A two-year, multi-state study, paid for by soybean checkoff funds, found no yield benefit from planting soybean seeds coated with a neonicotinoid insecticide compared to untreated seeds. The study was a joint effort of seven universities in the Plains and Midwest and concluded that, as far as expenses and pest control were concerned, farmers were better off to scout their fields and apply insecticides as needed.
“Farmers wouldn’t get an advantage from putting insecticide on soybean seeds,” said Bruce Potter, a University of Minnesota pest management specialist. The study looked at the effectiveness of insecticide treatments against the soybean aphid, a key pest, said Purdue, one of the universities that took part in the research. Neonicotinoid-coated seeds are widely used.
Purdue entomology professor Christian Krupke said the seed coatings are effective for a maximum of two weeks. The benefit of the insecticide has worn off by the time that soybean aphids typically reach damaging population levels in late July or August. A study of neonicotinoid coatings of corn seed, conducted by a doctoral student under Krupke, was published early this year and reported a similar conclusion.
Separately, DTN reported that “more than 94 percent of honey bees in the state of Indiana are at risk of exposure to varying levels of neonicotinoid insecticides, including lethal levels, during corn planting,” according to Purdue research. “That exposure occurs when the insecticides, which are coated on individual seeds, ‘dust off,’ from those seeds during planting and the dust drifts beyond the field borders. The study also concluded that the neonicotinoid treatments in Purdue corn research plots from 2012-2014 did not provide any yield benefit.”