Alien Species: Emerald Ash Borer
This Exotic Wood Boring Pest Is An Invasive Insect Plaguing Ash Trees And Potentially Being Spread Via The Transport Of Firewood Internationally
In southeastern Michigan, near Detroit, in 2002 little green aliens landed and have been wreaking havoc ever since. The aliens are not extraterrestrial aliens, but invasive insects from the Orient brought over by accident and they are causing significant destruction to ash trees across the country. “Emerald Ash Borer (EAB) is an exotic wood boring pest from China and the Orient. In 2002, in Detroit, there was a problem with the ash trees, they were dying quickly and it was thought to be a disease called ash yellow”, explained Robin Usborne, Communications Manager with the Michigan State University Department of Entomology and the Emerald Ash Borer Information Network.
The initial identification of the emerald ash borer was no easy task. Entomologists had never seen the species and were initially baffled. “One nursery owner brought in larvae to an extension office from one of his trees. They were unable to identify it and took it to Michigan State University to the entomology diagnostics group, they were pretty sure they had an Agrilus, but they didn’t know what the species was, so they sent it on to the USDA Forest Service. It finally went to the sonian, and when they couldn’t find it there, they were sure they had an invasive species. Eventually, they found a group of entomologists specializing in wood boring insects in Bratislava who identified it as emerald ash borer or Agrilus planipennis”, stated Ms. Usborne. “From there the entomologists wanted to know where it came from and how to control it. Unfortunately, they couldn’t find any information on it in any of the Chinese journals they had except for one piece of research that was two pages long from an entomologist in China, who after he was contacted said, “what you see is all I have, everything else I knew and studied about the emerald ash borer was destroyed in the Chinese revolution.” Entomologists have been working from that point forward to learn what it is, what its lifecycle is, and how to control it, basically starting from square one.”
Once entomologists knew what they were dealing with, quarantine areas were set up around the Detroit area in hopes of controlling the spread of the EAB. However, as people began bringing in information on ash trees that were sick, they had to extend the quarantine areas. The emerald ash borer has spread significantly since its introduction in 2002 being identified in 29 states and 2 Canadian provinces.
“Movement of firewood has been shown to be a big reason why emerald ash borer has spread”, explained Ms. Usborne. “It’s a hard bug to see, it’s not like one of these big bugs, they are little and green. The adults are usually up in the canopy, so you usually don’t see them. They lay their eggs in the canopy and once they lay their eggs, the larvae bore into the wood. It’s one of those things where you may not know your tree is infested for a couple of years or until your trees start dying.”
In order to prevent the spread of the emerald ash borer, several states are developing plans to educate the public and monitor for the pests, especially for adventurers and campers. In the northwestern United States, where the emerald ash borer has not yet been identified, land managers remain vigilant and do everything they can to prevent the introduction of this destructive pest. The Washington Invasive Species Council was established by the state legislature in 2006 and tasked with providing policy level direction, planning and coordination for combating harmful invasive species throughout Washington and preventing the introduction of new harmful species.
“In Washington, we participate in the "Don’t Move Firewood", or "Buy It Where You Burn It Campaign”, said Justin Bush, executive coordinator for the Washington Invasive Species Council. “We adopted the campaign that was a national campaign started by the Nature Conservancy that addresses the pathway of moving insects through firewood by moving firewood from one location to another. Over a number of years, we’ve seen the transport of firewood being the pathway to transport invasive insects such as the emerald ash borer or the Asian longhorn beetle, and this can easily be avoided through some really easy behavior changes. What we are asking people to do, is to simply buy their firewood at the location where they will burn it.”
With people being more mobile now than ever and with the increasing popularity of RVing, land managers are focusing much of their efforts on educating the public in an attempt to prevent the spread of destructive pests. What makes species like the emerald ash borer so hard to identify is that they are not on the surface of the wood you might pick up for your campfire, but they have bored into the wood and cannot be easily seen. “Many of the species actually have larval stages where the larva is located inside of the wood, so if you fall a tree for firewood, the larva can be inside the tree at the time and survive the process of being dried. Often times, we are seeing months later, adult insects burrowing their way out of the firewood and going on about their lifecycle as adults outside of the wood, so if you move the infected firewood from one state to another, you could be moving these insects”, stated Mr. Bush. “It’s not only an invasive species issue, you could be moving native disease from one location to another, or native insects from one part of the country to another. It’s [the Buy It Where You Burn It program] a great way to prevent forest diseases and improve forest health.”
While the emerald ash borer hasn’t been established in Washington yet, land managers have plenty of experience dealing with invasive pests. “We focus on those species that have been established in our forest ecosystems. They came in and became established, and became a part of the ecosystem. They are so widespread at this point, that we can’t get rid of them so as the Department of Natural Resources in the forest, we manage for those species like we would with other native forest pests”, explains Glenn Kohler forest entomologist with the Washington Department of Natural Resources. “One good example is the balsam wooly adelgid, it’s from Europe and was introduced to the northwest in the 1930’s. It’s a sucking insect like an aphid, but only on conifers. It damages the true firs like the grand fir and the sub-alpine fir and can cause mortality.”
Options for controlling invasive species once they are established are few and far between. Generally speaking, the native species do not have defenses to protect against the alien invaders and they can take a heavy toll. Land managers attempt various methods of control including, chemical control, introducing predators for the invasive species or biological control, or breeding programs to build resistant strains of trees. “With invasive species like blister rust, there are breeding programs going on to create seed plants that might be more resistant. It’s very challenging, the program has been going on for several decades and DNR has been assisting with planting the seedlings they have created and testing them in the field. They have some families of trees that are showing some level of tolerance to the disease, they still get the disease, but they can live through it. It’s a long-term process, it’s not like breeding tomatoes where you can get some new seeds in a few months”, said Mr. Kohler.
The potential destructive force from invasive species varies, but introducing any new species is not a risk that land managers are willing to take. “Some of the insects, for example the rusty tussock moth that’s from Europe, doesn’t really seem to do any damage. There are lots of examples of things like that. They are here and reproducing, but they are not causing an impact on forest management. But there are some that are on the horizon like the emerald ash borer or the gypsy moth, that could potentially cause heavy damage”, said Mr. Kohler.
While some like the rusty tussock moth don’t seem to have an impact, others like the emerald ash borer have caused millions of dollars in damage across the country. “The reason it [emerald ash borer] has been labeled by the forest entomologists that have worked on it as the most destructive invasive wood boring insect they have ever seen, is because it takes no prisoners with ash trees. It doesn’t care what species it is, how healthy it is, it will attack them all, and ash trees have no defenses because they have never seen them before. That’s why we see such a huge destruction of ash tree”, explained Ms. Usborne.
“In Washington, we don’t have emerald ash borer yet. Emerald ash borer has been moving westward and to the south over the last two decades. Any firewood could potentially be moving the emerald ash borer to the Pacific Northwest, and the emerald ash borer can attack any Fraxinus species, ash species, and in Washington, ash is a big portion of our urban forest. It is also a component of our natural forest, our native ash is typically located in southern Washington”, Bush said.
“I’d like to reiterate how important it is for the public to be aware of these things and their potential role in moving them around. If they are moving wood or live plants over long distances across state lines, they should think twice about it”, said Mr. Kohler.
Jared Langenegger
A graduate of New Mexico State University with B.S. in wildlife and fisheries science, Jared spent 15 years working in fisheries and parks management. He enjoys camping, fishing, hunting, painting, and wood working.
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