Article from Volume 6, Issue Number 1, 2019

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Tree Issues & Concerns 2019 – Winter 2019

By Carl Epp, Parkland Tree Care | Other articles by Carl Epp, Parkland Tree Care | Feature

TREE PEST: EMERALD ASH BORER

One of the two worst tragedies to affect our urban forest in Winnipeg is the discovery of Dutch Elm Disease (DED) in the mid 1970’s and now the discovery of Emerald Ash Borer (EAB) in the fall of 2017. 40 years after the discovery of DED we still have a large population of American Elm trees due to management that has slowed its spread. However, with EAB the prognosis even 10 years from now is that we will have no Ash trees surviving in Winnipeg except Ash trees that have been treated continuously over the coming years. All Ash tree species we have in Manitoba are susceptible to EAB.

Based on the experience of cities in Ontario, Quebec and much of the Eastern USA the current state of EAB in Winnipeg is currently at low levels but the population of the pest is slowly growing and spreading. At some point in the next few years ash trees will suddenly start to die. When that happens the rate of decline will be rapid and the time to treat against EAB will be past. At that point it will be time to remove these infected ash trees as quickly as possible.

It is important for all properties to inspect their Ash tree populations to determine which Ash trees they wish to keep (treat) and which trees are deemed not worthy of treating or are not worth the cost of treatment. The other issue to keep in mind when looking at Ash tree populations is that once these trees start to die from EAB they quickly become hazardous. EAB infected Ash trees experience unpredictable rates of trunk and branch failure which puts people and property at elevated levels of risk.

The take away as a result of EAB is to plan for the treatment or removal of your Ash trees before that choice is taken away from you by the EAB insect itself.

TREE PEST: COTTONY ASH PSYLLID

Another Ash insect that has moved into the Winnipeg area in the last several years is the Cotton Ash Psyllid (CAP). This tiny insect is similar to an aphid. It attacks Black and Manchurian Ash trees (not Green Ash) by sucking sap from the underside of leaves and at the same time injecting a toxin into the tree. This toxin kills the tree quite quickly (1-2 years). There is no effective treatment for this pest. As a result, whole streets planted with Black ash have died within the City of Winnipeg. This pest is found in Winnipeg and in many rural areas of Manitoba. When attacked the leaves of the Ash tree start to curl, shrivel and turn brown, there is a stage in midsummer when a white cottony like substance spreads across the underside of the leaves (Photo 1). Since there is no treatment the only solution is tree removal.

TREE PLANTING

In light of the above 2 pests it will be important to consider trees for replanting. Since Ash is such a hardy species it was overplanted over all the prairie provinces and so we find ourselves in this unfortunate place of loosing such a significant tree in our urban forest. It is important to not repeat this mistake by replanting too many of the same species, rather plant a large variety of tree types. There is a good pool of limited choices. It is important to remember that no tree is perfect under all circumstances and that every tree has some problems or issues that must be contended with.

When planting it is very important to look at the type of tree, its characteristics and habits and the planting site. Also, to be considered is planting density or spacing. I see examples every day where this was not considered when planting and now that the tree has out grown the space available there is a significant conflict (Photo 2). This must be addressed with tree removal or annual pruning maintenance to trim the tree back from the area of conflict. This is a problem especially on Condominium properties as it can involve many-many trees planted to the specifications of a landscape plan that didn’t consider the tree size at maturity. In some case the designer may have wanted to establish a landscape that quickly greened up and was very pleasing to the eye. The designer may or may not have anticipated the removal of a certain numbers of trees to thin the planting density once established. However, as you may already know it is very difficult to remove trees that have become over crowded on multi-unit condo properties without causing anger and resentment between unit owners and management boards. As a result, I recommend you plan your tree re-planting program by consulting a number of knowledgeable professionals including Arborists, Nurseries, and Landscape companies.

TREE PRUNING

The greatest gift you can give to a young tree is to start the pruning process early in its life. Early pruning with a view to the trees future growth helps to establish strong branching and strong trunks. PAGE 14 CCI MANITOBA CHAPTER TREE ISSUES & CONCERNS 2019 When planting it is very important to look at the type of tree, its characteristics and habits and the planting site.

The investment in pruning young and maturing trees will reduce the cost and frequency of the pruning cycle at maturity. It will also reduce the number of trees requiring removal at maturity due to defects that could have been addressed at early stages. These defects at maturity would never have seen the light of day at maturity had they been attended to early on.

When pruning is referenced, I am referring to the complete pruning of the crown from top to bottom by a knowledgeable arborist who can look at the tree and visualize issues that may arise in the future. Issues like co-dominance, included bark, narrow branch angle attachment, branch spacing, etc. Pruning that is only performed to address low hanging branches and branches in conflict with structures is not enough to care for the tree and ensure a long life.

The worst-case scenario is when a tree suffers a catastrophic branch or trunk failure due to a defect that could have been addressed early in its life through proper pruning (Photo 3). In my experience many properties where early pruning was not undertaken often suffer a higher incidence of storm damage.

In Summary the management of trees on properties is an investment in the future of the property and the well being of the people living there. Many studies in recent times have discovered huge benefits of trees in the urban forest to our own personal health and the environment. The bigger the tree the greater the benefit. Let’s take care of them!

CARL EPP is an ISA Certified Arborist with Parkland Tree Care Ltd.
Based in Winnipeg. Contact: info@parklandtreecare.ca