Invasive Emerald Ash Borer Could Wipe Out Native Oregon Tree Species

0

A few weeks ago, Dominic Maze picked up his children from summer camp in a school parking lot in Forest Grove.

He arrived early. Rather than distracting herself with her cell phone, Maze got out of the car and began examining a nearby stand of ash trees. He noticed green shoots sticking out from the base of the trees. They looked “haggard,” he said.

“And then I just had a terrible sinking feeling in my stomach that I could look at an emerald ash borer infestation,” said Maze, who works as an invasive species biologist for the city of Portland.

The emerald ash borer was first detected in the United States in 2002, outside of Detroit, Michigan. The beetles have since killed hundreds of millions of ash trees, mostly in the Midwest and on the East Coast.

A D-shaped exit hole indicates an emerald ash borer infestation on an ash tree in Forest Grove, Ore.

Dominic Maze/Courtesy

Emerald ash borer larvae essentially eat a tree from the inside out, munching on the inner bark and limiting the plant’s ability to transport nutrients and water until the tree dies. . They emerge from the ash trees as metallic green beetles, leaving behind D-shaped marks.

Maze approached the trees and saw the alphabetical exit holes, he said, “and then I knew.” He was waiting for these insects, and they were finally here. This was the first detection of emerald ash borer west of Boulder, Colorado.

The effects on Oregon’s land, water and wildlife could be devastating.

“The emerald ash borer, like other North American ash species on the east coast, is expected to virtually wipe out up to 99% or more of Oregon’s ash from the landscape.” , said Maze.

The Oregon ash is one of 16 species of ash in North America and the only one native to the Pacific Northwest. The trees are most prevalent in the Willamette Valley west of the Cascades and along the Columbia River.

In an undated photo provided by the Minnesota Department of Natural Resources, an adult emerald ash borer is pictured.  The highly destructive insects that kill ash trees are metallic green and about 1/2 inch long.

In an undated photo provided by the Minnesota Department of Natural Resources, an adult emerald ash borer is pictured. The highly destructive insects that kill ash trees are metallic green and about 1/2 inch long.

Minnesota Department of Natural Resources/AP

Maze said Oregon ash trees are perhaps the most important species for bank stabilization and shade in tributaries of the Willamette River. The loss of these trees would likely result in increased stream temperatures and an associated decline in water quality.

Unlike many hardwood forests in the Midwest and East Coast, Maze said, Oregon doesn’t have many tree species that can replace ash in the event of mass mortality.

While ash species have built chemical defenses against native insects, they cannot stop the emerald ash borer, which is native to China, Japan and other Asian countries.

“The reason this particular insect is so problematic is that it has never been successfully eradicated,” said Christine Buhl, an entomologist with the Oregon Department of Forestry. “Due to its biology and the way it spreads, it has proven virtually impossible to eradicate.”

So far, the state has not confirmed any established emerald ash borer colonies outside of the Forest Grove stand.

Slow the spread

The late arrival of the beetles, about 20 years after they were first detected in the United States, allowed Oregon to plan ahead.

Some municipalities like Portland have banned the planting of ash trees as street trees, for example. The state has also harvested and stored nearly one million Oregon ash seeds to try to preserve the species’ genetic diversity for replanting.

In this file photo from October 26, 2011, an emerald ash borer larva is removed from an ash tree in Saugerties, NY. The emerald ash borer, first discovered in 2002 in Michigan, is now present in 30 States and has killed hundreds of millions of ash trees.  Forests from New England to the West Coast are threatened by invasive pests that defoliate and kill trees.  Scientists said the pests are pushing some tree species towards extinction and causing billions of dollars in damage a year.

In this file photo from October 26, 2011, an emerald ash borer larva is removed from an ash tree in Saugerties, NY. The emerald ash borer, first discovered in 2002 in Michigan, is now present in 30 States and has killed hundreds of millions of ash trees. Forests from New England to the West Coast are threatened by invasive pests that defoliate and kill trees. Scientists said the pests are pushing some tree species towards extinction and causing billions of dollars in damage a year.

Mike Groll/AP

Buhl said slowing the spread of the emerald ash borer is the only tool the state has to potentially save Oregon’s pockets of ash.

“Slowing the spread buys us time,” Buhl said. “We don’t have time to preventively remove all the ashes and replace them with other trees. We need time to act and slowing the spread is essential for that.

She said Oregonians first need to be able to identify an ash tree and then understand the signs of a possible infestation. D-shaped exit holes, basal shoots, dead treetops and S-shaped patterns under the bark where the larvae feed on are visible symptoms. Brilliant green adults are also common on infected trees in summer.

People who think they have identified an emerald ash borer infestation can report it to the Oregon Invasive Species Council’s hotline online or by calling 1-866-INVADER. Know what emerald ash borers look like before reporting, Buhl said, because there are many similar-looking insects.

The state also recommends people avoid carrying firewood, which can carry emerald ash borers and larvae from place to place.

Share.

Comments are closed.