Tuesday 7 March 2017

Ancient hieroglyphics, or???

If you are out and happen to see these patterns on a barkless tree trunk, you might wonder just what has created this.

It isn't some form of ancient writing, of course, but the markings of a non-native and highly invasive insect known as the Emerald Ash Borer (EAB).

The EAB is a metallic green beetle that is native to Asia. The consensus is that it arrived in North America via wood packing material, which isn't surprising in many ways due to the huge volume of things that North America purchases from Asian countries. It was first detected in Michigan in the late 1990s, and shortly afterwards, expanded into southern Ontario, being first detected there at Windsor.

The EAB specializes in feasting on ash (Fraxinus spp) trees. In its homeland, it is not considered a major problem since the ash species there apparently have built-in resistance. However North American ash trees do not have that resistance, and so are quite vulnerable. The adult EAB feeds on the leaves and are not all that destructive, but the larvae burrow under the bark, feeding on the woody material immediately under the bark. This is where the critical transfer of sap and nutrients to feed the tree takes place, and the larvae's burrowing and feeding action cuts off the flow. In fairly short order the upper part of the tree dies. The roots may still be alive and there may be some subsequent sucker growth of the tree, but it will likely never grow to a mature specimen.

The EAB has quickly spread in less than two decades to many provinces and states around the Great Lakes and points farther east. The travel of adults to colonize new areas is facilitated by wind, so the prevailing westerly and southwesterly winds cause eastward spread more quickly than westward spread.

Ash trees are a major component of eastern deciduous forests. Or at least they used to be. There are several species of ash occurring in southern Ontario: White Ash, Red Ash (and its varietal form, Green Ash), Black Ash, Blue Ash and the only 'non-colourful' one, Pumpkin Ash. All species are susceptible to the EAB, although it has been surmised that Blue Ash is somewhat more resistant.

Due to the aggressive nature of the EAB most forests in southern Ontario, and especially southwestern Ontario, have been devastated, and dead ash trees are now dominant. But given the brittle nature of standing dead ash trees, many are now snapping off and if they don't get hung up in an adjacent tree, come crashing to the ground. Every moderate to severe wind storm brings more and more down.

The main reason for the preceding discussion is that over the past few weeks I have had quite a few comments and questions directed my way regarding the apparent unsightly mess along the roads and trails of Rondeau Provincial Park. The mess is actually the result of the attention being given to the thousands of dead ash trees.

So many falling trees are a hazard, to people, to vehicles and to the structures in the forest. This next image shows a couple of trees that came down and not only blocked the trail, but also did some major damage to the information sign along the trail.
 This next image shows a repaired boardwalk structure along the Tuliptree Trail, which was heavily damaged when a dead ash tree fell on it.

There is currently a major effort to take down the myriad dead ash trees along the roads and trails, in a controlled manor rather than waiting for the next few wind storms. As a result, the road sides and trails look a bit unsightly, to be sure.

This next image shows one of my favourite views along the Tuliptree Trail, taken in April, 2014.
Now it looks like this next photo, so the nice clean appearance of the above photo will take a few years to get back to.

For anyone planning to visit Rondeau in the next few weeks, scenes like this will be commonplace, but please bear in mind that it is a temporary appearance. The dead ash trees will decompose fairly quickly in the next few years. The freshly cut stumps will gradually weather and blend into the background, and with the growing season beginning in May, the greenery will cover up the messy look to some extent.

Major changes to the forest are a periodic occurrence. In some forest ecosystems, fire occurs periodically, killing trees and shrubs that are not resistant to fire. In other forest ecosystems, major wind storms or ice storms cause significant changes. At Rondeau, I can remember several such events:
-a huge ice storm in March of 1976, where many trees or major limbs came crashing down and virtually every tree in the park was affected;
-major winter blizzards with high winds occurred in late January of 1977 and 1978, causing major damage;
-more recently was the major downdraft of July 1998 that caused considerable damage to many trees (and structures).

Admittedly the outbreak of the EAB is not as natural an event as a storm, but the results are much the same. And just as the forest recovered to varying degrees following those other major events, I expect that the forest will recover after the ash trees cease to become a dominant species. But it will never be quite the same.


  1. I have seen a lot of those hieroglyphics lately! Many dead ash trees have been blown down in the last couple of month. Hopefully some of those uncommon Blue Ash will survive.

    1. Yes....the devastation of the ash trees at Rondeau are just an example of the devastation anywhere in SW Ontario where ash occurs. Undoubtedly some Blue Ash will survive, but may not make it to maturity and seed production. Time will tell.

  2. Not many of the nasty bugs up here yet, but worried about the devastation to come!

    1. Enjoy the ash while you can, unless something comes along in the meantime to minimize the EAB.

  3. Yep it's a nasty bug. I live north of Toronto and last spring we had to have the 30+ foot ash tree on our front lawn cut down as EAB had practically destroyed it. Most of the ash trees on our street have either been cut down or are dying from it.

    1. Its devastation is a little patchy, possibly due to the EAB being inadvertently transported to areas beyond their normal expansion, resulting in a new hot spot from which the beast will infest and move on from. I was at Guelph a few days ago, and many of the ash there seem not to have been affected....yet.