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Texas forests threatened by spread of invasive beetle

U.S. Fish and Wildlife Service

Small green beetles called emerald ash borers have steadily decimated forests across the United States for more than two decades. Emerald ash borers are invasive, and as their name suggests, make their home in various species of ash trees.

The beetles were first found in Texas in 2016. Recently, however, the Texas A&M Forest Service announced that they’d been located in five new counties in Texas.

Demian Gomez, a regional forest health coordinator for the Texas A&M Forest Service, spoke with Texas Standard about emerald ash borers’ impact here so far. Listen to the interview above or read the transcript below.

This transcript has been edited lightly for clarity:

Texas Standard: This area where emerald ash borers have been recently discovered includes five counties roughly between Fort Worth and Waco. How do you know they’re there now? 

Demian Gomez: Well, for the last several years, the Texas A&M Forest Service has been conducting monitoring for this pest. And that is basically around 500 traps that we deploy across the state to actually try to figure out how this insect is spreading.

But we also work with multiple municipalities, agencies, landowners to provide trainings and resources for them to be able to early detect these species throughout the range and how it’s actually moving. So, these different counties has been a result of a different network of collaborators, but also the work that we do together to try to monitor for the pest.

How big of an impact have emerald ash borers made in Texas so far?

Yeah, it’s a very significant impact since it was first introduced. Of course we’re talking about ecological impacts. And that has to do with a species that is basically wiping out ash trees from the North American continent.

You know, the way it’s basically affecting forest communities, it’s affecting insects, it’s affecting birds. There are hundreds of insects that actually rely on these species for basically feeding, but also as a resource for reproduction or different things. So, the ecological impacts have been very, very significant.

The urban environment, as well. Cities have been impacted just because trees are a very important resource in terms of adding thousands of dollars for property values. They decrease cooling cost. They have a major role in stormwater capture and things like that.

So the ecological impacts, the impacts that it has done to different cities, the economic impact as well… We’re talking about removal costs. We’re talking about treatments. We’re talking about potential property damage. Those are millions of dollars that are going to accumulate throughout the years.

» BEWARE THE EMERALD ASH BORER: Hear from our resident insect expert, Wizzie Brown, on the invasive species

So they only like ash trees. Which trees specifically are we talking about? And what do they do? Eat them from the inside out?

Yeah. So, they feed basically on all species within the genus Fraxinus. That’s one of the most, widely distributed tree genera in North America. So, every ash tree is basically affected.

An emerald ash borer is what we call a “primary pest.” That means that it doesn’t really matter if the tree’s stressed or not. They’re just going to go after every ash tree out there. And the way that works is the adults are going to feed on the leaves, but the main part of the damage is created by the larvae.

So adults are going to find little cracks on the bark. They’re going to lay their eggs, and then the larvae is going to start boring inside the trunk, under the bark. And they’re going to feed on the vascular tissue – what we call the phloem, the cambium. Those are parts of the tree that actually move nutrients throughout the tree. And when you start eating on that and you start destroying that vascular tissue, what happens is that you girdle the whole tree.

Basically it is cutting the flow of nutrients, and the tree ends up dying. So it’s very common to see things like dieback or the canopy start dying. Big limbs start dying, and then, that usually ends up in mortality.

Well, you mentioned traps, but that’s really for identification. Is there anything that people can do to slow the spread?

Yeah. So management for this insect has many different aspects.

The first one is early identification. We want to make sure that our partners and folks out there are able to recognize when an ash tree is dying from ash borer. And they have some very specific things that they do.

The squiggly, S-shaped lines left by the emerald ash borer beetles in the bark of trees it’s infected.
U.S. Fish and Wildlife Service
The squiggly, S-shaped lines left by the emerald ash borer beetles in the bark of trees it’s infected.

Under the bark, they’re going to produce these S-shaped galleries or like a gallery in zigzag, which are basically the tunnels that the larvae are doing. But when the adults emerge from that tree, they’re going to leave like a V-shaped exit hole, which is pretty characteristic as well.

But then the next step is once the tree is infected, we want to make sure that that tree is destroyed before the adult leaves that tree. And that will be cutting it down, either keeping it, burning it, burying are something that we can do, depending on the circumstances, of course.

But there are also treatments to protect high quality trees, right? Things like injecting the tree with an insecticide that will last a couple of years. So that way your tree in your front yard will not be affected when it’s a high quality tree.

And another thing that’s important – and this not only applies to emerald ash borer, but it’s usually the case for many invasive wood borers – is that we want to be very careful about firewood, right? The reason why these things kind of like get established into new regions and keep spreading is because people buy firewood or collect firewood and then move it to a different state or a different county. And basically they don’t know that that wood has been infected with ash borer.

When the beetles emerge, they’re in a new region, in a new area. And that’s why this insect has been popping up in states where they’re not really close to what we would expect. It showed up in Colorado, it showed up in Oregon, it showed up in Texas. And, you know, it was at the beginning kind of like far from other infestations that we were aware of.

So basically, in terms of firewood, if you go camping, if you, have property, buy it and burn it in that same spot or collect it and burn in the same place.

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