EFFECTS OF THREE TETRACYCLINES AND THEIR METHOD OF APPLICATION ON THE DEVELOPMENT OF CLOVER PHYLLODY AND ASTER YELLOWS SYMPTOMS IN ASTER

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Abstract
Single treatments with oxytetracycline, tetracycline, or doxycycline, applied as root dips, foliage dips, or sprays immediately after inoculation, delayed the development of clover phyllody and aster yellows symptoms on aster (Callistephus chinensis Nees). Oxytetracycline and tetracycline were highly effective at 1000 ppm against both diseases, regardless of method of application, but they had phytotoxic effects, ranging from chlorosis and leaf deformation to plant death. Doxycycline at this concentration was highly effective as a leaf dip or spray but caused death of all plants when applied as a root dip. Root dips, foliage dips, and sprays with all three antibiotics at 100 ppm were also effective in delaying development of symptoms of both diseases. At 10 ppm, only doxycycline caused a delay in symptom appearance.