First record of brown spot needle blight (BSNB) caused by Lecanosticta acicola on Pinus mugo in Finland

First record of brown spot needle blight (BSNB) caused by Lecanosticta acicola on Pinus mugo in Finland | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Short Report First record of brown spot needle blight (BSNB) caused by Lecanosticta acicola on Pinus mugo in Finland Eeva Terhonen, Trifković Miloš, Poimala Anna This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8637135/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 6 You are reading this latest preprint version Abstract Climate change has already been acknowledged to have destabilizing effects on tree health. In addition to increased abiotic disturbances, trees are increasingly negatively impacted by the emergence of fungal pathogens. Lecanosticta acicola , the causal agent of brown spot needle blight (BSNB), affects pines and is considered invasive in Europe. In October 2025, typical symptoms of L. acicola , brown circumferential lesions with a yellow halo, were observed on an urban tree, Pinus mugo . The pathogen was isolated from surface-sterilized needles, and morphological and molecular identification confirmed it as L. acicola . Here, we report the first observation of the invasive pathogen L. acicola on the non-native host P. mugo in Finland. Lecanosticta acicola is classified as a Quality Plant Pest by the Finnish Food Authority and as no suitable plant protection methods are currently available in Finland, this finding is of particular significance. The detection of this pathogen highlights a potential threat to forestry and emphasizes the need for preventive strategies to limit its spread, including eradication, resistance breeding and improved integrated pest management (IPM) practices in nurseries. climate change emerging invasive pathogen Mycosphaerella dearnessii Scots pine Figures Figure 1 Figure 2 Figure 3 Introduction Recent evidence indicates that current environmental trends are increasing the risk of large-scale climate system instability (Ripple et al., 2024 ). Climate change is a key driver of emerging and invasive forest disturbances, particularly by favouring fungal pathogens. Rising temperatures facilitate the expansion of pathogen geographic ranges, allowing species previously restricted by cold climates to establish in new regions (Dudney et al., 2021 ; Li et al., 2023 ; Singh et al., 2023 ; Terhonen et al., 2025a ). This process promotes the introduction of novel disease agents into forest ecosystems, where native host species often lack effective resistance (Barnes et al., 2018 ; George et al., 2022 ). In addition, warmer conditions, such as milder winters, enhance pathogen overwintering success and increase infection pressure (Hanso & Drenkhan, 2013 ; Ma et al., 2015 ; Caballol et al., 2022 ). Climatic variables, particularly temperature and precipitation, are therefore major determinants of the global distribution of phytopathogenic fungi (Větrovský et al., 2019 ; Li et al., 2023 ), and their diversity and invasion potential are expected to increase in forest ecosystems under future climate scenarios. Lecanosticta acicola is the causal agent of brown spot needle blight (BSNB). Symptoms appear, as name indicates, brown spots with a yellow halo that encircle the needle (Fig. 1 a), that can lead to necrosis at the distal end (Fig. 1 b). In the necrotic tissue the fungus forms black stromata. Finally, L. acicola produces oval, black fruiting bodies (acervuli-like) bearing conidia that emerge through the epidermis. The conidia are subhyaline to dark olive-green and thick-walled (Fig. 1 c). They have a rounded tip and a truncated base, vary in shape from fusiform to cylindrical, and range from straight to slightly curved (Fig. 1 c). Heavily infected pine trees often retain only the current year’s needles on twigs (Fig. 1 d). Repeated infections can cause extensive needle shedding and, in severe cases, the death of pine trees (van der Nest et al., 2019 ). The disease, BSNB, became widely recognized in the early 1900s after it caused severe damage to longleaf pine ( Pinus palustris ) forests in the southeastern United States (de Thümen, 1878 ; Siggers, 1944 ; Sinclair & Lyon, 2005 ). Beginning in the 1990s, BSNB also emerged in many European countries (van der Nest et al., 2019 ; Laas et al. 2022 ; Tubby et al., 2023 ). In Europe, L. acicola is considered an invasive species, with evidence of multiple independent introduction events (Janoušek et al., 2016 ; Laas et al., 2022 ; Tubby et al., 2023 ). Human activity has likely played a significant role in its spread across the continent (Janoušek et al., 2016 ; van der Nest et al., 2019 ). The pathogen has been recorded since the 2000s on several pine species (such as P. nigra, P. uncinata, P. ponderosa, P. pumila and P. halepensis) in 24 European countries (Tubby et al., 2023 ). However, the most severe and repeated outbreaks have occurred on Pinus mugo (van der Nest et al., 2019 ; Tubby et al., 2023 ). Lecanosticta acicola has also been confirmed on Scots pine ( Pinus sylvestris ) (Adamson et al., 2018 ; Klaviņa et al., 2025). Distribution modelling suggests that L. acicola is likely to become