ACADIA NATIONAL PARK — The death of more than 100 trees along Sargeant Drive this summer was the result of the first confirmed infestation of red pine scale in Maine, according to Allison Kanoti, a Maine Forest Service entomologist.
Red pine scale is a small insect that is native to Japan. In this country, it was first detected in Connecticut in 1946. But scientists believe it originally came to the United States on trees planted at the 1939 New York World’s Fair.
“In most places where the insects are established, the trees die fairly quickly after becoming infested,” Kanoti said.
Not much can be done to keep an infestation from spreading, in part because red pine scale is carried by birds and the wind. And because the insect is originally “from away,” Kanoti said, it has no natural enemies here.
“There were some attempts at introducing biological controls, that is, predators, in Connecticut, but those weren’t very successful,” Kanoti said. “There has been some recent work in China looking at diseases [that might be used to combat red pine scale], but that’s not in our toolbox right now.”
Fortunately, red pine scale doesn’t affect other species of trees. And red pines, while abundant in many parts of the state, are far from the most prevalent species of conifers in Maine. Eastern white pine, northern white cedar, balsam fir, hemlock and red spruce are more common. And in most places, red pines are interspersed with some of those other species, so their deaths don’t usually leave large swaths of bare trees. That was the case on the west side of Norumbega Mountain above Sargeant Drive, Kanoti said.
Although that infestation was the first in Maine to be confirmed by laboratory analysis and field visits, it almost certainly was not the first in the state or even on Mount Desert Island. A “pest alert” issued by the Maine Forest Service on Monday said, “It appears the insect is well established in the area around Northeast Harbor…and it has contributed to significant red pine mortality there.”
In addition to the scale, red pines in many parts of Maine, including Mount Desert Island, have been assaulted by two “shoot blights,” primarily one called Sirococcus conigenus.
“That has been very damaging, contributing to the mortality of red pine in the [Mount Desert Island] area,” Kanoti said.