This bacterial disease occurs on oaks, elm, hackberry, maple, mulberry, sweetgum, sycamore, and planetree but has been confirmed only on oak species in Illinois. It kills infected trees, even mature oaks, but slowly, over many years. Details about this disease have been discussed in issues no. 13 and 18 of this newsletter (2005).

Bacterial leaf scorch has been confirmed on many of the listed species in Kentucky but only on oak in Illinois. A plant pathology professor in Kentucky (Dr. John Hartman) works with this disease and has actively looked for it in the landscape. It is very possi-ble that we also have other infected species in Illinois. The bacterial pathogen cannot be detected with laboratory isolations or observations with a compound microscope. A special ELISA test (enzyme linked immunosorbant assay) is needed to confirm the presence of the causal bacterium, Xylella fastidiosa. In addition, bacterial leaf scorch symptoms resemble many other problems.

A very good report on bacterial leaf scorch was just published in the online plant pathology journal, APSnet. The feature article for November 2005 is “Bacterial Leaf Scorch of Shade Trees,” by feature editor, Monica Elliott. The article can be viewed at http://www.apsnet.org/. Authors are Ann Gould and James Lashomb from Rutgers University. Read this article (or download it for later reading) to learn as much as you can about this silent killer. There are many helpful images in the article as well.