Control of Pseudomonas syringae with Streptomycin

Abstract

GLASSHOUSE experiments on the control of stone-fruit-blast (Pseudomonas syringae van Hall), a serious disease of stone-fruit trees in New Zealand, have recently been carried out using twenty-three proprietary therapeutants and five antibiotic substances at varying concentrations. Vigorously growing seedling peach trees (Prunus persica Sieb. and Zucc.) were used as test plants. With a sterile needle stems were lightly pricked at fifteen points and then sprayed with treatment solutions. After 1½ hr., by which time all plants were dry, they were sprayed with a 48-hr. beef–peptone–broth culture of a highly pathogenic strain of Ps. syringae and placed for three days in a cabinet at 12° ± 2° C. and approximately 90 per cent relative humidity. Since plants kept for a longer period in this cabinet regularly dropped their leaves, they were removed after three days and placed for seven days in a humidity cabinet where the temperature was 16° ± 6° C. and a water mist was automatically distributed for 35 sec. every 3½ hr. At the end of the ten days, number and length of lesions were recorded. Treatments were repeated on four different dates. By using the above technique a consistently high infection-rate was obtained, lesions developing at more than 85 per cent of damage points on check plants.