ministry.
“Based on my experience, only 10 to 20 percent of the corn and soybean acres are actually at risk (for) most of the soil pests on the (neonicotinoid) product labels.”
The Center for Food Safety wants the U.S. Environmental Protection Agency to suspend the registrations of all neonicotinoid seed treatments until the true costs and benefits are fully understood.