I have a five year old Mountain Ash tree and I have noticed this year that some of the leaves are starting to turn brown and drying out, I'm not sure if it is a disease or an insect problem. I have seen no visible signs of insects on the leaves or tree.

Do you have any suggestions or remedies.

Thank you for your help.

Reply to post by James Gosse, on August 01, 2002 at 16:00:16:

If the leaves are on branches dying from the outside in suspect fireblight, a bacterial disease that can spread quickly but can be controlled by pruning and antibiotic spray like agrimycin.

Reply to post by James Gosse, on August 01, 2002 at 16:00:16:

The symptoms do sound like it may be bacterial fireblight.
While control of the disease through sanitary pruning may help, it is also important to not over-fertilize with nitrogen, and to keep the soil moist.
I assume your tree is the American mountain ash, and not the European species, nor the Showy mountain ash (another native).
I've included several links that offer more information about these trees and their diseases.

http://project.bio.iastate.edu/trees/campustrees/Sorbus_ecology.html

http://www.msue.msu.edu/msue/imp/modzz/00001380.html

http://www.extension.umn.edu/distribution/horticulture/DG0466.html