In August of 2024, four trees in the Killarney and Yellowhead Corridor East neighbourhoods in the City Edmonton, were identified to be infected with Dutch elm disease (DED). Although it is not possible to determine how the disease arrived in Edmonton, DED is often brought to new regions through the transport of firewood or by importing infected elm trees. Three of the elm trees were city-owned, and one privately owned.
Sarah McPike, Biological Sciences Technician with the City of Edmonton and a Director of the Society to Prevent Dutch Elm Disease (STOPDED) spotted the initial suspect DED infected tree while driving through the neighborhood. This tree was completely dead tree with a 55 cm DBH. Sarah observed the tree had peeling bark, with galleries, and numerous larvae and adults of banded elm bark beetle present.
Samples from this tree were submitted to the Alberta Plant Health Lab (APHL) also located in Edmonton. Since the tree sample was dry and dead no cultures were able to be recovered. Technically, the tree sample came back from the lab as negative for DED, but was strongly suspected that it actually died of DED infection. This tree is not included in the number of the 4 positive trees in Edmonton.
The initial tree looked like it was on private property, on the front lawn of an apartment complex, but curb to property measures showed it was actually on City of Edmonton property. It was not included in the city inventory, had not been maintained by city crews, and did not appear to have been maintained recently by the property owner.
After an intense surveillance in the area 3 city owned trees along 127 Ave were sampled and tested positive. They ranged from 15 and 25 cm DBH. Two of them were about 150 m from the initial tree, equidistant east and west from that tree. The third was about 100 m further west.
The fourth positive tree was found on private property 500 m to the northwest of the western-most positive tree on 128 Ave, and was about 35 cm DBH. A notice was sent to the property owner to remove and dispose of the infected tree. Removal was supervised by the City of Edmonton and CFIA staff.
The initial tree, as well as all the trees that tested positive for DED have been removed and disposed off as per the Provincial DED Prevention and Control Measures. Any elms within 20 meters of these elms were also removed as a precaution against the disease having spread by root graft.
Surveillance and monitoring were intensified in the region of the positive trees. There are approximately 50 or 60 city elm trees (all 15 - 25 cm DBH) between the positive trees. There are a total of approximately 175 elms on that 127 Ave boulevard. 30+ additional trees with wilt symptoms were submitted to the APHL and all came back negative. Trees with even minor symptoms have been placed on a watch list for continued surveillance. Several trees with high levels of decline have been removed, even though they did not test positive.
All of the city elms on 127 Ave have been injected with TreeAzin to help combat European elm scale, which all of those trees had present.
It is important to note that all suspect DED elm trees, both public and private are the responsibility of the municipality to sample. Under the Alberta Agricultural Pests Act (APA) “Pest and Nuisance Control Regulation (PNCR)” the DED pathogen is a named declared pest. All municipalities, counties and MDs in the province of Alberta have the responsibility and authority to prevent and control DED under the APA. The APHL accepts samples only from municipalities, counties, MD’s ad Special Areas, not from the home owner or private pruning companies.
https://open.alberta.ca/publications/dutch-elm-disease-prevention-control-measures-responsibilities-authority-apa
Since all Provincial and Federal DED requirements have been followed Alberta is still considered DED free at this point. The City of Edmonton will be doing extensive surveillance for DED and monitoring for the elm bark beetles in the following years.