Non-native pests, climate change, and their interactions are likely to alter relationships between trees and tree-associated organisms with consequences for forest health. To understand and predict such changes, factors structuring tree-associated communities need to be determined. Here, we analysed the data consisting of records of insects and fungi collected from dormant twigs from 155 tree species at 51 botanical gardens or arboreta in 32 countries. Generalized dissimilarity models revealed similar relative importance of studied climatic, host-related and geographic factors on differences in tree-associated communities. Mean annual temperature, phylogenetic distance between hosts and geographic distance between locations were the major drivers of dissimilarities. The increasing importance of high temperatures on differences in studied communities indicate that climate change could affect tree-associated organisms directly and indirectly through host range shifts. Insect and fungal communities were more similar between closely related vs. distant hosts suggesting that host range shifts may facilitate the emergence of new pests. Moreover, dissimilarities among tree-associated communities increased with geographic distance indicating that human-mediated transport may serve as a pathway of the introductions of new pests. The results of this study highlight the need to limit the establishment of tree pests and increase the resilience of forest ecosystems to changes in climate.

Antibiotics are emerging pollutants of great concern, due to detrimental effects of their sublethal concentrations on microbial communities. Monitoring of antibiotics’ presence and concentrations in the aquatic environment is of fundamental importance to the management of water resources. This study was aimed at filling the knowledge gap in terms of presence and concentration of antibiotics in surface water and groundwater in one of the mountain regions in southern Poland. The detailed aims included the assessment of whether there are spatial and/or temporal trends in antibiotic occurrence in water and the investigation of causes behind the changes in antibiotic concentrations. The study was conducted in seven sites (two groundwater and five river water) along the Białka river valley. Antibiotics were subjected to solid-phase extraction, followed by UHPLC/MS detection. Clindamycin, erythromycin, ofloxacin and trimethoprim were the most frequently detected, while the highest concentrations were observed for oxytetracycline and clindamycin. No antibiotics were detected in only one of the groundwater sites. Sewage treatment plant effluent was the hotspot of antibiotic contamination of the river downstream. The detection rates of antibiotics in the examined region seem to be driven mainly by the stability of antibiotics in the environment.

Pyrenochaeta fraxininawas first described in 1913 from the state of New York (USA) on petioles ofFraxinussp. Since then, the species has not been reported from North America and reports from the other regions of the world are very sparse. The results of this study onP.fraxininaare based on the material collected in various regions of Poland from 2012 to 2019. The material comprised 2700 previous year’s leaf petioles ofFraxinus excelsiorand 1970 petioles or leaf residues of eight other deciduous tree species. As a result, the occurrence of pycnidial conidiomata ofP.fraxininawas confirmed onF.excelsior(3.4% of petioles),F.mandshurica(1.5%),F.pennsylvanica(3.2%), andAcer pseudoplatanus(2.0%). The morphology of the microstructures was described based on the fresh material and compared with the holotype ofP.fraxinina. The optimal temperature for the growth of the fungus in vitro was estimated as 20 °C. The analyses based on ITS-LSU rDNA sequences and a protein coding sequence ofTUB2andRPB2genes showed thatP.fraxininaisolates form a well-supported clade in the phylogenetic trees. The species proved to be closely related toNematostoma parasiticum(asexual morphPyrenochaeta parasitica), a species occurring onAbies albain connection with needle browning disease. Interactions betweenP.fraxininaand the ash dieback pathogen,Hymenoscyphus fraxineus, were analyzed in vivo on ash petioles and in vitro in dual cultures. Among 93 petioles ofF.excelsior, for whichP.fraxininaconidiomata were detected, 26 were also colonized byH.fraxineus. Mostly, these two fungi occurred separately, colonizing different sections of a petiole. For all dual cultures, both fungi,P.fraxininaandH.fraxineus, showed growth inhibition toward the counterpartner. The role ofP.fraxininaas a saprotrophic competitor towardH.fraxineusin ash petioles is discussed.

Apiognomonia hystrix is an ascomycetous fungus within Diaporthales that is found on maples and to a lesser extent on other hardwood trees in Europe, Northern America and Asia. To date, varying opinions on the species’ status as a cause of plant diseases have been expressed. In this study, we present the results of analyses conducted from 2012–2017 at forest sites in Poland on the occurrence of A. hystrix on Acer pseudoplatanus and Fraxinus excelsior and the pathogenicity of this fungus towards both tree species. For the sycamore leaves, A. hystrix conidiomata were detected in connection with 19.2% of galls caused by Dasineura vitrina, 20.4% of galls caused by Drisina glutinosa and 67.9% of extensive vein-associated necroses. The A. hystrix colonization of galls caused by both midge species resulted in statistically significantly larger necroses. On European ash leaves, conidiomata of A. hystrix occurred in connection with 0.8% of Dasineura fraxinea galls. Perithecia of A. hystrix were detected on overwintered leaf petioles in 8.1% of A. pseudoplatanus and 1.2% of F. excelsior samples. Twelve representative cultures were characterized molecularly by barcoding three marker genes (ITS, ACT, CAL). Results of phylogenetic analyses indicate that A. hystrix isolates are genetically variable, and three lineages are distinguishable. Eight isolates, including four originating from sycamore and four from European ash, were used to determine A. hystrix pathogenicity. Among the 48 A. pseudoplatanus petioles inoculated with A. hystrix, 41 developed necrotic lesions after 8 weeks, with the average necrosis length caused by particular isolates ranging from 14.5 to 67.2 mm. None of the 48 inoculated F. excelsior petioles developed necrotic lesions. Finally, selected aspects of A. hystrix morphology on natural substrates and in vitro are discussed in this paper, as well as the species’ potential to cause disease symptoms.

Species of Apiognomonia are some of the most ubiquitous leaf-associated fungi of broad-leaved trees of the northern temperate zone. Especially widespread and diverse is Apiognomonia errabunda, found mostly on beech, oak, and linden. This species and its closest relatives are known for their complicated phylogenetic relationships that have caused considerable confusion in the past. In the present paper, we describe the results of a three-gene-based reconstruction of phylogenetic relationships between A. errabunda, A. veneta, and A. hystrix for 373 isolates. Using combined information from the nuc rDNA internal transcribed spacer region ITS1‐5.8S‐ITS2 (ITS barcode) and intron regions of actin (ACT) and calmodulin (CAL) genes for 263 isolates, we confirmed the occurrence of host-associated lineages within A. errabunda. However, the clustering of isolates by host species was incomplete: some isolates occurred on the “wrong” hosts and a number of isolates carried mixed genetic profile, indicating substantial level of inter-host group recombination. In addition, a number of isolates were identified as putative, pending further verification, interspecies hybrids between the much more divergent A. errabunda and A. hystrix.