A study published last week in the Proceedings of the National Academy of Sciences - a peer-reviewed journal - researchers from the Cary Institute of Ecosystem Studies report they have found Bt from nearby corn fields in neighboring streams.
Six months after harvest, the researchers surveyed 217 stream sites in Indiana and found dissolved Cry1Ab proteins from biotech corn present in stream water in about one-quarter of the sites. They did find that 86% of sampled sites had corn residues in the streams and ad 13% of the sites corn byproducts contained detectable levels of Bt.
Reaching beyond their initial study, the researchers determined that in 100% of the sites containing Cry1Ab-positive corn waste in the active stream channel were within about 1,500 feet of a field where corn had been planted the previous year. They extrapolated their data to find that 91% of the 160,000-plus miles of streams and rivers in Iowa, Illinois and Indiana are located within 1,500 feet of a corn field.
The study raises questions about what happens to Bt after the crop is harvested. Finding the biotech component prevalent six months after harvest tells the scientists the product is "persistent in the headwater streams of a Corn Belt landscape," according to the paper. The fact that only one-quarter of the streams surveyed showed Bt in the water may bear further review.
For farmers this news has gotten wide coverage on the paper itself, but in a quick Google search this morning little reaction/response from industry. The paper raises questions about the potential for Bt to reach non-target organisms. Bt is a naturally occurring soil bacterium toxic to lepidopteron insects - including costly European corn borer. This is a costly pest that was difficult to control before the advent of the technology. Since the technology was brought to market in 1996, the amount of Bt corn planted has risen to 63% of the U.S. crop, according to USDA data.
More work is needed to determine how persistent the biotech product is in corn waste and what that might mean for the future. Raising questions is what good science does; and that investigatory process continues as more scientists review the research and do more work of their own.