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Thursday - March 18, 2010

From: flagstaff, AZ
Region: Southwest
Topic: Diseases and Disorders
Title: Need help with canker in willows in Flagstaff, AZ.
Answered by: Jimmy Mills

QUESTION:

We've got a lot of willows in high altitude desert conditions, irrigated. They've got canker and I want to know if there's anything I can paint on the pruning wounds when I go around trying to remove infected branches. otherwise I'm afraid of the pruning wounds just being new avenues for infection.

ANSWER:

You don't mention the kind of willows that you have (there are 55 species of Salix in our NPIN Data Base), but many seem prone to having canker problems.

Lets look at the pruning paint question first, and then I'll provide some links that might helpful in dealing with the canker problem.

In the past, applying pruning paint to pruned branches was generally thought to be necessary to prevent infectious diseases and infestation by insects. The current thought is that in most cases it is not necessary, and that it may cause more harm than good. Here are a couple of links that support that idea.

Aggie-Horticulture

Tyler Trees

This Bulletin from the Integrated Pest Management Program of the University of Illinois Extension, and this report from the University of Florida have some good information about canker in willows and the fungus that causes it.