Bacterial blight of coffee is caused by Pseudomonas syringae pv garcae. Symptoms of the disease include oval or circular, brown leaf spots. The spots can have a water-soaked appearance and eventually dry out to yield brown spots, possibly with a yellow halo. As the disease progresses, the shoot tips die and necrosis spreads rapidly down the branches. The leaves can eventually turn black and die off but often remain attached. It is typically an epiphytic pathogen.
General management guidelines for bacterial diseases include cultural and sanitation measures of exclusion and eradication. Propagation programs must include control measures to ensure propagation material (including seeds and cuttings) be of clean, uninfected stock. Eradication processes should include pruning infected twigs and branches during the dry season. Crop rotation does not apply easily to coffee farming, where saplings can take three-to-five years to become economically productive and can remain economically productive for twenty years or more. Coffee-specific management guidelines include application of copper and dithianon sprays for both eradication and protection. Spray application should begin before the rainy season and continue through the season. There are also some antibiotic substances that have proven effective on plants in Brazil. There is at least one known coffee variety (Geisha) that displays some resistance. Caffeine produced by the coffee plant is a natural antibiotic and is known to suppress the growth of P. syringae pv. glycinea and P. syringae pv. tomato.Caffeine likely contributes to the relatively low incidence of bacterial infection in coffee trees.
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