Sharon Collman’s quest for answers started at her childhood home.

There, in Shoreline, 60 years ago, her mother planted a tiny Western white pine sapling that would grow strong and sure until a few years ago, when it inexplicably began to die.

Collman, an extension educator and entomologist, knows a few things about trees. A healthy, well-cared-for tree in her mother’s front yard should live at least 200 years.

She didn’t know it then, but she had stumbled on a problem that has the potential to devastate certain species of pines across Western Washington. It’s already killing Western white pines from Mill Creek to Seattle.

Together Collman and a Snoho­mish arborist devoted hundreds of hours trying to get to the bottom of what was killing trees and how it could be stopped.

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Since the tree’s death at her mother’s house, Collman had begun to notice dying white pines everywhere. She’d drive to work and see white pines on the same march toward death.

Over time, she noticed a progression. First, the canopy would thin. Branches at the base of the tree would turn brown. White pitch would bubble out of the wood, sometimes in large enough quantities to splash onto the plants below. After a few years, the entire tree would fade to a sickly tan. Some did the opposite, dying top to bottom.

When her mother had her Western white pine taken out, the tree was dry inside. One of the branches was ringed with an odd blue stain. Collman describes herself as having a hobbyist’s grasp of tree health, but as part of her extension duties, she is well-versed in diagnosing many plant diseases. The police once questioned her for hunting weevils in the middle of the night in a highway island with a flashlight.

She couldn’t get this puzzle out of her mind.

“It was like, ‘Well, why now?’” she said.

It’s normal for white pine needles to turn brown and drop in the fall, she said.

What she was observing was something else entirely. The branches on the white pines were dying out to their tips.

She ruled out blister rust, a well-known fungus that can invade trees and form spindle-shaped bundles on branches. She knew a tree that dies from drought starts dying from the top down, as water-starved limbs suck up any available moisture first.

She knew someone who could help.

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Dan Douglas has worked as an arborist and a horticulturist in this area for more than 30 years. Intense and blunt, Douglas isn’t shy about knocking on strangers’ doors if he spots a tree in trouble.

He heard other arborists talking about white pines dying in large numbers and initially didn’t pay attention. Then, he and Collman went on a field trip to north Seattle. She showed him a Western white pine clearly dead at a Seattle golf course.

From years of diagnosing sick trees, Douglas has learned it’s nearly impossible to tell what killed a tree once it’s dead. Pathogens and insects are attracted to weakened trees, and it can be hard to distinguish the grave robbers from the killers.

The ideal specimen is a tree starting to show stress. Not far away, Douglas spotted it. The Western white pine looked ill, almost anemic, with yellowing needles and a thinning canopy.

The two nicked away a piece of the bark and underneath found some black streaks.

What he saw unsettled him. He wondered whether it had the potential to spread. And he wanted to know what it was.

“This was something we knew we hadn’t seen before,” he said.

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Douglas and Collman weren’t the only ones to notice white pines in the area dying. But the dying trees were either dismissed as victims of blister rust or the cause wasn’t explored.

White pines have been declining for years but state Department of Transportation officials began to notice an uptick in deaths, said David Peterson, the principal landscape architect for the organization.

“I have seen it accelerate over the last five years,” he said.

He assumed the problem was related to blister rust. They don’t have the resources to take a closer look at the problem. Instead, the agency focuses on monitoring failing white pines and taking them down if they pose a threat to public safety, he said.

The Western white pine has little economic value, plant diseases are complex and research money is hard to come by, especially in these hard times, Douglas said.

“People spend their money studying human diseases — and rightly so, that’s more important.”

University researchers conduct most of the work into tree diseases. Their projects are largely funded by grants from the government and private business, entities interested in economically valuable crops such as timber and Christmas trees, he said.

Since white pines are scattered among other trees, their widespread decline isn’t as apparent as it might be with trees such as Douglas firs, which grow abundantly in large swaths.

“Everybody was talking about what was wrong with the white pines, but nobody was doing anything,” he said.

He spent the next two years contacting every official and researcher he could find who might have an answer. He found Western white pines dying across the area with the same mysterious symptoms.

He arranged to watch as a white pine at Washington Park Arboretum in Seattle was pulled down. Inside the tree, he found blue stain, a fungus that invades the sapwood of trees, clogging the conductive tissues.

He began to get some answers with the help of university researchers in British Columbia. An expert there agreed to test samples of the blue stains Douglas had found in area trees.

The results stunned him. One of the trees, from a specimen in Mill Creek, had not one but several types of blue stain. At least one of the stains appears to be a type that researchers hadn’t seen in Western Washington. The tests need to be independently verified at least twice more before Douglas can say so definitively.

He’s now convinced beetles are attacking both the roots and the tops of the trees, depositing the blue stain funguses when laying eggs.

His theory is eerily similar to what’s happening in other parts of the West with different types of pines.

Bark beetles have killed millions of acres of pines from New Mexico to British Columbia. The reasons are varied: Programs designed to suppress forest fires have let pines grow big enough to be susceptible to beetles. And pines weakened by droughts, rising global temperatures, and competition from other species are mores susceptible to beetles, said Greg Filip, a regional forest pathologist based in Portland, Ore., for the U.S. Forest Service.

Filip guessed white pines may have begun declining more rapidly because they’ve become stressed by blister rust or other factors, which left the trees susceptible to the beetles.

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Douglas believes it’s unlikely this is a disease spreading simply because trees are stressed.

“White pines have died in well-maintained areas, including gardens with added water,” he said.

Instead, Douglas thinks longer summers are increasing beetles’ ability to attack white pines.

Douglas is concerned whatever is happening might jump to other types of pines. He’s noted the same symptoms in at least two other kinds of pines.

Both Douglas and Collman hope to convince more specialists to examine the problem.

“We need a plant physiologist, somebody who knows soils, a plant pathologist and a forest entomologist,” Collman said. “They need to look at the sites and figure out what are the extenuating factors going on.”

The end goal would be to develop a plan to slow the spread of the disease, Douglas said. It’s unlikely anyone can develop a cure, but it’s possible they could slow it from spreading. If it’s indeed spread by a certain type of beetles, workers could use pheromone traps to throw beetles off the scent or even inject a targeted pesticide into vulnerable trees.

Douglas worries about the widespread death of these trees and the possible ecological ramifications to animals and insects that rely on them.

“Where’s it going to go and where’s it going to end?” he said. “How many different kinds of pines is it going to attack?”