(chainsaw buzzing) - [Narrator] There's a tree killer on the loose in Oregon (tree trunk thuds) and nobody knows how to stop it.

(wood creaking) It's an invasive green beetle called the emerald ash borer.

It came to the Midwest from Asia in 2002, and it's been on a killing spree ever since.

- [Matt] It's been in the East coast over 30 years and it's killed over a hundred million ash trees.

- [Narrator] Now it's killing ash trees in Oregon.

- They're basically sitting ducks.

There's nothing that can stop emerald ash borer from coming through.

We can only slow it down.

- This is an ash tree and they're going to have compound leaves.

So this is a leaf.

The whole thing is a leaf.

- Ash is a beautiful tree.

Unfortunately emerald ash borer will kill the vast majority of the ash in Oregon, and it's going to be a lot of work for everyone.

(spray paint hissing) - [Narrator] Is there any hope?

The answer to that is maybe.

- [Dominic] Cyrene and Zane, can you guys find a stump here from those trees?

- [Zane] Yeah.

- [Cyrene] Oh, dad, there's a stump.

- [Dominic] Oh yeah.

Very good - [Narrator] Biologist Dominic Maze and his kids were the first ones to notice that Oregon's ash trees were in serious trouble.

- [Zane] And heres one right here too.

Here's one.

- So I was just looking around.

I always like looking at these swales- - [Narrator] In the summer of 2022, Dominic was waiting at Joseph Gale Elementary School in Forest Grove to pick up his kids.

- I noticed within the parking lot there was a stand of very poor looking ash trees.

All of them dying.

And I thought, "Boy, that looks really bad."

And then just getting a real sinking feeling in the pit of my stomach.

- [Narrator] He asked the kids to look around for a little green beetle, and they found one.

- I was just going like this, and it landed in my hand.

- [Narrator] How big was it?

- It's like very tiny about like that big.

- No, no, it's not that big.

- No.

- Say it.

- It's about that big.

- No, it's not that.

- [Dominic] I think it's probably about halfway between those two estimates.

- [Narrator] These were the first Oregon trees to be diagnosed as infested with emerald ash borer.

And they were cut down.

- And you come down here, you can actually see exit holes.

This tree was heavily infested, and that was the start of what we knew was going to happen, emerald ash borer reaching Oregon.

A very depressing story that's about to play out in the Willamette Valley, and it is like a death sentence.

When you're an invasive species biologist, much of nature's ruined for you.

You see along here, the blackberry, the exotic hawthorns.

Once the ash canopy dies, we expect these type of species to just take off.

Once that canopy's gone of Oregon ash over there.

This is a purple prism sticky trap.

And it'll tell us if emerald ash borer is here or not.

- [Narrator] The beetle hasn't made it to ash trees in the city of Portland yet, as far as we know.

But Dominic is on the lookout.

- So these traps have a sticky outside, and I'll be sticking a lure, a chemical lure on the inside.

- [Narrator] He's most worried about the habitat along rivers and creeks, where native Oregon ash trees have a unique ability to provide shady streamside habitat.

- When we lose that Oregon ash, we lose that shade.

We lose that habitat.

And that shade is critical for keeping water cool.

And who likes cool water?

All of our salmon species that pass through the city of Portland or rear their young here.

- [Narrator] And there's really no other tree species that can fully replace it when it dies.

- [Dominic] Only Oregon ash can grow in the wettest, muckiest organic soil systems in the Willamette Valley.

- [Narrator] That's probably why so many Oregon rivers are lined with this native tree.

Other trees, like cottonwood and willow, can't thrive in the same conditions.

- This habitat is irreplaceable.

The emerald ash borer represents a forest pest worst case scenario right now.

Loss of this irreplaceable keystone species.

And we're not going to see any native trees replace it in many settings.

It's going to be bad.

- [Narrator] In April of 2024, dozens of trees infested with emerald ash borer beetles were removed from Forest Grove, and the wood was chipped up or burned to destroy the beetle larva.

That was just one part of an elaborate strategy to slow the spread of this invasive beetle.

Here's another tactic.

On the outskirts of that infestation, state workers created trap trees by girdling them.

The dying tree sends out a distress signal that will attract any beetles nearby.

- All set.

- [Narrator] Later, the girdled trap trees are removed and workers with the Oregon Department of Agriculture peel back the bark to see how many beetle larva they can find.

- I'm just kind of like going slow.

So, oh, there's a larva.

So this is how they're killing the trees as they're eating through and cutting off the flow of nutrients and water up the tree.

All that area around the gallery is starting to die.

- [Narrator] The larvae feed in galleries like this before they turn into beetles - It will overwinter in that pupal chamber.

And then when spring comes around, it'll pupate into adult and chew its way out and take off.

- [Narrator] In August of 2024, another beetle infestation was discovered near Woodburn.

in Marion County.

Max Ragozzino with the Oregon Department of Agriculture checks the trees for beetle damage.

- [Max] Yep.

D-shaped exit holes.

Oh.

- [Narrator] INside the tree bark, he finds the culprit.

- [Max] See the shining green?

It's the beetle's abdomen.

- [Narrator] This beetle didn't make it out, but a lot of others did.

- So yeah, all of those galleries are from the emerald ash borer.

There's a lot over here.

Boom, boom, boom, boom.

Boom.

That is a telltale sign.

Each one of those indicates one beetle.

Unfortunately, I think this is the potentially the heaviest infestation of emerald ash borer in Oregon.

EAB has probably been here for many years.

If they're not dead, most of these trees, they're not long for this world.

