article from the Detroit Free Press lays out the story pretty well.
In response to the reports, last Thursday DuPont sent a letter to its turf management product distributors and announced a voluntary suspension of sale and product recall for Imprelis.
According to the letter, the damage appears to primarily affect certain sensitive tree species, "such as Norway spruce and white pine, but DuPont has also received reports of damage to other species. The majority of the reported damage is concentrated in a geographic band that includes Minnesota, Michigan, Indiana, Ohio, Pennsylvania, New Jersey and Wisconsin."
According to Dallas Urban Forester, Micah Pace, no reports of tree damage have been reported here in Texas, but certainly this is an issue PMPs engaged in weed control should be aware of. Any questions about the suitability of Imprelis for use in southern lawns should be directed to the DuPont hotline at 866-796-4783.
So what does this northern herbicide story have to do with Insects in the City? The Imprelis crisis illustrates one of the inherent limitations of the pesticide registration process. Our country has an excellent system for testing and regulating pesticides, but it's not perfect. Imprelis had been tested on a variety of tree species and under a variety of conditions, but not on all species under all conditions. The fact is that safety testing for all products continues even after a pesticide has been registered and sold. The process is sometimes referred to as product stewardship, and it provides an extra measure of protection for consumers.
Obviously it would have been better and less costly for DuPont had the alleged tree sensitivity been detected during the testing phase, prior to its sale and use around the country. But to some extent real world testing is always going to be more comprehensive and rigorous than the pre-registration screening process. It shouldn't come as a complete shock that problems would arise with a new (or even older) commercial pesticide.
Rank and file PMPs should recognize this and be ready to report any unusual problems with an insecticide to the manufacturer. These reports, in turn, are supposed to be reported to EPA as part of the product stewardship process. This is the way that our regulatory system, as imperfect as it is, must work.
UPDATE (August 12, 2011). There are two recent EPA updates on Imprelis:
http://www.epa.gov/compliance/resources/cases/civil/fifra/dupontimprelis.html Describes stop sale EPA issued August 11, and notes that 7,000 incident reports have been filed with EPA since June by the Manufacturer.
http://www.epa.gov/pesticides/regulating/imprelis.html Additional notes on the issue as well as some discussion about the label limitations on Imprelis regarding use of treated clippings in compost.