A particularly destructive seed-borne disease is halo blight (Pseudomonas syringae). A cool-weather disease, it prefers an ambient temperature of between 16°C and 23°C, but can still occur, albeit with less vigour, if the temperature climbs as high as 26°C.
Overhead irrigation, the method used by most bean producers, greatly increases the chance of infection, as does a moist climate. Take all necessary precautions in these instances.
If the disease strikes, do not replant beans in that land for two years. In addition, incorporate the crop residue into the soil. Once halo blight appears, it spreads rapidly. Thunderstorms with driving rain can accelerate the spread, as can traffic, including tractors and people, through the land.
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October 25, 2019