Epsilon Archive for Student Projects

Abstract

Acute Oak Decline (AOD) is an emerging disease affecting oak stands across Europe, associated with symptoms like stem lesions, slime flux, and rapid tree death. This study investigates the occurrence and special distribution of AOD in a Sessile Oak (Quercus petraea) stand in Central Germany, combining a full stand inventory with field assessments and laboratory analysis.

A total of 451 trees were surveyed, recording tree characteristics, mortality, and AOD-associated symptoms. Bark samples out of lesions from 18 trees were analyzed using quantitative qPCR to detect the bacteria Brenneria goodwinii, Gibbsiella quercinecans, and Rahnella victoriana. The mortality in the stand increased to 14.4% of all trees in 2026, and lesions were widespread among living oaks. However, no clear special pattern of symptoms was identified. All three AOD-associated bacteria were detected, particularly in the lower slope part of the area, with B. goodwinii occurring most frequently. The results indicate that AOD is driven by a combination of biotic and abiotic stressors rather than a single causal factor. Drought, pest pressure, and stand conditions likely reduce tree vitality and promote disease development. The findings support the concept of a complex host-microbe interaction, in which B. goodwinii may persist endophytically within the host at low levels, while other bacteria are more associated with the surrounding environment. The pathogenicity of the bacteria seems to be triggered by the interaction of these bacteria in combination with host stress.

Overall, the study highlights the importance of maintaining stand vitality and continued monitoring to better understand and manage AOD in forest ecosystems.