increasingly established in Europe—including Finland—under future climate scenarios (Ogris et al., 2023 ). Given the economic, cultural, and ecological importance of Scots pine, L. acicola should be considered a potential and emerging threat to Finnish pine-dominated forests. Young stands and nurseries are particularly vulnerable, which would affect forest regeneration success and facilitate the spread of the disease into new areas. Attempts to detect L. acicola in Finland have been made previously (Tubby et al., 2023 ), but without success. Symptomatic needles of Pinus spp. have been tested at the Natural Resources Institute Finland, and in October 2025 L. acicola was detected for the first time in Finland in symptomatic non-native P. mugo . Material and Methods In October 2025, needle cast of older needles and brown needle spots were observed on P. mugo in southwest Finland (60°22'59.16''N, 23°7'59.16''E). The tree was growing as urban ornamental in front of a building (Fig. 1 d). Needles with brown spots and yellow halo were collected for analysis (Fig. 1 a). The needles were surface-sterilized with 70% EtOH, air-dried, and then surface-sterilized for 1 min in 2.4% NaOCl, followed by three rinses in DDW. Needles were cut into ~ 1 cm pieces, placed on 2% MEA, and incubated at + 15°C in darkness for 3 weeks. All fast-growing fungi were discarded. Slowly growing black hyphae surrounded by white hyphae emerging from the brown spots (Fig. 1 e) were subcultured, and the conidia were examined microscopically (Fig. 1 c). Representative strains are stored on MEA slants at 4°C at the Natural Resources Institute Finland (Luke). Molecular identification based on the ITS region was performed following Terhonen ( 2023 ). Briefly, DNA was isolated using the PrepMan™ Ultra Sample Preparation Reagent (Applied Biosystems, Foster City, CA, USA) according to Linnakoski et al. ( 2016 ). The ITS1–5.8S–ITS2 region of rDNA was amplified using the primer pair ITS1-F (White et al., 1990 ) and ITS4 (Gardes & Bruns, 1993 ). The PCR mixture contained DreamTaq Green Mix (2×) (Thermo Scientific™), 200 µM dNTPs, 0.5 µM of each primer, and 1 µl of crude template DNA; the reaction volume was adjusted to 15 µl with autoclaved MQ H₂O. PCR conditions were: 94°C for 3 min; 30 cycles of 94°C for 30 s, 55°C for 1 min, 72°C for 1 min; and a final extension at 72°C for 10 min. PCR products were visualised under UV light on 1.5% agarose gel (Ethidium Bromide staining) and purified using the EXO-SAP protocol (Exonuclease I and Shrimp Alkaline Phosphatase; Thermo Fisher Scientific, Waltham, MA, USA) (Linnakoski et al., 2016 ) and sequenced using the ITS1 primer at Macrogen (Germany). The β-tubulin region was amplified using the primer pairs Btub2Fd and Btub4Rd (Woudenberg et al., 2009 ). Polymerase chain reaction (PCR) was performed using the Phire Plant Direct PCR Master Mix (F160S, Thermo Scientific®, Thermo Fisher Scientific), following the manufacturer’s instructions. PCR cycling conditions were as follows: initial denaturation at 98°C for 30 s; 30 cycles of 98°C for 5 s, 60°C for 5 s, and 72°C for 5 s; followed by a final extension at 72°C for 1 min. PCR products were visualised under UV light on a 1–1.2% agarose gel stained with DNA Stain G (SERVA Electrophoresis GmbH, Heidelberg, Germany). PCR products were purified using the Monarch® PCR & DNA Cleanup Kit (5 µg) (New England Biolabs, Ipswich, MA, USA) according to the manufacturer’s instructions and sent to Eurofins Genomics (Germany) for Sanger sequencing in both directions. ITS and β-tubulin sequences were analysed using MEGA12 (Kumar et al., 2024 ). Sequence identity was verified by aligning the obtained sequences with reference sequences in the GenBank database via NCBI BLAST (Altschul et al., 1990 ; Sayers et al., 2025 ). The ITS (550 b) and β-tubulin (445 b) sequences were deposited in the European Nucleotide Archive (ENA) under accessions OZ373024 and OZ387206, respectively. The ITS and β-tubulin sequences, along with the corresponding BLAST results, are available at Zenodo (DOI: 10.5281/zenodo.17951324 ). Phylogenetic analysis Sequences were aligned using the MUSCLE algorithm (Edgar, 2004 ) implemented in Unipro UGENE v53.0 (Okonechnikov et al., 2012 ). The resulting alignment was inspected and manually refined where necessary. Phylogenetic placement of the fungal isolates was inferred using maximum likelihood (ML) analysis in raxmlGUI v2.0 (Edler et al., 2021 ), implementing RAxML with a GTR + Gamma + I nucleotide substitution model. ML analyses were performed in 10 independent runs, and branch support was assessed using thorough bootstrap analysis with 1,000 replicates. The resulting phylogenetic tree was visualised in FigTree v1.4.4 and subsequently edited using graphical softwares. Phylogenetic trees were constructed using a combination of the ITS and β-tubulin regions, as well as the ITS region alone. GenBank accession numbers for the strains used are provided in the Supplementary File. Results Four strains of L. acicola were isolated from brown spots on still-living, surface-sterilized needles. Morphological identification was performed based on conidial characteristics (Fig. 1 d; EPPO Bulletin 2015), and species