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Calgary Tree Diseases

Calgary trees can be susceptible to many airborne viruses, insect infestations, and diseases. Here is a list of trees most susceptible to disease in Calgary.

Schubert and Mayday trees are often affected by Black Knot.

Mayday, Chokecherry and other trees may be substitutable to black knot fungus. Black Knot is a fungal condition and infects only Prunes species of plants. Black not can be identified by the black mass of growth on the branches of your Mayday or Chokecherry ( Sherbet) trees
The fungal disease rarely kills the tree but if it is not removed it can spread and eventually kill your tree. Many trees live for several years even when they are left untreated. It is best to remove the infected tree limb or branch as soon as you notice the infestation. You can hire an arborist to do the pruning or simply prune the tree yourself. Make sure to prune off and remove infected branches about 2-5" below the affected area and discard the branches in a garbage bag and dispose of them. If you notice your neighbors have infected trees it would be helpful if you notified them about it and encouraged them to have the infected branches removed. Neighboring trees can infect your trees if left untreated.

Birch trees

Birch trees like Cut leaf birch, Dakota pinnacle birch, Weeping birch and other trees can be affected by Birch Leaf miner Birch Leaf miner is similar to the Bronze birch borer, it is the larvae that burrows into the birch leaves in search of nutrients that cause damage to the tree. The leaf miner season begins in late April to mid-May with eggs laid in slits on the upper surfaces of birch leaves. You may see small flat white grubs emerge on the surface of your birch tree leaves. These larvae hatch in June and it is then that they begin feeding on the nutrients of the tree leaves. Eventually, you may see brown spots emerge all over the birch tree leaves. These are dead areas caused by the leaf miner sucking the nutrients out of the tree leaves. Birch leaf miner rarely kills birch trees but it can slow growth and should be treated with insecticide from your local garden center.

Manchurian and Black ash trees

Cottony ash psyllid is a relatively new disease affecting mainly Manchurian and Black Ash. The Ash Psyllid feeds by piercing leaf tissue and utilizing plant juices. All of the damage is done by the immature (nymph) stage and damage can be severe due to feeding nymphs injecting a toxin into tree leaves. These insects feed are hatched in June and July and feed throughout the summer months, often until late August. Adults are highly active and resemble tiny cicadas.
Symptoms include curled or wilted ("cauliflower") leaves and premature leaf drop in summer. Feeding nymphs are surrounded by a cottony material enclosed within the leaf.

If your tree is infested with the cottony ash psyllid, proper timing of treatments is crucial. The soap/permethrin mix works well when applied during the insect's early nymph stage, so treatment should occur in the first week of June and again in the first week of July. Homeowners should monitor trees daily beginning in spring and apply a soap/permethrin mix immediately upon detection of psyllid nymphs and/or the white, cottony material produced by this stage. More than one application may be necessary. Do this again beginning about the first week of July in preparation for the second generation. Once the psyllid adult stage is reached, it is too late and control measures are largely ineffective.

Controlling the cottony ash psyllid

The most effective weapon against this pest is a soap / permethrin treatment known as Trounce®. Because of the lifecycle of this insect, Trounce treatments should commence about the first week of June and again about the first week of July. After that, as the insect matures, it becomes more difficult to treat the tree.


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