Since first appearing in North America in the 1990s, Emerald Ash Borer has been sweeping across the continent, decimating the ash tree population. Since it was first discovered in Canada in 2002 (near Windsor, Ontario), it has been spreading east and west throughout Canada and the United States. Emerald Ash Borer targets species of ash tree, one of the most prevalent trees on the continent.
While it spreads, scientists, researchers, and arborists have been continuing to develop ways to prevent its spread, treat infested trees, and find innovative ways to save our ash trees. The past few years have seen Emerald Ash Borer become a priority in many levels of government across North America, as states and provinces realize the depth of destruction this little beetle is taking with it.
In 2020, scientists and researchers made great strides in understanding more about the beetle, while EAB continued its westward and eastward journey. What did 2020 bring in our battle against this beetle?
What is the Emerald Ash Borer?
Emerald Ash Borer is a wood-boring beetle that is native to East Asia, and is found in China and Eastern Russia. Adults are narrowed bodied and metallic green (about the size of a dime’s diameter) with the ability to fly. While adult EAB can cause minor foliage damage, which can be detrimental to an ash tree with an already-severe infestation, it is the larvae that are of greatest concern.
Eggs are laid in crevices on the tree’s bark in mid-May to mid-August. They quickly hatch and the larvae burrow through to the inner bark. They then quietly and invisibly chew S-shaped tunnels under the bark that constrict the tree’s water and nutrient-conducting tissues.These tunnels can only be seen when the outer bark is removed, so it is very difficult for us to see an infestation until it’s too late and the tree has already started to die. The following May, these larvae emerge as adult beetles through D-shaped holes in the bark to lay their own eggs, and the cycle continues.
EAB larvae are so dangerous to a tree’s health that a heavily infested tree can die in as little as one year. Up to 99% of all ash trees are killed within 8-10 years once the beetle arrives in the area. First, the upper branches of a tree will start to thin and die, due to the inability of the tree to provide nutrients because of the tunnels. This thinning moves downwards until the entire tree has been killed.
Emerald Ash Borer has no North American natural predators currently, because it is an invasive species not native to our ecosystems.
Where has it been detected as of 2020?
As of the end of 2020, Emerald Ash Borer has been detected in five provinces and thirty five states.
Of particular note, it was detected in more regions in New Brunswick in this past year. In the United States, it was detected in more regions in western states, including South Dakota, Nebraska, Texas, and furthest west, Colorado. It was detected in more counties in the eastern United States as well, including those in Vermont, New York, Iowa, Kentucky, and North Carolina.
Many environmental and forestry professionals believe that New Mexico may be the next state that Emerald Ash Borer is detected and that without the proper precautions, Saskatchewan may detect it in the coming years.
To view detailed information about provinces, states, regions, and counties where Emerald Ash Borer has been detected in 2020, visit the Emerald Ash Borer info site.
Did 2020 bring more hope for treatment?
There have been a number of new developments in 2020 to find ways to help North America’s declining ash tree population.
The botanical insecticide TreeAzin® has been on the market for decades, and has proven an effective way to protect ash trees from Emerald Ash Borer. This insecticide is injected into the base of an ash tree in early summer and continues to work for two years on average. After two years, the tree will need to be injected again. This insecticide has proven effective in many cases for protecting ash trees from Emerald Ash Borer when injections are maintained.
In 2020, a group of scientists found candidate resistance genes that could protect ash trees from the Emerald Ash Borer. After sequencing the genomes from 22 species of ash trees, scientists were able to discern how the trees related to each other. They found that resistant species of ash trees killed EAB larvae when they burrowed into the bark, but susceptible ones did not. Their findings suggest that breeding or gene editing could be used to place these resistance genes into ash species currently affected by EAB in North America.
Research also continues into a biological control that infects the beetles with a naturally occurring fungus, which they spread to each other through mating. This is an alternative to using insecticide, and could prove an effective way for adult beetles to infect each other and drastically lower the amount of eggs laid each year.
Efforts also continued this year for the introduction of parasitic wasp species from EAB’s native East Asia to act as a natural predator that targets EAB specifically. These wasps have been introduced into the Canadian ecosystem for a number of years, as they specifically target Emerald Ash Borer and do not pose a threat to the rest of our ecosystem.
What can we expect in 2021?
The future in the battle against Emerald Ash Borer in North America may be a little brighter than it has been in years past. Research continues into finding natural ways to curb the effects of Emerald Ash Borer and create resistant ash trees.
There are regulated areas across Canada to control the movement of potentially infested materials. The United States also has dozens of regulation areas in thirty six states to prevent this movement. Ensure you’re following your local policies and don’t move firewood!
Unfortunately, if we aren’t able to follow directives and quarantines completely, we risk spreading Emerald Ash Borer further west, likely to Saskatchewan in Canada and New Mexico in the United States. In some parts of New Mexico, for example, local governments are pre-emptively planting more non-ash tree species to make up for any ash trees that may have to be removed in the future.
Emerald Ash Borer in Ontario
If you suspect that your ash tree may be infested with Emerald Ash Borer, P & A can perform an assessment to give you options moving forward. Anyone with ash trees on their property will be affected by Emerald Ash Borer at some point.
Contact P & A for more information.