The Christmas tree-sized Sitka spruce behind the GreenWood Resources office in Seaside was so infested with spruce aphids last year it looked like it was moving all on its own.
But Christine Buhl, a forest entomologist with the Oregon Department of Forestry, and David Shaw, a professor at Oregon State University, found only a few spruce aphids when they checked the tree last week.
The young tree’s most recent growth of needles looked stunted, but small buds were just beginning to swell at the branch tips — a good sign after a major outbreak threatened Sitka spruce last year.
“They’re here, but it’s nothing to write home about,” Shaw said after looking at other trees on the timber company’s property. Maybe, he suggested, the outbreak is winding down.
Buhl hopes to collect more data, working with state and private timber representatives to document damage to trees. She plans to coordinate with Dan Stark, of the Oregon State University Extension Forestry in Astoria, to train citizen scientists to locate and log information about spruce trees on the North Coast.
Despite the potential for spruce aphids to impact a large number of trees, little is known about their full life cycle in Oregon or how much abuse trees can ultimately withstand and still thrive.
Aphid infestations usually boom and then bust. The first year is bad, Buhl said. But by the second year, populations decline and by the third year, they’re hardly noticeable.
Buhl’s instinct is to be cautious, though, going into the second year of the recent outbreak. Despite a flush of warm weather this month that would make her expect to find more aphids, it may be too early in the season to say how things will go this year.
Last year’s outbreak affected more than 7,000 acres statewide, with some of the worst patches concentrated on the coast. Trees that should have been evergreen were brown or red and shedding their needles at an alarming rate. When arborists and experts like Buhl took a closer look, they found the branches were crawling with spruce aphids, a tiny pest that feeds on the sap in tree needles.
City officials in Gearhart worried about the health of legacy trees, while homeowners juggled the pros and cons of leaving trees that looked dead standing in their yards. Advice from the state and local arborists was to wait and see. The pests were another hit to trees already stressed by a string of unusually dry summers.
For some, it was a taste of what may be on the horizon as climate patterns shift.
This year, foresters at GreenWood Resources are looking at whether they need to incorporate growth reduction into their models, accounting for spruce whose growth will be stunted by spruce aphids.
Oregon State Parks officials worry about spruce trees in Cape Lookout State Park farther south that are being battered by spruce aphids, as well as salt water intrusion. They are worried about the possibility of aphids landing on the massive Octopus Tree in Cape Meares, a Sitka spruce estimated to be nearly 300 years old.
Arbor Care Tree Specialists, based in Astoria, treated numerous spruce trees for clients last spring. They erred on the side of caution when it came to removing trees, taking down only trees that had no live foliage left, Luke Colvin, the company’s owner, said.
Now, they are waiting to see what this year will bring. On Colvin’s mind are the trees they left standing that had very few needles.
“If we have even a medium-size outbreak ... a lot of those trees are going to die,” he predicted.
Several years of mild winters on the coast have set a perfect stage for a spruce aphid boom. Still, Oregon’s forests have rebounded from far worse outbreaks. In 1986, spruce aphids hit more than 127,000 acres in the state.
Conditions are different now, Buhl said, but she expects many trees will rebound. She pointed to a tree on GreenWood’s property that was more brown than green, then noted the bright green tips breaking out at branch ends. New growth.
For now, she’s sticking to her message from last year: “Ride it out.”