THE EFFECTS OF STREPTOMYCIN AND TERRAMYCIN, SINGLY AND IN COMBINATION, ON THE LEAF BLIGHT DISEASE OF MAIZE CAUSED BY BACTERIUM CAROTOVORUUM F. ZEAE SABET

Abstract

The growth in vitro of Bacterium carotovorum f. zeae Sabet, the cause of the root and stalk rot and leaf blight disease of maize, was inhibited by dihydrostreptiomycin sulphate and by Terramycin (oxytetracycline). Joint applications showed a synergistic action, and the bacterium was most susceptible to a 1:1 mixture of the two antibiotics. This mixture is effective in checking the development of resistant strains which develop rapidly after treatment with streptomycin alone.Roots of maize seedlings in water cultures, and leaves of older plants readily absorb both antibiotics. High water content of soil favoured absorption; sunlight had no effect. Absorption from leaf applications first increased with higher concentration and frequency of spraying, but after eight daily applications of streptomycin toxic symptoms appeared and there was evidence that the antibiotic was inactivated.Antibiotic treatment of maize leaves shortly before inoculation with B. carotovorum f. zeae reduced the incidence and severity of leaf blight. The therapeutic effect extends at first both downward and upward but later only upward. Treatment of the leaves did not induce resistance to infection in the stems and roots.