By Joseph N. DiStefano

Imprelis looks like the kind of green-ish, high-end, proprietary product DuPont chief executive Ellen Kullman needs to build her arsenal of biotech and agricultural chemicals as it rebuilds worldwide sales from its Wilmington headquarters.

Less than five ounces an acre, the company told suppliers, kills clover, dandelions, plantains, wild violets and the tough ground plant golf course managers call "creeping Charlie."

The high concentration makes it cheaper to ship, which saves fuel. DuPont said hundreds of tests showed Imprelis spared grass, trees, landscape shrubs, and crawling and walking creatures, if used right.

Dealers listed Imprelis for hundreds of dollars a gallon, and it flew off shelves.

Then the evergreens started turning brown.

By June, state agricultural extension services in Pennsylvania, Michigan, and Indiana were naming Imprelis as a suspect in the blighting of Norway spruce and eastern white pines, Northern trees which are not native to much of the country but have been planted by the millions in yards, golf courses, cemeteries and parks, in the path of the turf chemical industry's marketers.

After spraying Imprelis in April and May, "professional turf-grass managers from Iowa to New Jersey experienced damage to certain tree species, primarily Norway spruce and white pine," Pete Landschoot, professor of turf-grass science at Pennsylvania State University, wrote in a June warning posted by the university's extension service.

"In some cases, injury does not progress much further than slight curling and browning of new growth; however, in other cases complete dieback is observed. In severe cases, the entire tree turns brown and begins to lose its needles."

It's as if the trees were being poisoned through the roots, from herbicide spread deep by the soaking spring rains, he added. Landschoot noted DuPont's labels warned users to be careful where they spray, since Imprelis has "high potential for reaching surface water via runoff for several months after application."

DuPont on June 17 sent a warning letter to dealers and sprayers. "Do not employ Imprelis where Norway spruce or white pine are present on, or in close proximity to, the property to be treated," warned Michael McDermott, head of suburban Wilmington-based DuPont Agricultural Products, who had introduced Imprelis at industry gatherings all winter.

Not that DuPont was taking the blame: "In most cases" of damaged trees, he wrote, Imprelis had been mixed with other weed-killers or liquid fertilizer, and there "may have been errors" in how it was used.

Since then, news reports have been coming in across the country about trees in nurseries, parks and homes left brown and stark, as if they were weeds.

On Friday, a week after the Detroit Free Press wrote a story, a polo club in Michigan filed what may be the first lawsuit against DuPont over damage from Imprelis, the Bloomberg Law service reported.

DuPont will not say how much Imprelis it has sold. The company is "working to understand" what happened, but it doesn't consider the problem will materially affect financial results, spokeswoman Kate Childress said.

DuPont has a lot of experience managing useful products with damaging side effects. Looks like Kullman and McDermott are about to get some more.

Leaving clients and potential users to wonder. "I started getting e-mails warning about this back in May," from growers' groups, Vince Marrocco, chief horticulturalist at the University of Pennsylvania's Morris Arboretum in Chestnut Hill, said.

One of Imprelis' seeming virtues - that a few ounces cover an acre - turned Marrocco off: "Anytime I see a chemical, that you use that little of it, I don't use it, because it's hard to apply. Gallons an acre is more my speed. You don't have to be as exacting."

Printed in the Philadelphia Inquirer, Sun, Jul. 17, 2011
http://www.philly.com/philly/columnists/joseph-distefano/20110717_PhillyDeals__DuPont_catches_flak_over_Imprelis_weed-killer.html