Neonicotinoid pesticides are used as a seed treatment on 80 percent of corn land and 40 percent of soybean acreage in the United States, says Purdue U in releasing a publication that assesses the pesticides value in soybeans.
As a seed coating, “neonics” provide a maximum of three weeks of protection against insect pests after planting “and are ineffective against later-emerging threats such as soybean aphids.” Purdue says published research shows that neonics are effective against sporadic early-season pests, such as wireworms or white grubs, but they lose potency before the midsummer appearance of soybean aphids, “the most potentially destructive soybean pest” in the Midwest. Planter dust contains high concentrations of neonics and can drift from fields to flowers and other vegetation, with the risk of harm to pollinators such as honeybees.
“Most soybean pests, including soybean aphid, can be managed using an integrated pest management approach, which includes a combination of scouting and insecticide use when needed,” said Purdue. “The authors recommend that farmers consult with their local university Extension services for recommendations on specific pest management strategies in their state.”
In a preliminary risk assessment, the EPA said imidacloprid, a widely used neonic, is a potential threat to honeybee hives as well as individual bees when used on crops that attract pollinators. Residues that exceed 25 parts per billion trigger effects that include death of bees and lower honey production.