Sunday, August 29, 2010

Some Trees are not worth Saving!

This aspen has a canker disease eating away at its trunk.  The disease invaded the tree through a branch stub at least five years ago as can be seen by the annual growth pattern of the damage. 

The fungus feeds during the winter when the tree is at its weakest.  With the onset of Spring, the tree's vigor improves as leaves emerge and photosynthesis begins.  When sugars reach the injured site new callus tissue forms and stops the spread of the fungus. This callus tissue is invaded and killed as soon as the fungus regains control of the tree.  This cycle happens again and again until the tree no longer has the tissue necessary to keep the tree together.  At some point this tree will break at the canker. 

The fungus that causes this problem, known as Black, Target and Ceratocystis canker, is Ceratocystis fimbriata.

Applying nitrogen around the tree after the leaves emerge in the spring will increase tree health.  Two pounds of nitrogen per 1000 square foot area surrounding the tree is the recommended amount to use.  Unless you have had a soil test conducted that shows phosphorus and/or potassium levels are deficient, these nutrients should NOT be applied.  Ammonium sulfate is a good synthetic nitrogen source to use.  Blood meal, cotton seed meal, corn gluten and other organic products are also good nitrogen fertilizers.

Note:  The cat scratches on the trunks are cause for concern. There is a good chance this fungus will be spread to the other trees by the claws of the cat. Removing the infected trunk will help prevent the spread of the fungus.

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