First report of Pseudomonas syringae pv. syringae causing bacterial blister bark on apple in Norway.
In some commercial orchards in southern Norway, apple (Malus domestica) trees developed abnormally in the spring of 2015. The majority of trees affected were of cv. Discovery. It was an unusually cold and wet spring, and many buds did not break or tissue that grew from buds became blighted, typically within 2-3 weeks. The trees exhibited twig lesions with papery brownish blisters forming in the outer bark around buds, on branches or as lesions on the main trunk. Later in the season leaf spots appeared in the orchards with blister bark symptoms. The causal pathogen was isolated and identified as Pseudomonas syringae pv. syringae based on fatty acid, molecular and pathogenicity analyses. This is thought to be the first report of P. syringae pv. syringae causing bacterial blister bark on apple in Norway.