Cankers and galls on shrubs

Wed. Jan. 31, 2018

Click below to listen to my 2 min. Garden Bite radio show:  Cankers and galls on shrubs

Do you suffer from galls or cankers?

I just have to grin when I hear that.  The thought of some medication commercial coming up with side effects so horrific, I’d rather have a canker!  Maybe …

cytospora-canker UofMN ext.

With all the leaves gone on our trees and shrubs, it’s a good time to take a careful look at their branches for galls or cankers.

Cankers and Galls [University of Minnesota Extension] This link will take you to a wealth of information!

Black Knot

Look for black knot cankers on your plums and cherries.  They start out the same color as the stem, then turn black, crack open and release infectious spores.  Prune these branches out below the knots.  Burn or bury cankered branches.  This will help considerably in disease management.  Never compost any diseased plant.

Check your viburnum, euonymus and spirea for round, swollen growths.  These are called galls and will eventually girdle and kill the stem.  Prune these out and destroy them.  Also, clean your pruners in between cuts with rubbing alcohol or Lysol.

There are numerous types of cankers and galls caused by a variety of reasons.  The important thing to remember is that they cut off the water and nutrient flow to the branch, girdling it.  This will eventually kill the tree.

Pine oak rust gall

This is also a good time to consider doing a little pruning to shape your trees or shrubs. Opening them up to better air circulation is good disease management.  It also allows for more sunlight. There may be a tree that’s giving more shade than you want, consider pruning it now as well. Send me your questions, suggestions and comments at and find Garden Bite on Facebook.