Black Knot

The bane of the prunus genus, Black Knot is highly infectious, disfiguring and widespread. All the cherries and plums, flowering almond and Mayday Tree may be affected. Identifying Black Knot is easy - the symptom is the appearance of dense black swellings on branches. This is easy to see in winter, and winter (late Fall to very early Spring) is the best time for pruning it out as the fungus is dormant and not producing spores. The pruner should look after their own and their neighbours' trees by properly disposing of diseased branches (burning is best) and disinfecting their tools after use.

For further information with reference to varieties of trees affected, see link below:

http://www.ct.gov/caes/lib/caes/documents/publications/fact_sheets/plant_pathology_and_ecology/black_knot_of_ornamental_plum_and_cherry_4-02-08r.pdf

 

Dutch Elm Disease

Elms are a glory in our city and a tribute to the spirit of those who planted them. Although Dutch Elm Disease is not a problem in Western Canada, strict limitations on pruning are in place to prevent its possible spread:

It is illegal to prune between April 1st and September 30th

 

 

Treatment or prevention options for the birch borer worm?’ 

A: The bronze birch borer is native to North America, and in Canada is found from Newfoundland to British Columbia. This insect targets old and stressed birch trees. They bore under the bark and feed on the tissue of the tree that conducts sap. The borers start at the top of the tree and work their way down. One of the sure signs of borer infestation is that the top of the tree is completely without leaves. The feeding activity of the borer girdles the branches and trunk of the tree. This girdling eventually will choke off the sap flow completely, causing the death of branches and eventually the tree.

The best way to control birch borer is to maintain the health of your trees, as borers will normally not attack healthy trees. Sufficient water for birches is absolutely critical for their health. Birch are trees that are native to rivers, lakes, and other areas with high water levels. They do very poorly in drought conditions. Over the past few years we have had some very dry conditions. It is in the spring that birch trees need the most water. They can draw up hundreds of gallons of water each day. If there is no water reserve in the soil for them to draw on they will go into stress and become very prone to birch borer attack. Watering the birch during the fall to build up the water reserve is critical to their health.

Turn your garden hose to a gentle trickle and place the hose at the base of the birch tree. Let the water trickle out for at least two hours. If you have a soaker hose this is even better. Turn the hose upside down so the holes are facing the ground and turn the water on to a very gentle flow. This type of watering delivers water deeply and helps to keep the roots from drying out during the winter months.

Unfortunately, once a tree is infested with borers it is impossible to eradicate them. Signs to look for include ridging of the bark. You can actually feel the ridges by running your hand along the trunk and/or branches. Another telltale sign are D-shaped holes in the bark, from which the adults emerge. The holes look just like a typewritten D and are of the same size. If a tree exhibits top dieback symptoms then dead branches should be pruned out in the fall 30 to 50 centimetres below either the dead wood or any signs of successful beetle attack (the D-shaped holes). All pruned material should be destroyed to prevent any beetle emergence the following spring.

 


Pruning resources:

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