6 - Mycoplasmas

Abstract

The mycoplasmas are the parasites of plants and animals. This chapter discusses the mechanisms by which mycoplasmas cause tree diseases. Mycoplasmas have limited mobility; however, they are able to utilize the vascular system of the host plant to move throughout the host plant. Large numbers of mycoplasmas are often found in the phloem. They occur in the sieve elements of the tissue and may interfere with the movement of sugars through the plant. Leafhoppers are the most common vectors of mycoplasmas. The symptom of mycoplasma diseases appears to be a progressive decline that eventually results in death of the host in a few months to several years. The decline may be associated with any or all of the symptoms including chlorotic foliage, little terminal growth or stunting, the progressive dieback of branches, the lack of flowering, and the necrosis of phloem tissues. The chapter discusses the treatment of trees infected with mycoplasmas. Mycoplasmas as a group are sensitive to tetracycline antibiotics. Tetracycline antibiotics have been used with various degrees of success to control many mycoplasma diseases of plants.