A new chemical treatment to keep lawns green and weed-free is having an unanticipated side effect on some evergreen trees.

It's turning them brown.

"We have seen varying degrees of damage to woody plants," Don Long, general manager of local lawn-care company Tomlinson Bomberger, said Tuesday.

"The general consensus seems to be patience," he said. "Wait and see. A plant's recuperative abilities are stronger than many people think.

"Certainly there is going to be some plant loss. Certainly there are going to be some that recover."

Tim Abbey, of the Penn State Cooperative Extension in York, said the issue has cropped up in several regions, with some of the biggest problems seen in the stretch between Lancaster and Philadelphia.

"It's shown up in other states," he said. "The Northeast has experienced some fairly widespread damage."

Norway spruce and white pine trees have been hardest hit, although Douglas fir, other kinds of spruce and some yews have been affected as well.

Some trees have died, Abbey said, while others have lost a year's growth but seem to be recovering.

Long said the culprit is a new lawn-care product that Tomlinson Bomberger and "many other" lawn-care providers began using — "in some cases last fall, in our case this season."

"It's proven very effective in weed control on lawns," Long said. However, he added, "it's gone beyond its intended purpose."

The product suspected of causing the damage is called Imprelis, a new product manufactured by DuPont.

"The product has been used nationwide," Long said. "The damage seems to appear in pockets. It's not happening everywhere."

There is speculation, he said, that the severity of the problem could be related to weather conditions — such as rainfall.

"It could be the way the stars and the moon lined up," Long said. "But this is obviously … something that wasn't tested for."

According to information posted on DuPont's website, the herbicide "contains a single active ingredient and exhibits favorable environmental and toxicological characteristics."

The active ingredient, aminocyclopyrachlor, "is the first compound in an advanced generation of carboxylic acid herbicides," promotional materials for the product state.

"Discovered by DuPont, this new generation of chemistry has unique properties at both the molecular and whole plant levels that translate into more powerful herbicidal activity."

However, DuPont then warns, the company is "investigating reports of various symptoms on certain species of trees and whether applications of DuPont Imprelis herbicide may have contributed to observed symptoms."

The company urges lawn-care professionals to avoid using the product in proximity to white pine or Norway spruce trees in particular.

Abbey said the product label recommends applying the herbicide "a safe distance from woody plant material."

"I don't know what happened this year — if it's related to the excessive amount of rainfall this spring," he said.

"DuPont is working on it," he added. "It's too early to tell what the long-term ramifications will be."

However, Abbey cautioned tree owners from assuming any and all tree damage stems from Imprelis.

"Any individual homeowner would know if someone treated their lawn. They should find out if someone applied that material. If it wasn't applied, then it's some other biological or environmental problem," he said.

Some trees are suffering from other woes this year, he said, ranging from fungal infestations to long-term damage sustained during last year's drought or the cold, dry winter that followed.

If Imprelis is the cause of tree damage, Abbey said, homeowners should work with the company that applied the herbicide.

"And that company needs to be in touch with a DuPont representative … for remediation of the problem, whether the plant needs to be replaced or not," he said.

The U.S. Environmental Protection Agency approved the use of Imprelis last year for commercial use in controlling dandelions, ground ivy, violets, clover and other weeds in lawns.

The soluble liquid formula is absorbed through foliage and roots of target weeds, according to Penn State research. Because it is absorbed very slowly into the soil, rain — even days or weeks after the product's application — can flush the herbicide into groundwater sources or carry it to the roots of nearby trees.

It's not available for sale to homeowners.

DuPont has been targeted in two federal class-action suits — filed on behalf of a Johnstown woman and several Indianapolis golf courses — asking that the product's use be discontinued and tree owners be reimbursed for their losses.

"The evidence is quickly piling up that Imprelis is attacking trees as if they are weeds," Jonathan Selbin, a lawyer in the suit, said Monday.

tknapp@lnpnews.com