Eastern White Pine Suffering Needle Loss, Weakening Trees Statewide in Maine

72e91a36b8a550d8ae4f3f27548fd5b5June 14, 2011, Maine Forest Service, Augusta, Maine — Maine residents are reporting that they are seeing more and more damage throughout the state to Eastern white pine trees, particularly with the yellowing, browning and loss of needles, according to Maine Forest Service officials, under the Maine Department of Conservation.

Homeowners, landowners, and foresters should expect to see unusual and excessive shedding of infected, 1-year-old tree needles over the next few weeks as needle diseases, caused specifically by three fungi, have reached epidemic proportions around the state, according to MFS Health and Monitoring staff.

While the needle loss has not yet caused any widespread mortality, it is a stressor and does weaken the pine, making them more vulnerable to other conditions, such as drought or insects, MFS officials said in a news release. Unfortunately, not much can be done to halt the needle loss, though good forest management can protect the trees, they said.

“It’s definitely a stressor – it’s certainly going to weaken the trees,” William Ostrofsky, MFS forest pathologist, said. “Some will get it lightly and not be affected too much, but trees that are affected can lose about 50 percent of their needles reducing their energy sources by half. They can be severely damaged by this.”

White pine normally holds two year’s growth of needles, Ostrofsky said. For the past few years, damage to Eastern white pine foliage has been observed throughout the state. Last year, the needle diseases became epidemic following high infection levels caused by the excessively wet summer of 2009. Although last year was somewhat drier, infection levels continued to remain unexpectedly high, resulting now in the premature shedding of the 1-year-old needles, the forest pathologist said.

Several fungi appear to be the cause of the needle damage, with three fungi of particular importance, Ostrofsky said. Brown spot needle blight, or Mycosphaerella dearnessii, and white pine needlecast, or Canavirgella banfieldii, were known from previous years, and this spring, another needle pathogen, Bifusella linearis, was identified in tree stands found damaged last year, he said. All three can occur on the needles of the same tree, and each one causes similar symptoms, he said.

The trees most affected are mature and over-mature trees on poor growing sites with shallow soils, and those growing at the edge of water bodies, in wet areas, and on dry, steep slopes.

In coming weeks, Maine residents may notice more needle loss, with the lower two-thirds of tree crowns affected, the forest pathologist said. After the needles drop by mid-July, the crowns of many trees will appear thin, and tree vigor will be reduced, he said

“The newly emerging, current-season needles will appear undamaged, however, and will allow trees to survive,” Ostrofsky said.

The damage is “very widespread” and affecting a large portion of the state, the forest pathologist said, adding that this week he observed damaged pines in the Leeds/Turner area. Last year, infected trees in and around western, central, and southern Maine were losing their lower, weaker branches to the disease. The needle damage has been reported from as far north as Township 7 Range 12, he said.

Ostrofsky said that the Maine Forest Service and other New England states in cooperation with the USDA Forest Service are conducting a regional survey to more accurately delineate the range of the fungi across northern New England. The survey will continue this summer and is expected to be completed early next year, he said. Ostrofsky added that changing tree stand conditions will require regular monitoring for the next few years to better assess management risks to the affected pines.

No fungicides are being recommended to control the spread of the diseases, Ostrofsky said.

“There are not a lot of things anyone can do, but one thing that can be done is not disturb the trees by doing any thinning,” he said. Other forest management practices that might disturb affected tree stands also should be avoided, he said.

“If the situation continues unabated, landowners will have to weigh the value of the pine trees at risk against the potential impact of harvest disturbance,” Maine State Entomologist Dave Struble of the MFS said.

He also said that he and his counterparts in the other northern New England states were pursuing further cooperative efforts to quantify the impact of the disease complex with an eye toward developing better management recommendations.

Eastern white pine is a significant tree in Maine, with 477 million white pine trees, 1-inch in diameter or larger, according to the most recent survey done in 2009, Ken Laustsen, MFS biometrician said. White pine makes up 2 percent of all Maine trees and 4 percent of all commercial softwood, he said. In 2009, the stumpage value of the species amounted to $32 million worth of white pine pulpwood and saw timber.