Symptoms on leaves are often irregular in shape and, as is the case for BLS, may include a yellow or red "band" between green and scorched tissues (Fig. Plant infection by living or biotic agents (such as fungi, bacteria, nematodes, and viruses) can also result in leaf scorching, but this type of scorching is not clearly defined on the plant. Note that most leaves are affected in a uniform pattern. Leaf scorch of weeping beech caused by abiotic (environmental) stress. In most cases, this type of scorching is fairly uniform around leaf edges, affects newer leaves as well as older leaves, will appear on vast expanses of the canopy, and may also develop soon after a known stress (such as drought or a salt application) occurs (Fig. Abiotic (or environmental) stresses that can cause leaves to scorch include moisture extremes, wind, salt, air pollutants, toxic metals, and nutrient extremes. Leaf scorch in plants can be attributed to biotic agents or abiotic stresses (10). It will finish with a discussion on disease management and the historical and current significance of X. This article will describe and illustrate symptoms of BLS, discuss the unique bacterium that causes the disease, and explain disease development. 1 Scientific nameġ For a more complete list of alternative hosts, refer to the Some alternative hosts of Xylella fastidiosa. salicina)Ĭitrus variegated chlorosis ( Citrus spp.) Pierce’s disease of grapevine ( Vitis spp.) Xylella fastidiosa characterized by the primary symptom expressed. Some of the economically important diseases caused by Shade tree hosts affected by BLS (25,33). fastidiosa lives in the xylem tissues of host plants, and the bacterium is transmitted (or vectored) by insects that feed on xylem fluid, such as leafhoppers or sharpshooters (17). fastidiosa also resides in "alternative" hosts, many of them common landscape ornamentals and weeds, where no discernible symptoms of disease may occur (Table 3) (19). This bacterial pathogen is distributed throughout the Western Hemisphere, has a very wide host range, and causes diseases with two basic types of symptomology (leaf scorch or stunt) in a number of economically important hosts (Table 2). The disease has been identified in the urban forest (landscapes, street plantings, and small woodlots) throughout the eastern United States and as far west as Texas.īLS is one of a group of diseases caused by Xylella fastidiosa. Gould)īacterial leaf scorch (BLS) affects many different shade tree species such as American elm, red maple, sweet gum, sycamore and London plane, and a number of species of oak (Fig. Look for a pronounced marginal discoloration with a dull red or yellow halo between scorched and green tissues. Bacterial leaf scorch of oak ( Quercus rubra). Department of Plant Biology and Pathology
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