March 1, 2019
Dutch elm disease is a huge problem in Western Canada, afflicting trees from Nova Scotia to Alberta. It is a highly contagious fungal disease with a high mortality rate, nearly always killing affected trees.
It is best treated proactively, protecting trees before they are infected. And treatment is most effective during winter months, before April, so it’s important to act now. Here’s everything you need to know about how to prevent and protect your trees from this deadly contagion.
What is Dutch Elm Disease?
Because it is a fungus that can live in imported timber, Dutch elm disease was first introduced to Europe and America through timber shipments from the far east. While early attempts at quarantining the disease in New York and New England were largely effective, many of these quarantines and controls were relaxed during WWII, when the disease first reached Canadian trees and began to spread westward.
Alberta has been relatively lucky, in that there hasn’t been a major outbreak of DED. However, according to Alberta Agriculture and Forestry, there was one tree confirmed to have the disease in Wainwright. It was immediately destroyed.
Dutch elm disease is caused by a fungus that originated in Asia. However, it was first identified and classified in the Netherlands, hence the name “Dutch Elm Disease”. It is actually caused by three distinct fungi and spread from tree to tree by three different species of elm beetle.
Female elm beetles burrow into elm trees, creating a space between the bark and the trunk in which to lay eggs. They prefer dead or weakened wood and are attracted to trees already afflicted with the fungus. The fungus thrives in the spaces created by the beetle, and, when the young beetles leave their host tree to feed on healthy trees, they carry the fungus on their bodies. The disease can also spread through root grafts and root-to-root contact, as uninfected roots are exposed to the fungus.
For this reason, many early treatments for Dutch elm disease used insecticides to kill the beetles, but such treatments had unwanted environmental consequences, and are seldom used today.
Signs of Dutch Elm Disease
Because the disease is so virulent, by the time signs of infection are spotted, it may be too late to save the tree. However, it is crucial to be alert to identifying the signs of Dutch elm disease, because even if the tree can’t be saved, the disease should be contained as early as possible to prevent it from infecting other trees.
DED attacks the vascular system of the tree, starting with small branches near the top of the crown. As the tree defends itself, it blocks its own vascular system, eventually killing off leaves, stems, and branches. Deprived of nutrients, the roots then die as well. A healthy, vigorous tree may live for up to a year after being infected, but unfortunately, that year simply creates more time for the fungus to grow and spread.
To identify Dutch elm disease, look for wilting and yellowing leaves high in the crown of the tree, well out of autumnal season. Leaves will wilt, yellow, and drop, and then the wilting will progress to nearby branches. Root infections will be visible in early spring, as new leaf growth will be weak, pale, and stressed, and die quickly. Dutch elm disease also often creates a distinctive scar on the bark, which can be visible in infected trees.
If a tree is infected, it is crucial that it be treated, quarantined, or destroyed before April, when the next generation of beetles emerges and spreads the fungus to nearby trees.
How to Protect Your Elm Trees
There are several ways to protect your trees and prevent the spread of this disease
1. Take expert care of your existing elm trees.
Healthy, vigorous trees are less attractive to bark beetles, and therefore a reduced vector for the fungus. To care for your elm trees and prevent the spread of infection:
Water elm trees regularly from April through mid-August. Then stop regular watering, with only one or two deep waterings before winter freezes.
Prune elm trees to remove any weak or unhealthy branches that may be beetle habitat. Pruning should be done in winter months, and all elm wood must be disposed of immediately and properly.
To prevent the spread of the disease, experts recommend that you do not:
- Allow pruned or trimmed branches to remain untended
- Store elm wood for use as firewood
- Chip elm wood any larger than 2.5 cm
- Transport elm wood logs, firewood, or other elm material to another location
2. Report any possible sightings of Dutch elm disease.
There are Dutch elm disease hotlines throughout Canada. Contact the Society To Prevent Dutch Elm Disease (STOPDED).
3. Prevent infection of Dutch elm disease.
There are a number of methods that can help to prevent infection with Dutch elm disease. There are, essentially, “vaccines” that can prevent infection, but most must be repeated annually. Proactive measures are the best way to protect high-value elm trees. In fact, the Alberta Government has the estimated value of these elm trees at $2billion.
4. Treat afflicted trees early.
There are a variety of different methods that can be used to try to save infected trees. But, trees must be treated as early as possible before spring beetle activity spreads the disease.
Dutch elm disease is a threat to our urban and rural forested areas. This threat to our elm trees also has negative consequences for a host of other species that rely on healthy trees and healthy forests for survival.
How Pevach Can Help Fight Dutch Elm Disease
At Pevach Corp., we are not only experts on tree care and removal, but we are passionate about protecting the health and beauty of our communities.
We can help prevent Dutch elm disease at every step, by providing expert care and maintenance of healthy trees, disease prevention in at-risk trees, and disposal of infected trees. Our experienced staff and powerful tools will help manage your elm trees, and we can manage even the toughest jobs on the roughest terrain.
Together we can protect valuable urban landscapes and the natural environment of Alberta and Saskatchewan, but time is of the essence because Dutch elm can only be treated between October and the end of March. Contact us for a quote in 24 hours or less.
