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State Officials Track New Tree Infestation in Saco

July 23, 2008 - State officials are trying to determine the severity of a surprising infestation of an invasive pest -- the hemlock woolly adelgid -- discovered several weeks ago by a ranger at Ferry Beach State Park in Saco.

This is the farthest north that the pest has been found, and its spread increases concern that Maine's hemlocks -- valued for wildlife habitat, landscaping trees and lumber -- could face deadly infestations like those in southern New England and down the East Coast.

"It is a jump of several towns from where it was before," said state entomologist Allison Kanoti, who has been coordinating state efforts on the most recent infestation. "It's not something we're going to be able to eradicate. At this point we're just trying to contain it."

The barely visible brown/black bug exudes a woolly substance -- as if it were sweating it out -- that in dense clusters can make a hemlock tree look like it has been dusted by snow at Christmas. The eggs and juvenile "crawler" stage bugs can be transported easily by migrating birds, squirrels, stormy weather and humans brushing up against the trees. The bug kills the tree by sucking its sap.

"The tree weakens and can't put out buds," Kanoti said. "It's a real gradual death."

The pest is native to Japan and has been expanding its range through the eastern United States for more than 50 years. It does not kill hemlock trees in Asia or the western United States because the trees there are resistant. But they have been highly destructive on the East Coast.

The insects have been known to kill 75 percent of the hemlocks in parts of New Jersey and Connecticut. And the infestation has intensified after a couple of mild winters, said Melody Keena of the U.S. Forest Service in Hamden, Conn.

"It's having a serious impact," she said.

Maine has fared better because of colder winters here. Temperatures of around 20 degrees below zero will knock back, but not entirely destroy, a population, Kanoti said.

The hemlock woolly adelgid was first discovered in Kittery in 2003, and there is a gradually expanding quarantine on hemlock products in several York County towns. The pest has already killed some hemlock trees in southern Maine, Kanoti said.

A two-week search of the 130-acre Ferry Beach State Park has turned up only light infestations in about 50 trees.

"It's somewhat spotty in those sites and the infestations are fairly light, but it has spread out into the forest," Kanoti said. The park's forest is contiguous to a hemlock forest that is on neighboring private property, she said.

On Thursday, Kanoti and other inspectors were visiting that property and other nearby spots to see if there are other infested trees. One nearby area, across a road from the park, is a section of the Rachel Carson National Wildlife Refuge.

Kanoti said they are particularly concerned about infestations in high-traffic areas because people brushing up against the trees can unwittingly transport the eggs or "crawler" stage bugs to new areas. The woolly adelgid, with a roughly six-month life cycle, can live for about three weeks without feeding, she said.

Fighting the woolly adelgid is a "high priority" for the Forest Service because hemlock plays a unique role in Maine's ecosystem.

Hemlocks provide dense coverage and winter nourishment for the state's deer herd, and there are several migratory birds that only nest in hemlocks, Kanoti said. Located near streams, hemlocks moderate the temperature of the water, which is in turn important for insects and -- further up the food chain -- the fish that feed on those insects.

"There is no tree species that does a good job of replacing hemlocks," Kanoti said. "There's nothing else quite like it."

The pest also has had a big impact on commercial nurseries. Hemlocks are no longer popular landscaping trees in southern New England, and demand for them has slowed somewhat in Maine because of concerns that they could be affected.

"It used to be when you wanted to plant a screen and you wanted evergreen, the first thing you thought of was hemlock," said Jeff O'Donal, owner of O'Donal's Nursery in Gorham.

He still sells hundreds of the trees a year, but now has to ship some of them in from Ohio, a state outside the quarantined areas.

O'Donal said he's optimistic that Maine's cooler climate means the hemlocks here will be stronger and more resistant to devastating infestations.

"Our trees are reacting to this insect far better and far different than the ones in southern New England," he said. "It's moving very slowly compared to Connecticut and doing far less damage."

But, he said, the spread to Saco is troubling. "That's too close," he said. "Ferry Beach is way too close to Pine Point and Scarborough. Eventually it will cross the border and all bets are off."

Park ranger Janet Mangion, who had been trained in 2005 on how to spot the pest, first noticed the bugs at Ferry Beach State Park in late June. By early July, state entomologists had confirmed that the small flecks were the woolly adelgid.

Since then, Forest Service field technician Wayne Searles has been walking the roadways, paths and animal trails through the 130-acre park.

"I zig and I zag," he said, starting off with the most heavily traveled paths, and by this week, breaking new paths in more heavily forested areas. So far, he has discovered primarily small clusters of light infestations. "I'm trying to get a feel for the whole park," he said.

Kanoti said people in the area should monitor hemlocks for infestations and report them to the Forest Service lab at 287-2431. "We haven't found it in a new town in a couple of years, but maybe people in the Saco area aren't necessarily used to looking for it," she said. "We want people to take time and look at their hemlocks."

A hemlock tree can look healthy for up to 10 or 15 years before the infestation kills it. In the meantime, there are few effective treatments.

Chemical sprays and injectable chemicals can be used on individual trees, but the woolly adelgid has no natural predators. The state did "a lot" of chemical treatments in 2001, when infested nursery stock hit the state, Kanoti said, and it seemed to be effective.

The Forest Service also introduced several predator beetle species in 2007, but it is too early to know if they will be effective over the long haul. There are also efforts under way at the University of Vermont to develop a fungal pathogen, she said.

Kanoti said she hoped they would have a plan for how to treat the infected trees at Ferry Beach in about a month.


By NOEL K. GALLAGHER, Staff Writer, July 18, 2008, Portland Press Herald


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