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Plantwise Technical Factsheet

bacterial blight of coffee (Pseudomonas syringae pv. garcae)

Host plants / species affected
Citrus
Coffea (coffee)
Coffea arabica (arabica coffee)
Phaseolus vulgaris (common bean)
Solanum lycopersicum (tomato)
Solanum tuberosum (potato)
List of symptoms/signs
Growing point  -  dieback
Leaves  -  necrotic areas
Stems  -  canker on woody stem
Whole plant  -  plant dead; dieback
Symptoms
The symptoms of BBC differ from typical halo blight of coffee which are more restricted to the leaves. In Kenya, the disease produces water-soaked spots on leaves and angular necrosis of shoot tips, nodes and internodes, spreading rapidly on primary branches. Progressive stages of the disease reveal cankers of the wood of primary branches and the main stem, gradually invading the vascular system of the host. Finally, wilting and desiccation of apparently healthy secondary and tertiary branches occurs (Kairu, 1997). Affected plantations have a fire-scorched appearance.

Prevention and control
In the 1980s, positive and negative side effects of the fungicides controlling coffee berry disease (CBD) on the occurrence of BBC were detected. Copper in most formulations had a reducing effect on BBC, but ortho-difolatan, the major fungicide used for CBD control, stimulated BBC disease. Recommendations to farmers included closer intervals of copper spray applications starting just before the long rains and continuing to the end of the short rains. A total of 13 to 14 sprays per year became common practices in areas where both diseases occurred (Kairu et al., 1985). In the 1990s, spraying schedules were correlated to rainfall data developing a better prognosis system with a consequent reduction in fungicide usage (Kairu, 1991). Through the use of copper sprays the pressure of BBC in infected areas increased, the problem could not be solved using fungicides alone. New formulations of copper-based bactericides came into consideration containing less copper and are recommended with more success (Kairu et al., 1991).

Impact
Losses due to BBC can be as high as 100% of the total crop. After heavy outbreaks, infected trees can be destroyed. In its few areas of occurrence, BBC represents the major pest of coffee diseases in Kenya.

Related treatment support
Pest Management Decision Guides
CABI; CABI, 2014, English language
CABI; CABI, 2017, Portuguese language
 
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