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A little beetle is causing big problems for Phoenix pine trees

By Lauren Gilger
Published: Tuesday, February 27, 2024 - 12:11pm
Updated: Tuesday, February 27, 2024 - 2:39pm

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If you’ve noticed a lot of the big, beautiful old pine trees around the Phoenix area turning brown and dying off, there's more than one reason why that's happening.

As The Show has reported before, it’s because of age and drought and our changing climate in the Valley but, it’s also because of a tiny brown beetle. 

Mitchell Lannan is forest health specialist for the Arizona Department of Forestry and Fire Management. Lannan told The Show this invasive insect is the only one in the state right now — but they’re worried about it’s spread. The main invasive insect tree pest is the Mediterranean pine engraver, otherwise known as MPE.

Fallen Aleppo pine tree in central Phoenix after a summer storm
Christina Estes/KJZZ
This 50-year-old Aleppo pine in central Phoenix was toppled by a summer storm in 2021.

Interview highlights

Tell us about this little bug. What does it look like? Is it a beetle?

LANNAN: Definitely. Yeah, it is a beetle and you're correct. It is very little. It is about 3 millimeters in length. So about the size of a grain of rice. This is a bark beetle, so it attacks trees. Specifically our ornamental Mediterranean pines that we have planted here in the Valley and also around Tucson.

So is this like why we are seeing some of those really big pine trees that have been around the Valley for a long time dying off? That's not just drought. It's also these guys?

LANNAN: Definitely, it, it's a lot of different factors and these, these MPE are one of those factors that are killing these trees.

So are you concerned about this beetle spreading further and the, the kind of further damage it might do here?

LANNAN: We are extremely concerned about that. Yes. So trapping that was done in 2023, so last year, found MPE to have spread to multiple new areas around the state. We found it in Superior. We found it in Pinetop-Lakeside, Kingman. Kind of all throughout the state in places where there aren't Mediterranean pines. So the new concern is that this, this pest is spreading to to native tree species.

Have you found any evidence of that happening yet, that it's harming other trees?

LANNAN: Not, not yet. There have been some, some lab studies done that show that these, these pests are able to attack some of our native tree species, our native evergreens. But we at the DFFM are working on a couple of projects to confirm that and confirm if they actually are at this point attacking those native trees.

So how does a little invasive species like this get here? ow do you find it? How does it come to Arizona when it's not from this place?

LANNAN: Definitely. These forest pests tend to spread through firewood and other woody material that's being transported from state to state. So often times it's, it's just people bringing firewood with them when they enter the state, and in that firewood are these little pests coming with them.

Is it surprising that we only have one invasive pest?

LANNAN: Definitely. I, I think that's really surprising, especially when you look at states like California or some of the Eastern states that have many, many forest or invasive forest pests. And I think it really has to do with the, the terrain around Arizona — having to go through many deserts to get to these, these areas like Phoenix.

eldarica pine
Steve McKelvey/Arizona Department of Forestry and Fire Management
Discolored needles on eldarica pine, a common sign a tree has been attacked by Mediterranean pine engraver beetles, according to the Arizona Department of Forestry and Fire Management.

So when you say people bring in firewood, is it usually just individual people who are going camping or is it often bigger manufacturers?

LANNAN: I think it's often times both of those situations. It's very hard to track where these insects are coming from, and we kind of just have to speculate. And, and we assume it's coming from both of those.

Is there anything being done to try to stop that from happening, at least on a commercial scale?

LANNAN: Definitely not really on a commercial scale. The Department of Agriculture here in Arizona does look at firewood and regulate firewood movement. And we try to put out a lot of different outreach materials to, to help people realize that that moving firewood is, is not so good. So the, the whole big slogan is "don't move firewood" or "buy it or you burn it."

Are there other invasive species that you're watching for that?

LANNAN: Yes, we have four big invasive forest pests that we are pretty concerned about at the moment. Those being the spongy moth, emerald ash borer, Asian longhorn beetle and the spotted lantern fly. So we've got several posters that, that kind of explain how to keep an eye out for these pests and what to look for.

I'll give an example of the emerald ash borer. This is a very brightly colored little beetle that attacks ash trees and olive trees — which we've got a lot of those planted on the Phoenix and Tucson area. So we're definitely concerned about it coming in. ... Right now they are in Colorado, in western Colorado. So they have been creeping closer and closer to the Arizona border.

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