Dutch Elm Disease

Dutch Elm Disease (D.E.D) Ophiostoma novo-ulmi is a fungus that effects Elm’s Ulmus spp or Zelkova which is native to Europe. American Elm is the most susceptible. This fungus grows inside the xylem of the plant, this inhibits the trees ability to move water through the tree. This kills large parts of the tree, and causes wilting. This can spread quickly between Elm trees that have root grafts between there root systems.

In the spring infected trees will have few to no leaves on some branches. In early summer green leaves will wilt or droop on branches. Some leaves may even turn brown, but the leaves will not fall off they will cling to the tree. In late summer leaves will turn yellow and droop these leaves this is a common occurrence known as flagging. These leaves are also known to fall off of the tree prematurely. Branches on the truck will wilt and turn brown as well. 

What can you do to keep D.E.D out of Alberta? Make the effort to keep our trees healthy, this can be as simple as watering from April to mid-August. Watering your trees very well before the ground freezes for the winter can also help the trees to harden off. Dead and dying branches are the perfect place for the Bark Beetle to make its home. These should be taken care of and disposed of properly by either burning or burying the wood. 

These are some things you should not do. Do not store elm firewood, it is illegal and can be a breeding area or the beetle. Do not transport firewood into or even within Alberta. There is a pruning ban effective between April 1st and September 30th each year. Do not prune elm trees within this time frame.

Emerald Ash Borer

Emerald Ash Borer Agrilus planipennis is not common to Alberta, Canada or the United States. It is an invasive species from Asia that were first introduced in the United States in the mid 1900’s, has now been found in southern Ontario. This beautiful beetle is <10.0–13.0 mm in length. With a coppery abdomen, the elytra can be a duller green, purple, blue or even copper in color.

The larva eat the soft wood underneath of the bark, hindering the tree from moving water or sugars throughout the tree. This can kill a tree in one to three years.

This insect prefers Green Ash fraxinus pennsylvanica over Black Ash Fraxinus nigra, but it has been found on both these species in the USA and Ontario. Green Ash make up a large part of the street tree canopy of Calgary. The Emerald Ash Borer knows no boundaries and is headed our way. It is no longer a question of if, but of when.

So what can you do to prevent too spread of Emerald Ash Borer? Don’t bring fire wood across our Alberta border, prune the dead branches out of your trees, water and fertilize applications. Removing the low value trees from our landscape can help us to center our preventative measures on higher value trees.

There is a biological insecticide being used in Ontario called TreeAzin. This is a systemic pesticide that is injected into the tree, this should be applied every two years. This can be used on already infected trees. This has been tested throughout the USA and Canada for control of Emerald Ash Borer and has proved to be successful.