Arizona Researchers: Fungus Could Be Key To Slowing Destructive Bark Beetles

By Andrew Bernier
Published: Wednesday, April 15, 2015 - 8:50am
Updated: Wednesday, April 15, 2015 - 10:20am
Audio icon Download mp3 (5.53 MB)
(Photo by Andrew Bernier - KJZZ)
A petri dish with the Beauveria fungus growing. Behind it is borings of bark beetle.
(Photo by Andrew Bernier - KJZZ)
If you've gone hiking and seen sticks or logs like this, bark beetles were once, and may still be present.
(Photo by Andrew Bernier - KJZZ)
Dr. Rich Hofstetter inspects test logs sprayed with the fungus before the winter.
(Photo by Andrew Bernier - KJZZ)
The orange pulp chewings left behind by ips and bark beetles after boring into wood.
(Photo by Andrew Bernier - KJZZ)
Hofstetter and Bradley standing beside a large pile of recently cut trees, prime breeding ground for bark beetle.

Growing bark beetle populations have decimated forests in the western United States, with some damage to  northern and eastern Arizona forests. But local research is getting closer to a “solution” that may help.

In the Arizona ponderosa pines, academic, industry and government researchers are teaming up to combat bark beetles. Rich Hofstetter, a Northern Arizona University forestry researcher, said the trees can be hardy, to a point.

“Some of these larger trees can survive a large number of attacks," Hofstetter said. "And it’s only in drought times where that is not the case. And that’s really the only time in Arizona that we see significant problems in our ponderosa.”

Beetle populations are growing thanks to a perfect storm of conditions. Warming climate has decreased the duration of freezing temperatures to kill larvae. Fire suppression has increased the number of trees. Add in persistent drought and proximity to vulnerable trees, beetles have little trouble eating their way through large patches of forest.

Researchers approach a pile of small logs sprayed with a fungal solution last November that the team is testing for beetle mortality.

“We want something very simple to work with," said Hofstetter. "Easy to cut up, spray and then you don’t need a lot of beetles to kill the tree either, so this is an 'ips' hit here.”

Ips is a shortened latin nickname for another species of wood-boring insects. Orange pulp piles between the bark, the leftover chewings of the beetle.

Researchers with Montana BioAgriculture, a commercial research company, are also working on the project. Cliff Bradley with Montana BioAgriculture hopes when the log goes to the lab, it reveals dead beetles, meaning the fungal spores lasted through the winter.

“We coat these logs with spores," said Bradley. "There’s 10 million — give or take — per square centimeter on there. And then the beetle picks up the spores when it lands and looks for a place to bore in. It gets infected and dies.”

Bark beetles bore into tissue under the bark that carries sugar from leaves to the rest of the tree. They lay eggs in tunnels that sever the tissue, eventually killing the tree. While ips favor recently fallen trees, Dendroctonus beetles can attack live trees, especially ones under stress.

“If we can find one fungus that could kill the Dendroctonus, maybe another one that would kill ips," Bradley said. "In an ideal world, we would find one that would kill both.”

Naturally occurring in forests, the fungus has about a 90-percent mortality rate. Starting with 30 fungus strands, the team is looking for one or two to mass produce.

Using a commercial sprayer with increased pressure, the mostly water-based solution can reach up to nearly 40 feet, enough to cover most smaller diameter trees. While chemical sprays are already being used commercially, Monica Gaylord with the United States Forest Service said those need to be applied from the top down, which sometimes can’t happen.

“It can only be done in areas where you have good access," said Gaylord. "A lot of times you need a cherry picker or a really high powered sprayer, and it’s cost prohibitive, too.”


Gaylord said there is often increased beetle activity after forest fires. So while the spray is a welcomed tool, the forest service needs to continue with thinning projects.

 “A lof of the thinning that we do for fires also helps for bark beetles," Gaylord said. "So, a thinned forest is more resilient.”

Farther into the forest, active thinning is taking place. Massive piles of fresh trees, large and small, are scattered, often under large healthy trees with deep tire tracks having torn up the ground below. Hofstetter said large piles trap moisture, attracting and breeding more beetles.

“So predators will pile into these but what happens is they’ll come and burn these in a year, the ips have all left, but the predators are still in there, and they die," Hofstetter said. "I always tell people either burn right away, when the ips are in, or wait three years so all the natural enemies come out.”

But looking at the large, healthy tree looming over the pile, Bradley thinks waiting is a bad idea.

“By the time a pile this size has dried out for three years, you’re going to make a hell of a torch" said Bradley. “Flames 30 to 40 feet in the air.”

“That’s what we said, that tree would be dead," Hofstetter said. "Yeah, this is, this is too big.”

But if the piles were smaller and sprayed as they were stacked, the researchers argue burns would be much safer and the beetles would have much less material to call home.

If you like this story, Donate Now!

Like Arizona Science Desk on Facebook