Several mycoplasma diseases of woody plants are known to occur in Korea. These are, Paulownia (Paulownia tomentose) witches´ broom, jujube (Zizyphus jujuba) witches´ broom, mulberry (Morus alba) dwarf, sumack (Rhus javanica) witches´ broom and bush clover (Lespedeza cyrtobotrya) witches´ broom. Of these, Paulownia witch´ broom, jujube witches´ broom and mulberry dwarf are economically important, causing heavy mortality of the host trees in numerous isolated areas throughout the country and often devastating large tracts. Today, mycoplasma disease has become the major factor limiting the successful cultivation of Paulownia, jujube, and mulberry in Korea. Consequently, in the last several years, much research has been directed toward the prevention and control of the diseases. Preventive measures such as (1) propagation by root cuttings or suckers from disease-free areas, (2) propagation of seedlings from true seeds, (3) immediate removal of diseased individual trees from the field as soon as they are detected, and (4) control of insect vectors by spraying insecticides, are recommended for preventing the spread of the diseases. However, such preventive measures alone often have failed to prevent the natural spread of the diseases because of the difficulties in controlling the insect vectors in field plantings. Besides, these control measures do not cure the etres already infected, and removal of the valuable trees is ultimately necessary, resulting in considerable economic loss to the growers. Therefore, along with recommended preventive measures, direct control of the mycoplasma diseases by chemical therapy using oxtetracyclines applied to trees by trunk or root injections are also used where it is effective and economically feasible. Currently, trunk injection of oxytetracycline is extensively used for the control of jujube witches´ broom in Korea and saves many thousands of valuable jujube trees every year.
Knowledge andinformation on plant mycoplasma diseases of forest trees is steadily increasing. Nevertheless, our present knowledge on plant mycoplasma is comparatively limited. Increased research efforts to better understand the nature of the mycoplasmas and the disease they cause, as well as the interelationships among the known mycoplasma diseases of plants, would ultimately lead to the development of more effective control measures for the mycoplasma diseases of forest trees. The present status of mycoplasma diseases of woody plants in Korea will be discussed.
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