SURVIVAL OF ERWINIA AMYLOVORA BACTERIA ON PLANT SURFACES AND THEIR ROLE IN EPIDEMIOLOGY
In dried bacterial slime from agar media the bacterial cells are embedded in an enveloping substance, that may protect the cells against adverse effects of desiccation. This substance is water soluble. A similar substance though probably of different composition, is present around bacterial cells in ooze or strands exuded from diseased parts of infected hosts.
Washed, naked, bacterial cells did not survive 24 hours; when embedded only cells stored at 20°C or more died within 1 – 2 days.
At relative humidities higher than 75% the bacteria died within a few hours; when exposed to solar radiation they did not survive for six hours.
Multiplication of bacteria on leaf surfaces could not be demonstrated.
Although the experiments were made with bacteria from culture media, it is suggested that bacteria present on leaf surfaces in orchards originated from freshly exuded ooze on wilting shoots or blossoms will react similar.
So once deposited either naked or as strands or aerosols they will soon die under the influence of the environmental factors studied, in spite of the presence of their protective envelope.