How to Manage Pests

UC Pest Management Guidelines


Bacterial Blight

Pathogens: Pseudomonas viridiflava and Pseudomonas syringae

(Reviewed 4/13, updated 4/13)

In this Guideline:


Bacterial blight symptoms appear as brown, sunken lesions on the petals that enclose the floral buds. During bud expansion, the petals exhibit a yellow-orange discoloration that later becomes necrotic. The buds fail to mature and abscise. Small yellow leaf spots may occur after summer rains or when overhead irrigation is used. The leaf spot phase occurs along the leaf margins and begins as small, yellow halos 0.04 to 0.08 inch (1 to 2 mm), the center of which becomes necrotic. Later the spots enlarge and coalesce to form large irregular patches (lesions) of necrotic tissue.

Comments on the Disease

Pseudomonas viridiflava and Pseudomonas syringae are widespread plant pathogens that exist on the leaf surfaces of many fruit and vegetable crops. They gain entry into a plant through injured tissues, or when the plant has been predisposed to disease by conditions such as chilling injury or rainfall that favor growth of the bacteria.


Besides avoiding injury to plant tissues, there are currently no cultural practices or chemical controls that are recommended for the control of this disease.


[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Kiwifruit
UC ANR Publication 3449


J. E. Adaskaveg, Plant Pathology, UC Riverside
T. J. Michailides, Plant Pathology, Kearney Ag. Center, Parlier
W. D. Gubler, Plant Pathology, UC Davis

Acknowledgment for contributions to Diseases:
C. Arredondo, Plant Pathology student, UC Davis
K. Conn, Plant Pathology, UC Davis

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