GEARHART — Large Sitka spruce trees in the yard were one of the selling points when Angela Sidlo and her husband decided to buy a house in Gearhart a few years ago. Now, with their green needles suddenly brown, the trees look like they are dying.
Sidlo, a holistic health practitioner, isn’t the only one seeing disturbing changes in trees known as evergreen.
Up and down the North Coast, spruce trees are turning brown — “red,” if you’re a forester, because the same issue is happening on commercial timberlands, too.
A tiny green bug is likely to blame.
Several years of unusually mild winters and drier springs have set a perfect stage for spruce aphids. Without hard frosts and wintry weather, the insects boomed.
The aphids are not usually associated with widespread tree death. But Luke Colvin, a certified arborist and owner of Arbor Care Tree Specialists in Astoria, took down two trees for clients this spring and expects more will follow.
He is used to seeing aphid populations flare up every few years, but it has been bad for several years now. And the aphids are hitting at a time when trees are already stressed. Drought conditions over the past three summers have weakened trees that would normally be able to withstand an infestation.
This year, Colvin said, “is significantly the worst I’ve ever seen it.”
Spruce aphids — “soft-bodied insects with piercing-sucking mouthparts,” according to the horror-movie description from Oregon State University — look similar to the lime-green aphids people see on their rose bushes. They are an invasive species and range on the West Coast from California to Alaska.
Clatsop County’s spruce trees may look terrible now, but there is good news. If a tree is not too far gone, it can be saved or even recover on its own.
This week, Colvin sent out a mass email to Arbor Care clients with information about what might be happening to their spruce trees. Gearhart City Manager Chad Sweet, who was noticing issues with trees around the city, posted the information on the city’s website.
The men are concerned people will want to start removing infested trees prematurely, believing the trees are dying or already dead.
The aphids mass in colonies on spruce tree species and feed on sap in the needles. Infestations can be most severe on the Sitka spruce, a coastal tree, according to the Oregon Department of Forestry.
As the aphids feed, a tree’s needles turn from green to yellow, then to a rusty brown. Entire branches of a tree might die. The damage isn’t usually apparent until the aphids have already moved on.
An infestation may cause banks of older needles to drop prematurely, but aphids typically leave buds — the soft, bright green tips that signal new growth and appear on spruce trees in May and June — alone.
Gearhart plans to work with an arborist to nurture impacted trees in parks, along street right of ways, by Neacoxie Creek and along the city’s Ridge Path Trail.
“We want to protect (the trees) as best we can,” Sweet said. “They’re a big part of Gearhart.”
The best way to treat infested trees is to take action long before aphids ever show up. For now, Colvin recommends boosting the health of trees by watering them during the summer months. Soaps can be used to slough aphids off young saplings, but will not work for large trees or commercial stands.
The most effective way to inoculate trees is to use insecticides, which is not an ethical option when bees are active, Colvin said. Insecticide treatments need to wait until the fall.
A difficult conundrum
It’s a difficult conundrum for people concerned about insecticides, Colvin admitted, but there are no real effective biological means to control spruce aphids.
“So do you want to stick to your guns of no pesticides ever and let a huge percentage of the large, historic Sitka spruce die because of it? It’s kind of a toss-up,” he said. “What do you do?”
People who opt for insecticides should make sure they’re working with someone who is specifically licensed to use the product, he added.
The Sidlos asked Colvin to take a look at the trees in their yard Wednesday. They aren’t sure what they want to do about the aphids he found. The health of nearby Neacoxie Creek is important to them, Angela Sidlo said. She is contemplating what other trees they could plant if the spruce do not recover or continue to suffer from aphid infestations.
“To tell you the truth, we’re kind of lacking in our management options in terms of what to do,” said David Shaw, a professor at Oregon State University.
Spruce aphid population booms detonate in the winter and early spring — at times when there are few insect predators like yellow jackets or wasps around to keep their numbers in check.
Shaw, who is based in Corvallis, has been in contact with GreenWood Resources about issues the forestry giant is seeing on timber holdings in Clatsop County and elsewhere. He hopes to make a trip north soon to conduct his own investigations.
“With the symptoms we’re seeing, I’m confused whether it’s something in addition to spruce aphid that’s happening, particularly something associated with the drought we had in 2018,” he said.
Clatsop and Columbia counties, as well as a large portion of Tillamook County, are abnormally dry right now, according to the U.S. Drought Monitor.
Like Colvin, Mark Morgans, area manager of GreenWood’s Lewis & Clark Timberlands, is concerned about what his foresters are seeing. But he’s not ready to start waving red flags.
Aphids have come in cycles before and GreenWood is hoping to weather this one, too.
Sitka spruce timber is considered a lower-value product, but it has become a desirable species for export in the past decade. The aphids are banqueting on important needle banks the trees use to capture sunlight and store carbon. Trees hit heavily by the insects may end up stunted.
But the aphids are nearing the end of what is usually their active stage, Morgans noted. If there is any silver lining, it’s that the aphids dined on last year’s growth. The trees are putting on new growth now.
The spruce GreenWood has used to replant harvested stands for the past decade were intended to withstand onslaughts from a different insect pest. These trees appear to be more resistant to spruce aphids, as well.
Foresters are looking at how increased sunlight in stands might create less desirable environments for aphids. They are considering heavier thinning work on young spruce stands.
The timber company replants with a diverse mix of tree species to mimic historic forests, a move that means entire stands aren’t wiped out when pests like spruce aphids show up.
For now, aphid issues on the timberland appear to be limited to pockets along highway corridors and at lower elevations, said Kathryn Olson, an area forester with GreenWood. Foresters first started noticing brown Sitka spruce several weeks ago in stands near Cannon Beach.
“At this point, our main goal is to monitor the extent, so we know and we can watch it,” Olson said.
Up until this year, Colvin would have said humans are the usual culprits when it comes to threats to trees. Construction and development can compact tree root zones or restrict a tree’s ability to access water. Installing underground utilities can sever tree roots.
“Humans are by far the worst infestation for trees,” Colvin said. “Urban human activity is the No. 1 cause of tree death.”
And now? “Maybe the aphids felt left out.”