The Pacific Northwest has many native species of flora and fauna, but this region is also home to invasive plants and animals, such as Himalayan blackberries and bullfrogs. Invasive species typically adapt quickly within a new environment and successfully reproduce, disrupting the existing ecosystem and often causing significant damage.
One such invasive species that hasn’t yet reached the Pacific Northwest is the Emerald Ash Borer, or Agrilus planipennis. This beetle is a wood-boring pest of ash trees that are native to Asia, but has also established itself within the U.S., causing widespread destruction to tens of millions of ash trees.
Here are some important things you need to know about this species, and how to prepare
The Emerald Ash Borer was first detected in southeastern Michigan in the summer of 2002; before June of that year, the beetle had never been found in North America. The following year, it was confirmed in Ohio and Maryland, and by 2007, it had spread to Illinois, Indiana, Ohio, Pennsylvania, and West Virginia.
Nearly every year since, new states have confirmed the presence of the Emerald Ash Borer, with the beetle currently found in 30 states. From Michigan, it has moved westward and can be found as far as Colorado. Currently, Oregon and Washington do not have any confirmed reports, but both states have identified this invasive species as a top priority to monitor and prevent from establishing itself in our ecosystems.
The Emerald Ash Borer most likely arrived in the U.S. from Asia through the transport of wood packing materials and has continued to spread domestically through the movement of infested timber, firewood, and nursery stock.
Any wood product made from ash trees is highly susceptible, including debris, chips, and trimmings. What makes it even trickier is that all of these materials can spread the infestation, even if no beetles are visible.
In North America, the Emerald Ash Borer is known to infest all species of ash tree and has thus far killed millions of trees in regions where it has adapted to the native environment. Depending on how healthy a tree is, it can take only a few years for an infestation of emerald ash borers to kill an ash tree.
Adults eat the leaves and lay eggs between the layers of bark. Within a week, the larvae will hatch and then cause the bulk of the damage by burrowing further underneath the bark and eating away at the layers of tissue that are critical to transporting water and nutrients throughout the tree.
Without these resources, the tree gradually dies and a large-scale infestation can have a massive impact on local economies by destroying valuable trees for timber production.
It also results in the loss of ash from city and suburban landscapes.
The Emerald Ash Borer is considered one of the costliest forest invasive species to have ever existed in North America, and possibly the most destructive alien plant species in North American forests to date.
To make matters worse, ash trees have no natural defense against this threat, meaning that the Emerald Ash Borer will kill nearly every single tree it encounters.
The Emerald Ash Borer poses a significant threat to the Pacific Northwest, including the Portland-Vancouver metro area. Wild native Oregon ash (Fraxiunus latifolia) is found in both Oregon and Southwestern Washington, and other species such as white ash and green ash are often used for landscaping and as ornamental shade trees in parks and along streets in cities and towns throughout the region.
We know that the beetle is commonly introduced to a new area by the movement of firewood, and many states with confirmed Emerald Ash Borer infestations have put a quarantine on transporting firewood in order to prevent further spread.
However, a general lack of awareness about of these risks means that unintentional relocation is still a very real possibility, and homeowners in the Pacific Northwest should be on high alert for signs that the Emerald Ash Borer has taken up residence in local ash trees.
The Emerald Ash Borer is a small beetle that is about a third of an inch to half an inch long, with a narrow body, and a flattened head. Its wings are green and iridescent, and when the beetle lifts its wings, its copper, reddish, or slightly purple abdomen can be seen.
Adults are usually active during the summer months after they emerge in May from the trees where they hatched as larvae. During this process, the adult beetle must chew its way out of the tree where it creates distinct D-shaped exit holes. These holes are a sign of a potential infestation and are one indicator to look for if you have ash trees on your property.
Other signs could include an increase in woodpecker damage on ash trees, as woodpeckers eat Emerald Ash Borer larvae and the thinning of the leaf canopy in the upper part of the tree due to damaged bark and tissue.
Flagging limbs, dead branches, and vertical bark splits are also indicators of an infestation.
Property owners who notice any of these signs when examining their ash trees should report the information to local agencies right away, and consult with a Vancouver arborist as to how the infestation can be managed to prevent further spread.
While the Emerald Ash Borer has not reached the Pacific Northwest yet, it is highly possible that it may do so in the future, especially with our numerous recreation opportunities and campgrounds that attract out-of-state visitors with potentially infested firewood.
State agencies are already on heightened alert and monitoring any potential appearance of this invader so as to prevent widespread damage and loss that has already occurred in other parts of the country. Experienced Portland and Vancouver arborists are also ready to come to the aid of ash trees with treatment options that can prevent infestation in the first place.
Since the presence of the beetle is often difficult to initially detect, consulting with a Vancouver arborist is an important step toward protecting any healthy existing ash tree populations. Arborists with the right knowledge will be able to recognize the early signs of the Emerald Ash Borer, and can then design a management plan for dealing with the issue and preventing any further damage.
It’s important to work with an arborist who can answer your questions, provide the right information, and help you make decisions regarding potential or existing damage to trees. With awareness and action, the ash trees of the Pacific Northwest may be able to withstand the threat posed by the Emerald Ash Borer and continue to be an area where trees thrive for many years.