COMMON NAME: Bacterial Leaf Scorch (BLS) of elm.
SCIENTIFIC NAME: Xylella fastidiosa subsp.multiplex, a gram-negative bacterium (genus Xylella, family, Xanthomonadaceae).
In Texas, infection of cedar elm with X. fastidiosa subsp. multiplex is a common occurrence, and, like with the other common BLS diseases in this series, water stress is probably a synergistic factor.
SYMPTOMS: BLS is identified by a characteristic marginal leaf scorch. Symptoms progress from older to younger leaves and affected leaves may curl and drop prematurely. As the disease progresses over several years, branches die and the tree declines. Elms may be killed outright by BLS.
BIOLOGY: The bacterium is spread by insect vectors. Both adult and nymphs acquire the bacterium when feed on succulent tissues of infected hosts. The bacterium produces biofilms. The disease is limited by low temperatures and plant stress is probably involved to some degree in disease manifestation
MANAGEMENT METHODS: There is no cure for BLS once the bacteria is present but some practices allow to maintain plant healthy. Proper diagnosis is critical for the management of the disease. The disease can be controlled by vector (glassy winged sharpshooter) management with insecticides, but this approach is usually impractical on landscape trees in urban environments. Antibiotic (oxytetracycline) trunk injections are another option, but their therapeutic effects may be only temporary. Other methods include; maintain plant vigor by controlling other pests and diseases, and maintain proper fertilization and irrigation practices.
This factsheet is authored by Ashrafou Ouro-Djobo (Masters PLPM)
Factsheet information for the plant health issues represented by the images on the 2019 TPDDL calendar were written by graduate students enrolled in the Department of Plant Pathology & Microbiology PLPA601 Introductory Plant Pathology course in the 2018 Fall semester (course instructor: Dr. David Appel). This exercise provides an opportunity for a high impact learning activity where the students are tasked with producing an informational output directed to the general public and to provide opportunity for the students to write.