- [Narrator] For Richard Sniezko, the scenic rim of Crater Lake is also a battleground.

- This is a white bark pine, and it's right on the rim of Crater Lake.

and you can see this branch has a major canker from the white pine blister rust disease.

- [Narrator] He's fighting to save these trees from an invasive fungus called blister rust that came from Europe.

- Well, here's another one, so geez.

There's one, there's one, there's one, there's one, there's one.

They will grow down to the stem of the tree and infect it stem of the tree.

They will then girdle the tree, and they can kill the tree.

Those spores are orange and so it looks like a blister, and so it's called blister rust.

- [Narrator] The white bark pine trees at Crater Lake National Park are iconic.

(wind whooshing) They're one of the only tree species built to survive the harsh conditions on what's left of Mount Mazama.

And Richard is on a decades-long quest to keep them there.

- We're kind of the triage.

We've got to fix the problem, so to me, it's a puzzle.

This will be another one that we're following.

And people who know me, I leave kind of no stone unturned.

- [Narrator] The threat of blister rust is nothing new for Crater Lake National Park.

Field Guide detailed the problem way back in 2002.

- [Narrator 2] Park ecologist, Dr.

Michael Murray says, small warts on white bark pine trees are as deadly as chainsaws.

- [Michael] The way I see it right now, the extinction of white bark pine in the park is imminent.

I expect us to lose about 90 percent of the white bark pine in this park at least.

- [Narrator 2] Unfortunately, there's nothing anyone on the park staff can do to stop trees from dying.

- There's no doubt that we're being beat here (sighing) - [Narrator] Back then, the outlook was bleak, but not everyone believed there was nothing they could do.

You can see a young Richard testing a possible solution by intentionally infecting young pines with the blister rust fungus.

- [Richard] We collect leaves of currants and gooseberries from the wild that are infected with the disease of the blister rust.

These are the spores that will be dropping on the pines that will infect the pine trees.

- [Narrator] So now, more than 20 years later, we're checking up on this problem.

Are the trees surrounding Crater Lake still doomed?

- [Richard] This is one that shows the orange.

- [Narrator] First off, the work really hasn't changed.

(crew chattering) - Richard still grows lots of white bark pine trees in the same greenhouse using seeds collected from the forest.

(plastic crinkling) - Ready?

- [Narrator] Then he tries to kill them.

(nozzles hissing) - [Richard] This fog chamber provides the optimal environment for the disease to progress, for the spores to fall and infect the pine.

Yeah, we'll go down here first.

- [Narrator] Richard then watches the trees for years to see how they respond to blister rust infection.

- This is white bark pine.

What you're gonna see now is which seedlings have cankers and which ones have needle spots, and which ones don't have cankers.

This one probably has about 10 different cankers on it.

There's a canker, there's a canker, canker, canker, canker.

Probably in three months, the oldest cankers will grow together, and then next spring or summer, the seedling will die.

Within a year, we know the most susceptible ones, okay, 'cause they're usually 100% cankered, they will start to die soon after that.

But just looking over here, you can see massive mortality from blister rust.

- [Narrator] But not all of the trees die.

- [Richard] And our best white bark pine might have seven survivors left out of 10.

- [Narrator] At this point, he's grown tens of thousands of trees from forests across Oregon, Washington, and California to test them for genetic resistance to blister rust, and he's found quite a few survivors.

- As we started seeing the level of resistance there, I think that surprised almost everybody.

- [Narrator] The growing a forest of surviving trees requires some extra work.

These tree climbers are part of a plan to cross-breed the surviving trees.

- [Tree Climber] You like it, Evan?

- [Narrator] Testing shows this tree and its offspring- - All right, you're on.

- [Narrator] Can survive blister rust infection.

So tree climbers scale the tree to pollinate it with pollen from other resistant trees.

- [Tree Climber] Slide this right through where your carabiner is.

- Right there?

- Yeah.

- [Narrator] They cage the pine cones to keep them from getting eaten by birds.

(bird chirping) The Clark's nutcracker depends on eating their seeds.

They collect the resulting cones to grow more seedlings.

(needles crackling) - Got all their cones still in cages.

These are the first crosses made out in the wild in Oregon and Washington between two resistant trees of white bark pine, and you can actually see a seed in there.

- All right, so this is a good spot right here.

You can see it growing here just fine.

So we chose this, we would go down further, but it's too dangerous.

This is the spot.

(shovel thudding) - [Narrator] Thousands of the surviving seedlings have been planted on the landscape over the last 10 years.

Park biologist, Thomas Allen, is tasked with planting 600 of them this year.

White bark pine is critical to the ecosystem at Crater Lake National Park, and these trees are still in decline.

(shovel thudding) The park staff hope to plant enough new resistant trees that they'll replace the older trees as they die.

- Hopefully it grows up to live many hundreds of years.

It's exciting, you know, trial and error.

Some days it's one step forward, two steps back, but then we can have these little aha moments and say, "Well, this is working."

It's a hope.

- [Narrator] This ancient pine is known as the Grandmother Tree.

- You can only estimate just how old it is, how majestic it is.

I'm thinking 6 to 800 years.

It's so beautiful, we don't want to see it go.

We see no signs of blister rust here.

I mean, it's just a grand, old lady.

- [Narrator] Thomas says this is the future he wants for the trees he's planting.

These resistant trees were planted in 2009.

They're part of a future forest that's more likely to withstand the blister rust invasion.

- I think there's 302 trees that were planted here, and there's now something like 76% survival.

- [Thomas] A lot of them are holding on and looking good.

- [Narrator] Richard and park staff are still watching these trees and learning from them, especially when they get infected.

- How many of these will survive over time?

And so we have an expectation, but out in the wild, it could be completely different, and it could happen over 20 or 30 years if this is happening.

So it's not something that you have the results in five years.

- [Narrator] White bark pine was listed as a threatened species in 2023, and other threats still loom for them, especially in a warming climate with declining snowpack - like the mountain pine beetle that killed this tree.

- And if we go over here... - But thanks to decades of genetics work by researchers like Richard, they're no longer facing imminent extinction, here at Crater Lake National Park or across the Northwest.

- Blister rust, in many areas, will be more a minor nuisance rather than a major problem that threatens the existence of the species.

It's gratifying to have that type of accomplishment.

You can say, "Hey, you solved the blister rust problem."

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