Overhead irrigation may also play a role in spreading the bacteria. Movement of infected plants, seedlings, propagative material, and fruit is the primary means of spreading the canker pathogen over larger distances. Contaminated clothing, tools, packing boxes, and other items associated with harvesting and postharvest handling of fruit are also potential sources of infection. Canker bacteria survive and multiply primarily in naturally occurring lesions. Bacteria may also survive in crevices in the bark tissues of citrus trees.
Bacterial populations appear to decline rapidly in soil.
It has been suggested that the bacterium may survive at low population levels on citrus hosts without symptoms developing, and it may also survive for short periods of time on some weeds and grasses. Neither of these survival mechanisms has been proven, however. When an area is suspected of being infested with citrus canker, fruit or leaf samples are sent for testing by State and Federal laboratories. Outbreaks of citrus canker may also be reduced when windbreaks are constructed in windy areas. When environmental conditions are favorable for the spread of the disease, chemical control measures are not entirely effective.