Invasive insects threaten trees in Portland’s Baxter Woods

This sign greets people near the beginning of the walking trails through Baxter Woods in Portland. City officials are taking steps to fight back an early invasion of hemlock woolly adelgid at the site by releasing beetles that feed on the insects.
Seth Koenig | BDN
This sign greets people near the beginning of the walking trails through Baxter Woods in Portland. City officials are taking steps to fight back an early invasion of hemlock woolly adelgid at the site by releasing beetles that feed on the insects. Buy Photo
Posted May 22, 2014, at 12:26 p.m.
Tiny predatory lady beetles, Sasajiscymnus tsugae, are used to control populations of invasive hemlock woolly adelgids.
Courtesy of Dr. Carole Cheah, Connecticut Agricultural Experiment Station
Tiny predatory lady beetles, Sasajiscymnus tsugae, are used to control populations of invasive hemlock woolly adelgids.

PORTLAND, Maine — Invasive insects that prey on hemlock trees have been found in Portland’s Baxter Woods, and city and state officials are planning swift action in an attempt to wipe out the bugs.

“Two years ago we found them on Great Diamond Island and they devastated the hemlock on the island,” city arborist Jeff Tarling said.

Tarling said that after the invasion of nearby Great Diamond Island, his workers began looking for the telltale signs of the insects in Baxter Woods, which boasts thousands of the hemlocks and presented a natural next target for the pests, which can be transported by birds.

This January, student researchers from Catherine McAuley High School discovered the cotton-like adelgid egg sacs on the undersides of hemlocks in the forest park.

“I think we’re right on the doorstep of this invasion,” said Tarling, who on Wednesday helped students at Portland’s East End Community School plant apple trees as part of the city’s Arbor Week celebration.

“After seeing the damage on Great Diamond Island, we may not lose all of our hemlocks, but it sure feels that way,” he continued. “Hemlock is really sensitive. When it goes, it doesn’t come back.”

The invasive insects feed on hemlock sap and inject a toxin that ultimately strips the tree of needles. Tarling said the infections have yet to kill any of Baxter Woods’ hemlocks, and he hopes city and state efforts to fight back the woolly adelgids will be effective before they do.

That effort will include the local release of thousands of predator lady beetles, which eat the hemlock woolly adelgid, on May 29.

“It is not a silver bullet, but it’s the best management tool we have in the forest at this time,” said Alison Kanoti, forest entomologist with the Maine Department of Agriculture, Conservation and Forestry, in a statement. “This is a long-term solution; results will not be immediate.”

Tarling said the small, black beetles have been used effectively in the past, and don’t become an invasive problem themselves because they only eat the hemlock woolly adelgid. Once that food source has been wiped out, the beetles die off or find a new population of the invasive bugs to feed on.

Hemlock woolly adelgid is native to Japan and first arrived in North America in the 1950s, according to the department, but wasn’t seen in Maine until a discovery in Kittery in 2003.

While sightings of the invasive insect have been scattered around the state since then, it has most recently been found spreading in Hancock County, in forested areas in Bar Harbor, Ellsworth and Blue Hill.

Tarling said that Maine’s recent cold winter killed off approximately 80 percent of the hemlock woolly adelgid here, but cautioned that the remaining insects multiply rapidly, and the weather is turning favorable for them.

The state forestry department warned that “thousands of offspring, called crawlers” spend the spring and summer “crawling around, sifting down through the tree canopy and drifting on the breezes in infested hemlock forests.”

In a statement, Gov. Paul LePage urged Mainers to keep a lookout for the invasive insects.

“Public awareness of the threats posed by invasive species like the HWA is critical to minimizing their impact,” he said. “Once they have taken hold, it is very difficult and expensive to contain and/or eliminate them. That is why early detection by the public and department professionals is important.”

The city of Portland is hosting a public meeting on Wednesday from 6 to 7 p.m. to discuss the hemlock woolly adelgids as well as other matters related to Baxter Woods, including a reminder that city ordinances demand that dogs be under voice control when walking there. The meeting will take place at the Wilde Chapel at Evergreen Cemetery.

 

SEE COMMENTS →

ADVERTISEMENT | Grow your business
ADVERTISEMENT | Grow your business

Similar Articles

More in Portland