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Bacterial Blight of Coffee

Bacterial Blight of Coffee caused by Pseudomonas siringie cv. garciae makes a leaf and twig blight on coffee plants in East Africa and South America.

Symptoms

Lesions on the leaf beginn as water-soaked spots that turn black and expand. So the leaves become necrotic and curl inwards, but remain attached to the plant. When the terminal bud on the shoot becomes infected, the infection moves down causing dieback. Axial buds on young branches in some distance form the tip are vulnerable to infection too. The lesion can griddle the branch, damaging the vascular tissue and causing the branch above the blackened node to wilt and die. The most typical symptom of heave infestations are blackened tips of branches looking like burned.

Weather situations favouring the Infection

Bacterial blight is most endemic in the higher growing areas like around Mount Elgor, Solai and parts of the Nyeri district in Kenya. Here infections are mostly found after cool nights and most frequent after hail storms where the wounds made by the hail are the entry ports for the bacteria to infect the plants and the leaf wetness left after the hail is giving the moisture for the infection. Optimum temperatures for this disease tend to be around 12 to 25°C. If there is an event allowing the bacteria to infect the coffee tree, the infection severity will be as higher as more inoculum is available.

Bacterial Blight of Coffee  in the FieldClimate bacterial propagation model

For Kisi, Kenya bacterial propagation was quite low during February and increased at the end of February beginning of March with the onset of rains.