Category: Tree Diseases

Fireblight is a tree disease that can affect many varieties of landscape trees and shrubs in your yard.  Correctly identifying this disease, and others, can be accurately diagnosed by your Best Edmonton Arborist.

Fireblight is a systemic, contagious bacterial tree disease that can destroy trees and shrubs that are in the Rosacea (Rose) family.  These include common specimens such as Apples, Crabapples, Mountain Ash, Hawthornes, Cotoneaster and Saskatoons in urban landscapes and commercial nurseries.    It is caused by the bacterial disease pathogen named Erwinia amylovora. 

The symptoms of this disease are quite typically easy to recognise, and usually can be identified on the newest fresh growth.  Spring flowers appear to be soggy and water-soaked, with new leaves wilted, appearing blackened along the veins. Branch tips start to hook over which is known as “flagging” or “shepherd’s crook”.  As the infection spreads and as the tissues further decline on the branches, the bark begins to appear sunken, water soaked and blackened.  Advanced infection develops into cracked, and entirely blackened branches, with the appearance of being “fire-scorched”.  Bacterial ooze may come from lesions on the bark, which can further spread infection.  This can be transmitted and spread by insects, birds, rain and wind distribution, as well as infected pruning tools. Plant tissue that has been damaged or injured, can also be susceptible to infection at these locations.

Fireblight Disease is spread most quickly during hot and wet weather.  It is mostly dormant during the coldest winter months, when the trees and bacteria are dormant.  The infection is carried from the point of infection through the tree’s vascular system and then systemically causes the demise of the tree.

Pruning, and removing to destroy all “infected” branches off your tree or shrub, with cleaned pruning tools, is crucial.  A sanitation solution of bleach and water, or bacteria-killing sanitizers, will be effective for cleaning your tools, between each pruning cut.   Always make sure that the diseased branches, and wood are disposed of correctly at the local landfill, and never use diseased mulch or wood chips in your landscape.

To aid in correct disease diagnosis and identification of the plants and trees in your yard, contact your Edmonton Arborist.

Dutch Elm Disease is a fungal disease that develops a fungus internally within Elm trees. The fungus grows rapidly within the trees eventually blocking off the tree’s vascular system.  This process stops the trees’ water conducting ability, causing the tree to wilt and then die.  The complete demise of a mature Elm, usually can happen within one or two growing seasons.

This devastating disease is mostly spread to other healthy Elm Trees, by 2 kinds of Elm Bark Beetles. (The Native Elm Bark Beetle, and the European Elm Bark Beetle).  These Beetles breed and lay eggs under the bark of dead, dying or cut Elm wood.  The new generation of beetles, emerge from dead and diseased wood, carrying the fungal spores with them on their bodies.  These beetles then move to healthy Elms to feed, spreading the fungal spores, thus spreading the disease. In urban environments with monocultures of Elm trees, growing close together, Dutch Elm Disease can spread underground, via grafted root systems.

If you have Elm tree pruning that is required or if you are concerned about your Elm tree health, contact an Arborist in Edmonton. To protect the Elm trees of Alberta it is essential to have your Elm tree pruning completed by your best Edmonton Arborist.

Black Knot Fungal Disease is the common name for the fungal tree organism Apiosporina morbosa, which causes a devastating tree disease in many places in Canada, including Alberta.  It is often found on commercial and private trees, as well as trees in the native, natural environment.  In Edmonton, several species of Cherry, and Plum trees are affected.  Most commonly, Mayday trees, Chokecherry Trees and Pin Cherry Trees.

Initially, a small swelling or green, olive-coloured gall will develop along branches of the tree.  These green swellings can grow up to 2-3 years before maturing into unsightly black growths. Once infected, the fungus grows internally, and will “girdle or choke -off” the tissue, causing the branch to decline , and potentially over time, resulting in branch death of complete tree loss.

The most obvious way to recognize Black Knot Fungal Disease are the visible black growths also known as “Knots”. These black “growths”, are usually spotted by an untrained eye, when the tree has lost all of it’s leaves.  These growths release fungal spores into the air. Spores spread more rapidly and further with the aid of wind, rain splash and insects or birds landing from branch to branch.

There are several ways to help control and/or slow the spread of Black Knot Fungal Disease.  The most direct way, when possible, is to prune for removal of the swellings well below this area during late Fall or Winter.  This will allow the knots to be clearly visible, as there will be no leaves on the tree.  As well, at this time the fungus will be less likely to spread, as the trees are dormant.  Secondly, cleaning or disinfecting of the pruning tools, followed by correct disposal of the removed, diseased branches, are crucial in control.  “Correct Disposal” consists of burning, burying or removal of infected tissue from location.  Note that even after pruning, these fungal spores can continue to disperse for several months.

A Certified Arborist is able to identify, and correctly put into place, a plan of action for your tree’s monitoring, health and maintenance.  Edmonton’s Best Arborist can aid you in keeping your trees disease- free and beautiful!