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Bacterial Leaf Scorch (BLS) Update

November 21, 2006
This vascular disease has begun to show its effect on many tree species in the Midwest. The causal pathogen is a bacterium, Xylella fastidiosa. Unfortunately, this bacterium cannot be identified in the lab as easily as most other bacteria. The current diagnostic test used for confirmation of bacterial leaf scorch is an ELISA (enzyme-linked immunosorbant assay) test on the newest stem growth and leaf petioles of symptomatic tissue. Issues no. 14 and 16 of this newsletter cover most of the basic facts.

Over the last 5 years, the University of Illinois Plant Clinic has confirmed bacterial leaf scorch on pin, red, shingle, bur, and white oaks in Illinois. Other species that may be infected but have not yet been confirmed in Illinois include sweetgum, sycamore, planetree, hackberry, American elm, and red mulberry. Watch for scorch symptoms on these trees, and follow recommended testing practices if scorching appears in mid- to late summer, and scorching intensifies and spreads within a tree for several consecutive years.

Samples have been submitted to the University of Illinois Plant Clinic over the past 5 or 6 years. Bacterial leaf scorch has been confirmed in Illinois in the following counties: Champaign, Iroquois, Jefferson, Sangamon, St. Clair, and Vermilion. All of these confirmations involved oaks.

Author: Nancy Pataky


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