Neonicotinoid pesticides, getting an increasingly closer look for a possible tie to pollinator health issues, can be found in streams throughout the Midwest, a seven-state, nine-stream U.S. Geological Survey study has found.
The study is the first broad-scale look at neonics – an effective broad-range insecticide – in the Midwest, USGS says.
In all, nine rivers and streams, including the Mississippi and Missouri Rivers, were included in the study. The rivers studied drain most of Iowa, and parts of Minnesota, Montana, Nebraska, North Dakota, South Dakota, and Wisconsin.
USGS says these states have the highest use of neonicotinoid insecticides in the U.S., and the chemicals were found in all nine rivers and streams. In Iowa alone, USGS points out, the neonicotinoid clothianidin's use on corn has almost doubled between 2011 and 2013.
Of the three most often found chemicals, clothianidin was the most commonly detected, showing up in 75% of the sites and at the highest concentration. Thiamethoxam was found at 47% of the sites, and imidacloprid was found at 23%. Two, acetamiprid and dinotefuran, were only found once, and the sixth, thiacloprid, was never detected.
Locations of sites in Iowa sampled for neonicotinoids in 2013. Mississippi River and Missouri River site watersheds are shown in the inset. (USGS graphic)
Neonics are typically applied as a seed coating before planting, which correlates to USGS' findings, says scientist Michelle Hladik, the report’s lead author.
“We noticed higher levels of these insecticides after rain storms during crop planting, which is similar to the spring flushing of herbicides that has been documented in Midwestern U.S. rivers and streams," Hladik said.
She noted that the study indicates neonics – which dissolve easily in water but do not break down quickly in the environment – were detected prior to their first use during the growing season, which indicates that they can persist from applications in prior years.
The U.S. Environmental Protection Agency has classified all detected neonicotinoids as not likely to be carcinogenic to humans, but recent concerns have flared that they could impact the health of pollinators.
While the EPA and the USDA last year said in a review that several factors may be to blame for recent honey bee colony losses, pesticide exposure should be under continued review.
Last year, the European Commission elected to temporarily ban lothianidin, thiametoxam and imidacloprid pesticides on concerns that they impact bee health.