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September 29, 2012

1- Bacterial disease in chitalpa looks like drought injury of salt burn.

Yard and Garden September 29, 2012

Q.

I live in Tucson, Arizona and have a chitalpa tree that is growing fine but keeps getting brown spots on the leaves. It does seem to matter if it gets a lot of water or less water. When I brought it, it had them on it also but I thought they would go away with more watering. I love the tree. Is there anything I can do to help it? I would like to buy another one but not sure if they will all have this problem.

Betty P.

A. Although this question came from Arizona, the question and answer are relevant for New Mexico as well.

Your local County Extension agent can help you confirm this (New Mexico State University Extension or University of Arizona Extension), but I suspect your tree is infected with a bacterial disease. The bacterial agent that causes this problem is Xylella fastidiosa. This is a difficult organism to detect, but university diagnostic laboratories have developed procedures to determine if it is indeed infecting the tree.

We had been observing these symptoms in New Mexico for many years, but were unable to detect the bacteria until about 10 years ago. Until we could detect the disease, we assumed it was an irrigation issue.

If the tree does have Xylella, the tree will often survive from several years to many years. The disease often does not express its presence in young trees, but as the tree matures and its growth slows the disease symptoms become apparent. The younger trees are able to "outgrow" the bacteria. If you do not mind maintaining your trees as shrubs, you can prune them severely to rejuvenate the plants. They will often return from severe pruning with very vigorous growth that does not exhibit symptoms of the disease (the disease organism is still present). If the trees were too debilitated when you trimmed them, they may die. Severe pruning will probably reduce flowering in addition to causing the plant to grow as a shrub. So, this may not be an acceptable option for you.

For more gardening information, visit the NMSU Extension publications Web site at http://aces.nmsu.edu/pubs/_h, or to read past articles of Yard and Garden go to http://aces.nmsu.edu/pubs/periodicals.html

Send your gardening questions to:

Yard and Garden, Attn: Dr. Curtis Smith
NMSU Agricultural Science Center
1036 Miller Rd.
SW, Los Lunas, NM 87031.

Curtis W. Smith, Ph.D., is an Extension Horticulture Specialist emeritus with New Mexico State University's Cooperative Extension Service. NMSU and the U.S. Department of Agriculture cooperating