Sheridan’s trees have been invaded and we need to fight back!
The sad truth is that some trees around the Davis Campus are dying and have become a hazard to faculty, staff and students. Facilities Services will begin a first round of removals during the upcoming reading week break, taking down approximately 35 trees that pose a risk to the Davis Campus’ highest traffic outdoor areas. Further removal will continue in phases later this year. In total, about 120 trees have been affected by various factors, described in more detail below.
There are a variety of species that surround the grounds. The main groups in trouble consist of the Ash tree, Jack Pine, Pin Oaks, Elms and new young Maples, but there are many species still alive and thriving. And although every one of these species is aesthetically beautiful to see around campus, they have been hit with a wide range of problems.
Some of them have died due to poor soil conditions, heat/drought stress, old age, or poor species selection for the site (often a combination of factors over a singular). However, the largest proportion (about 100 of the 120 mentioned above) have died due to pest infestation, specifically the Ash Tree has been hit the hardest by one of its greatest enemies, the fearsome Emerald Ash Borer.
A former infested Ash tree at the Trafalgar campus that had snapped close to the base. This tree was removed.
Native to Asia, it came as a shock to see signs of EAB damage as the reason for Ash populations diminishing in Ontario. Before the turn of the century, Ash was the perfect species to place at the Davis Campus because of its ability to thrive in urban settings. In fact, its durability was a key factor in why the Ash was chosen as one of the dominating trees for the Davis canopy. Today, with over 100 Ash trees in poor health surrounding the grounds, something has to be done.
The EAB is believed to have established itself in Ontario by way of Detroit, Michigan of the United States. They arrived in wood packaging pallets from Asia and crossed over to Canada, through Windsor, Ontario when dead Ash was sold as firewood in Canada.
The bright green pest may only grow to be 8.5-13.5 mm long, but the damage it causes in its larvae state is catastrophic. The female will lay about 60-90 eggs in the crevices of the bark. Once hatched, the larvae (26-33mm long) bore their way through the bark using pincers, until they arrive at what is called the Vascular Cambium, the layer of the tree that acts as a sort of life giving highway. The roots collect water and nutrients for the leaves and the leaves produce sugars for the whole tree with the Vascular Cambium acting as the delivery route to all sections of the tree.
The ash borer beetle and larvae.
The EAB begin to tunnel in an S shape in late summer/early fall until the winter where they rest in their pupae or cocoon like state. In the spring, they tunnel their way out leaving a ‘D’ shaped hole when exiting through the bark and fly away to live their one-year life cycle. Only to repeat this process, come autumn.
Some signs of EAB damage vary from lime coloured foliage, smaller leaves, flaking bark, cracking in the trunk and branches, and epicormics shoots (sucker-like growth off of the trunk or mature sections of branches). But girdled branches and trunks are one of the most obvious to spot. Girdling is when EAB damage encircles a branch/trunk restricting the travelling water/nutrients. Rings of decayed bark then fall off dead areas of the tree exposing inner layers of absolute carnage and the resulting section of canopy dies. EAB usually kill Ash in about 2-3 years. They then become major safety hazards for everyone at the college.
The loss of moisture content compromises the overall strength of the tree causing it to break under static or dynamic loading.
An example of static loading can be seen in winter, if an infested Ash has too much snow or ice on top of it’s branches it will have a greater chance of breaking and falling near/on passersby. And the same applies for dynamic loading, which means varying amounts of force such as wind on a stormy day, which may cause sections of the brittle tree to fall as well.
At Sheridan we pride ourselves on having natural beauty surrounding our campuses. We believe that having a healthy and diverse landscape only improves the atmosphere and culture for students, staff and faculty.
Yes, we may be losing some of our amazing tree canopy in the short term, but we will find a way to restore and cultivate an even better, healthier environment for trees to thrive.
Sheridan College is saddened that these trees must come down, but we are grateful for the patience of students, staff and faculty while the removal process is taking place.
If you have any questions, please contact nathan.nettleton@sheridancollege.ca.