Bacterial leaf scorch (BLS), caused by Xylella fastidiosa, was confirmed in Illinois a few years ago on oak. Although it may occur on elm, oak, sycamore, mulberry, sweetgum, sugar maple, and red maple, it has been confirmed through the Plant Clinic in Illinois only on pin, shingle, and bur oak species. Clinic samples are sent to a private testing lab in Indiana--Agdia, Inc. There an ELISA (enzyme-linked immuno-sorbent assay) test can be performed on the fresh stem, leaf, and petiole tissues. Agdia lists a large host range for Xylella fastidiosa, including at least 28 families of both monocots and dicots.

In 2003, the Plant Clinic sent nine Illinois oak samples to Agdia for BLS testing. Six were positive, including red and pin oaks from Champaign County and a white oak from Cook County. Why should we be concerned if BLS is present in Illinois? This disease is not just an aesthetic problem to a tree. It can kill a mature tree in 3 to 6 years. Read the details about this disease in issue 13 and learn to recognize the symptoms of BLS.