Bacteria were isolated from necrotic lesions on a horse chestnut tree (Aesculus hippocastanum) with bleeding canker in Hamburg, Germany. Sequencing of the rDNA-ITS region revealed great similarity to pathovars of Pseudomonas syringae. Pseudomonas syringae pv. aesculi was identified by sequence homology of the gyrase B gene. This is the first report of P. syringae pv. aesculi in Germany. Phytophthora was not detected.

Trees are valuable for urban areas, however, are also susceptible to wood rot fungi. For accurate and fast assessment of the severity and evolution of decay in standing trees, a molecular technique was used to identify the causal agents of wood rot. Fruit bodies of wood decay fungi were collected from infected trees in various stands in Germany. Thirty-six species were identified by traditional methods. The DNA of fruit bodies was extracted, ITS-rDNA amplified by PCR, and ITS regions sequenced. Wood samples from infected urban trees were collected, the entire DNA extracted from affected wood parts, and fungal ITS amplified and sequenced. Fungal species were identified by comparing sequence data with the fruit body data. The technique enables an accurate and rapid identification of causal rot fungi in urban trees.

Tree care, especially pruning, is still mostly done in the dormant time. Such treatments expose live inner bark, the vascular cambium, and functioning outer sapwood to harsh external influences followed often by infection of pathogens. Investigations about response reactions of beech and oak to wounding made in different times of the year showed that wound closure was significantly slower for December and February wounds than in April and October. The length of discoloured sapwood was in October and December wounds greater than in February and April. Sapwood reaction expressed by the soluble phenol concentration index indicated however no significant differences among wounding dates. Overall, woundings in the vegetation period will be more effectively compartmentalized than in the dormant season. Consequently, tree care like pruning with many woundings should not be done in the winter period.

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