DURHAM, N.H. – Forestry officials plan to take a closer look at a tree disease that is infecting white pines in New Hampshire.

Known as Caliciopsis pinea, state officials first identified the canker in New Hampshire in 1997 but said little is known about the disease. It particularly afflicts white pines in New Hampshire’s central and southern parts, and is also found in Maine, Vermont, Massachusetts, New York, Virginia, West Virginia and Georgia.

Kyle Lombard, manager of the New Hampshire Forest Health Program, said the agency wants to figure out how serious pine canker is and how much damage it does to the trees.

He said the canker starts with a lesion on the bark, penetrating and causing dead spots that affect a tree’s ability to grow. Sap also can be visible on the bark, and the tree’s crown may be thin.

Private forester Craig Birch said officials first noticed the canker about eight years ago at Beaver Brook Association, a nonprofit in Hollis, N.H., that operates a 2,000-acre nature reserve that is open to the public.

“We’ve been trying to get to the bottom of it ever since,” the Beaver Brook volunteer said.

Birch said infection seems to occur in white pines in dry, sandy soil, and infected trees seem to grow slowly.

Isabel Munck, a forest pathologist with the U.S. Forest Service, said the fungus spreads through spores.

She said scientists did some tree thinning in recent years to see if reducing the density of infected trees in an area would help nearby trees fight off the disease. Now, experts will cut and examine some trees left in those stands to measure their growth and see if there is less or more disease inside them.

“This is our first step to even see if what we’re recommending is working,” Munck said.

Lombard said that as part of the study, experts will follow infected white pine logs to saw mills to measure any loss in the lumber’s value.

“White pine is probably still the king of the forest in New Hampshire … so anything that affects growth rates and the timber industry, it’s important to get a handle on it,” he said.