The largest elm tree in Seattle once sat in the Wallingford area, but in 2013 it was removed through a process that required tree climbers and a crane. The reasoning for the removal: Dutch Elm Disease, a disease that can be prevented if the tree is properly treated.
“I would say it’s almost inevitable that elms in the city area will be attacked if they’re not treated,” Tree Solutions Inc. principal and founder Scott Baker said.
Elm trees like the one that resided in Wallingford can be found on SPU’s campus and must be treated every three years to avoid the fatal consequence that the elm in Wallingford encountered.
American elm trees surround Tiffany Loop and the bus stop area between West Nickerson and West Bertona Street. All 20 elm trees require a fungicide injection process to prevent them from getting DED.
Baker stresses the importance of treating the trees because treatment can prevent elms from dying from the disease.
SPU master gardener Jeff Daley says the elm trees were planted around 1891, when the university first opened.
For Daley, they are an important element on campus.
“These trees speak volumes of our campus,” Daley said. “They are the welcome mat welcoming people in … not many universities have a beautiful park-like setting like this.”
In regards to the structural health of the elm trees, Daley noted the impact that location has on them.
“Because we’re located on the north side of Queen Anne Hill, most of our big, strong winds come from the southwest, so Queen Anne Hill blocks the wind and protects the trees … and that’s why structurally they’re in as good of shape as they are,” Daley said.
According to the City of Seattle Dutch Elm Disease Elm Tree Protection Program, the disease was likely first spread by travelers who transported diseased firewood.
It’s caused by the Ophiostoma ulmi fungus which is transmitted by elm bark beetles who serve as a vector for the disease.
If the beetles have been in infected wood, they carry fungal spores of the disease when they bore into the bark of a healthy tree, then spreading it into the tree and causing infection.
Baker explained that the disease moves through the vascular system of the tree (the sap) and blocks the vessels of the tree that deliver nutrients from the leaves. The blockage causes the leaves to wilt and no longer function, and eventually the tree dies.
“The beetle can’t fly very far, so if you had an elm that was very remote, then it may never get attacked,” Baker said. It has to be near an elm that has the disease that’s had a beetle in it, and the beetle has to fly to another tree to move the disease.”
To prevent the American elm trees on campus from getting DED, Tree Solutions Inc. associate consultant Haley Galbraith began the injection process last Tuesday morning, May 3. It’s a process that is done at SPU every three years.
According to Baker, it’s important to treat the trees every three years.
“The residual chemical works in the tree for three years, so at the end of that period if the tree is infected it won’t be protected … the success rate is about 99 percent, so it’s very, very effective, but only if you continue to do it,” Baker said.
To treat the trees, Galbraith uses a “Wedgle Direct-Inject System” to insert a fungicide into each point of injection on the tree.
“Between the bark plates, where you see kind of a lighter, sometimes it’s reddish-orange, new growth pushing through, that’s the primo spot to place your injection site.” Galbraith said. “You don’t want to put it in crevasses [or] between structural roots.”
The injection system minimizes harm to the tree in contrast to a macro-infusion method which is more invasive as it requires holes to be drilled into the tree and the fungicide to be injected by a pump.
“It’s all contained, there’s no mixing or dilution of the chemical,” Galbraith said about the direct-inject system. “It’s just in this little bottle, so I just pop it right on, and there’s a needle that I put on. Once all this material has been pumped through, this outer layer is recyclable and the inner bank can be disposed of.”
For each tree, Galbraith determines the amount of injection sites and distributes the fungicide into each site.
“The number of injection sites depends on the size of the tree, and the general recommendation is every four inches around the base, as low on the base as you can get them,” Galbraith said.
While this is the recommendation, Galbraith explained that it depends on the structure of the tree.
According to Galbraith, the recommended amount of fungicide to be injected ranges from five milliliters, as a low dose, to 10 milliliters, as a high dose.
“I’m doing a moderate to high dose, just because there is a moderate level of infestation pressure in our area,” Galbraith said.
In addition to the elm bark beetle, Baker explained that the disease can be spread from tree to tree through roots that are touching each other.
“We have no method of getting the fungicide into the roots of the trees, so we’re only protecting the upper parts of the tree, and that’s been a big issue because [in] places in Seattle, there are several neighborhoods … that have extensive plantings of elm … so if one person treats their tree and the next person down the block doesn’t … [it] can be killed as well if the roots are touching,” Baker said.
According to Baker, the reasons elms are still alive is because the bark beetle can’t fly very far and that tree care companies have invested money in research on how to protect the trees from getting DED.
Baker said he hopes to teach the university more about trees and the importance of treating the elm trees because he feels it’s something people should be more aware of.
“People are always curious when they see us out there poking and prodding around the trees…we get a lot of questions, and I just think it’s a great campus … a campus like that has a great opportunity to send alumni away with a better understanding of trees and why they’re important,” Baker said.