Redbud Leaf Spots

Help for the Home Gardener from the CCMG Help Desk

Client Question:
The client brought a leaf sample into the Help Desk. The leaf was from a Redbud tree. It was covered with spots. The client wondered if we could help with diagnosis and treatment of the problem.

CCMG Help Desk Response:
The spots on the leaf are most likely caused by a fungus, Cercospora. The web page at http://bit.ly/ZePPMa was generated from a Google search of “cercospora leaf spot redbud” It has photos which you could check to see if they look like your problem.

It looks like your tree is an Eastern Redbud (Cercis canadensis). My research indicates that Cercospora is a known problem of this specie. However our University of California information does not list this. Here is the UC page with some additional Redbud information, although you will notice that the leaf they show is the Western variety which is a little different. http://www.ipm.ucdavis.edu/PMG/GARDEN/PLANTS/redbud.html. Even though UC doesn't list such leaf spots on the Western Redbud (Cercis occidentalis), most Western Redbuds in my neighborhood exhibit similar leaf spot problems.

The good news is that most fungal diseases, including Cercospora, will not seriously damage the tree, but it will not look its best at times, including the loss of some leaves. The best way to manage this is to give the tree good cultural care, as stressed trees are more susceptible to problems. Eastern Redbuds, being originally from the Eastern U.S., need regular water and good drainage, so you should water when the top 2 inches of soil are dry, but not so much that the soil stays wet. A several inch layer of mulch out to several feet past the drip line of the tree will help, but make sure the soil close to the trunk is clear of mulch. Also using drip or soaker type irrigation near the drip line will help; to keep the leaves dry, you should not use overhead watering. If the foliage is thick you can lightly prune out the tree to improve air flow, and you can prune off and discard any dead wood and badly affected leaves to remove some of the fungal material. Clean up fallen leaves and debris under the tree as the fungus can survive in fallen leaves and twigs. You should avoid over fertilizing, as new growth is more susceptible to diseases. Anti-fungal sprays are not usually recommended in the home garden and are not usually helpful.

Like most landscape trees, they sometimes have their minor problems, but with some minimal care, the Eastern Redbud is a beautiful and useful garden tree that can add significantly to your home landscape.

Contra Costa Master Gardeners Help Desk 

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Editor's Note: The Contra Costa Master Gardener Help Desk is available year-round to answer your gardening questions.  Except for a few holidays, we're open every week, Monday through Thursday from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA  94523.

We can also be reached via telephone:  (925) 646-6586, email: ccmg@ucanr.edu, and we are on the web at http://ccmg.ucanr.edu/