• Lecanosticta spp.now recorded in 44 countries, mostly in the northern hemisphere. • L. acicola has increased its range, now found in 24 out of 26 European countries. • Climate change means L. acicola could affect 74% of Pinus forested area by 2100. • Lecanosticta species were recorded on 70 hosts, including Pinus, Cedrus and Picea. • We explore global BSNB management strategies using European Case studies.

Fungal pathogens that benefit from climate change have become more prevalent as a consequence of extended drought periods and higher temperatures. Since the dry and hot years of 2018/2019, the causative agent of sooty bark disease Cryptostroma corticale led to an increasing die back in sycamore forest stands in Germany. Thus, in 2019, spore traps were set up in one forest stand to investigate the dispersal of the pathogen under temporal and spatial aspects. The mortality rate in the study site due to sooty bark disease was quite high: 31% in spring, increasing to 49% in autumn 2019. Quantifying the airborne spores of C. corticale in consecutive periods of the year, a correlation with seasonal aspects was detected. In winter and spring, spore release was relatively low compared with summer months. In summer, high abundances of conidia of C. corticale were released. In July, 399 spores were detected per cm² per day. From June to August, spore release was 12.6 times higher than in springtime. In autumn 2019, a decrease was visible, although the number of conidia was still higher than in spring. The vertical gradient of spore abundances changed over time: the lowest spore release was found along a gradient at 14 m of height in spring, which shifted down to 2 m in autumn. According to our results of spore release, sooty bark disease is strongly driven by the impact of seasonal factors.

Scots pine (Pinus sylvestris), traditionally considered a drought-tolerant species, is increasingly threatened by climatic stress and the opportunistic pathogen Diplodia sapinea in Central Europe. Using linear mixed models, this study investigated the basal area increment (BAI) of 164 trees in Northern Bavaria using tree-ring analysis and the detection of D. sapinea in shoots to investigate whether pathogen detection is associated with radial growth and climate sensitivity. Climate–growth analyses (based on chronologies spanning 82–127 years) identified the summer climatic water balance (CWB, June–August), previous-year spring CWB (March–May), and current-year spring temperatures (February, March) as the main growth drivers. Model results demonstrate a strong size-dependency during the 2003–2023 study period: while small trees in which D. sapinea was detected in shoots (basal area (BA) ≤ 800 cm²) appear to exhibit higher climatic sensitivity than trees without detectable D. sapinea, larger pines (BA ≥ 1500 cm² ≙ DBH ≥ 43.7 cm) exhibited trends pointing toward a near-complete climatic decoupling. These larger trees exhibited a significant growth deficit of −3.69 cm²/year during cold spring conditions (−2 °C) compared to healthy trees. In the largest size class (BA ≥ 2200 cm²), this productivity loss reached its peak at −10.83 cm²/year under high lagged spring water availability (+95 mm CWB in the previous year’s spring). While healthy trees reached an annual BAI of 17 cm²/year under these favorable conditions, infected trees were limited to 10 cm²/year, representing a reduction of approximately 41% and confirming the profound disruption of climatic growth stimuli in mature trees. Our findings indicate that mature pine stands are more vulnerable to productivity losses than predicted by purely abiotic models, although fixed effects explain a limited portion of overall growth variation (marginal R² = 20.81%, compared to a conditional R² = 71.99% including random effects). Consequently, despite high individual-tree and site-level variability, these size-dependent associations with D. sapinea shoot colonization must be increasingly integrated into forest resilience assessments as crucial population-level trends.