- [Narrator] Invested trees will often have splits in their bark and fresh branches growing out of the trunk.

The last gasp from a dying tree.

- So I think there's going to be more of those- - [Narrator] Max is working on yet another strategy for slowing these beetles down.

It's called a bio control.

- These are the largest of our parasitoid wasps that we'll be releasing today.

- These little wasps lay their eggs in the emerald ash borer larvae.

Their antenna can actually sense where the beetle larvae are chewing under the bark.

- [Max] We're going to go for the trunk here.

Sometimes you just got to encourage 'em a little to leave the cup.

- The parasitoid wasps don't just live off their hosts like parasites.

They kill the beetle larvae by feeding on them.

- [Max] Few stragglers.

- [Narrator] But don't worry, they don't sting people.

In fact, they don't have stingers at all.

- Nature will know what to do from here.

(drill buzzing) - [Narrator] Here's another way to slow down the emerald ash borer.

Laura Trunk is injecting this tree with pesticides that will kill emerald ash borer beetle larva for the next two or three years.

- [Laura] I'm going to pump a little basically to push that chemical through.

That will get uptaken right into the cambium layer of the tree.

- [Narrator] It's one of 360 ash trees she's planning to treat to protect them from the invasion.

- These are our extremely large, beautiful Oregon ash trees.

They are hundreds of years old.

If this is lost, we cannot duplicate this for a couple hundred years.

So it's worth protecting and keeping on site.

As long as I am here, they will get treated.

- [Narrator] She spent her whole career restoring the ash-dominated habitat at Jackson Bottom Wetlands in Hillsboro.

Now, the site is home to thousands of ash trees facing near certain death.

She can't treat them all with pesticides.

It's far too labor-intensive.

- [Laura] It can get very difficult to be able to treat all these trees.

- [Narrator] Statewide, we can only hope to treat a relatively small number of trees.

- It's very sad what is coming.

I have spent the last 16 years restoring Jackson Bottom.

We've been removing invasive species for decades.

We have built wetlands.

We have put in a massive amount of effort into bringing this place back.

And losing the trees is going to be very difficult and is basically, we're going to have to start the restoration over.

- [Narrator] The ash borer hasn't made it here yet.

And her goal right now is to beat it to the punch.

She's opting to kill some of these ash trees before the beetles can do it, with a crew of arborists.

- [Arborist] So we got 210, which we'll do tomorrow too.

- You know, I work out here every day, so I look and I'm like, "That tree's going to be dead.

That tree's going to be dead."

Okay, like a lot of these trees are going to be dead.

As these trees fall, these trees will fall on the trails.

These trees will be hazardous for people.

- [Narrator] She's making plans to remove, prune, or treat every ash tree on the property.

We all, and she's planting new species to replace them.

- So you can see, here's another one of our little oak trees here.

We've actually gone through and probably cut down about 200 ash trees, this diameter, they were about 10 feet tall, all in preparation for replanting.

- [Arborist] Beautiful.

- [Narrator] Some of the bigger ash trees will be toppled and left on the ground.

Others shall leave as snags for birds to nest in.

- Nice.

- That is a habitat snag.

- That is a habitat snag.

Yeah, it's ambitious, but this is the correct course of action, like trying to use the trees for wildlife, starting to replant now before we lose all the trees.

This is not easy for us.

Especially not easy for me.

I've been here for over 16 years.

I've watched this site grow and change and wildlife species basically skyrocket.

So to lose these trees, it's devastating.

- [Narrator] But all this work will create a stronger, more diverse forest.

- [Laura] If a new pest comes in and attacks one more tree species, we'll have other species to be able to fill in.

Right now we just have ash, so when we lose it, we'll have nothing.

Hopefully, by the end of this, we'll have a more stable, self-sustaining forested habitat with a lot more species, so we don't go through this again.

(tree creaking) (tree trunk thuds) - [Narrator] There's at least one small glimmer of hope for Oregon's ash trees.

They didn't evolve with emerald ash borer beetles from Asia, so they never developed any defenses against them.

But at the Dorena Genetic Resource Center, scientists Richard Sniezko and Glen Howe are looking for any ash trees that have natural resistance to the beetle so they can survive this pest.

- And then when these are planted out, we keep track of every tree.

- I probably collected 10 or 15,000 seed from individual trees.

- [Narrator] They're collecting seeds and planting test plots.

- And when the emerald ash borer moves into this area, this will be a test to see if there's resistance.

If there is some resistance, but- - [Narrator] Maybe they'll find some survivors that have genetic defenses against the emerald ash borer, so we don't have to say goodbye to Oregon ash forever.

- Most of our ash currently on the landscape are doomed.

But can we get ash back 20, 30, 40 years down the line?

I want to know, can I solve the problem and get the trees out there for future generations?

- [Narrator] The Oregon Department of Forestry is tracking the spread of the beetle with hundreds of purple sticky traps.

- [Wyatt] All of these are cooperators that are putting traps up.

- [Narrator] Oregonians can help by checking ash trees for signs of beetle damage.

Look to see if the top of the tree is not producing leaves like it should.

Then check the bark on the trunk for holes like this.

- Emerald ash borer makes these characteristic D-shaped exit holes when it leaves the tree.

And so no other insect will do that in ash trees.

- [Narrator] You can report infested ash trees on this website.

And to help slow the spread of the beetle, experts say, be sure to buy your firewood where you plan to burn it.

Please don't move it more than 10 miles.

That's likely how the beetle got here in the first place.

- Great people just doing their thing in their own Northwest-y way.

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