identity was confirmed for all four strains using ITS rDNA sequencing and β-tubulin (DOI: 10.5281/zenodo.17951324 ). The ITS region showed a 100% identity (537/537 bp; 100% query coverage) with TYPE strain of L. acicola (GenBank accession NR_120239.1), while the β-tubulin gene sequence exhibited a 100% identity (326/326 bp; 71% query coverage) with TYPE strain of L. acicola (GenBank accession KC013008.1). Only reliable regions of the ITS and β-tubulin sequences were submitted to GenBank, and these were identical among all isolates. The phylogenetic analysis further confirmed the species as L. acicola (Fig. 2 , 3 ). Discussion This study reports the first occurrence of brown spot needle blight (BSNB) in Finland. The causal agent, L. acicola , has not previously been recorded in the country. Recent findings show that the pathogen can shift from exotic to native hosts, including Scots pine, and may establish in local pine populations (Adamson et al., 2018 ; Klaviņa et al., 2025). Although the present detection concerns a non-native P. mugo , the establishment of L. acicola suggests that Finnish conditions may permit its survival and potential spread to native Scots pine (Adamson et al., 2018 ; Ogris et al., 2023 ; Klavina et al., 2025). Scots pine accounts for approximately 50% of the total growing stock volume in Finland (1,250 million m³; Korhonen et al., 2024 ), and by the end of October 2025, the average stumpage price for pine logs was €155 (Natural Resources Institute Finland, statistical database). Beyond its economic role in the forest industry, Scots pine is also a culturally significant species, forming an iconic element of Finland’s forest landscapes. Ecologically, its importance is considerable: Finland hosts only around 30 native tree species, and Scots pine contributes substantially to forest structure, biodiversity, and ecosystem functioning. In Europe, several eradication attempts have been implemented to prevent the establishment and spread of L. acicola (see case studies in Tubby et al., 2023 ). Despite eradication efforts, L. acicola has spread from non-native pine hosts (Adamson et al., 2015 ) to native Scots pine eight years after its initial detection (Adamson et al., 2018 ). EPPO lists L. acicola as an A2 pest (EPPO code SCIRAC), indicating that it is present in the EPPO region, but is recommended for regulation as a quarantine pest in member countries to limit its further spread (see PM1/002(34)). Lecanosticta acicola is classified as a Quality Plant Pest by the Finnish Food Authority so this pathogen must not be present in any plants sold in Finland, making L. acicola a significant concern for seedling production and trade (see case study 3 in Tubby et al. ( 2023 )). At the same time, future availability and effectiveness of control methods are uncertain. In Finland, three fungicidal active substances—azoxystrobin (authorised until 02 August 2026), benzovindiflupyr (authorised until 2 August 2026), and prothioconazole (authorised until 15 August 2026)—are currently approved for use in forest nurseries against needle cast diseases. However, first, it is unknown whether these substances are effective against L. acicola ; second, fungicidal active substances are continuously evaluated in the EU, and some may be withdrawn if they are not reapproved. Additionally, no compensation is provided for discarded seedlings for nursery producers (see case study 3 in Tubby et al., 2023 ). There is an urgent need for research to ensure preparedness for the potential spread of L. acicola , particularly to evaluate how effective integrated pest management (IPM) strategies in forest nurseries could prevent infections. When combined with tree breeding, such approaches may provide viable solutions to control and limit pathogen spread. Scots pine exhibits substantial genetic variation, with heritable traits differing among regions, enabling populations to adapt to local environmental conditions (Kujala et al. 2017 ; Savolainen et al. 2007 ; Pyhäjärvi et al. 2019 ). Harnessing this genetic diversity in targeted breeding programs represents an opportunity to reduce any disease impacts. Accordingly, future research should focus on identifying the genetics and heritability underlying possible resistance, thereby enabling effective resistance breeding programs in pines (Fraser et al. 2015, Terhonen et al. 2025b ). Together with eradication measures and nursery-based IPM, these strategies could provide effective means to restrict the spread of the invasive pathogen L. acicola in Finland. Overall, tree health should be communicated more effectively to citizens, who can play a valuable role in helping researchers detect new threats (Terhonen et al. 2025a ). Keeping trees healthy requires combined efforts from policymakers, researchers, government, and the public. Declarations The authors declare that there is no conflict of interest. Acknowledgements This work was supported via Horizon Europe IA project Precilience (Grant Agreement 101157094) and Natural Resources Institute Finland (Luke). Miloš Trifković was supported by the Specific University Research Fund of the Faculty of Forestry and Wood Technology, Mendel University in Brno (grant No LDF_VP_2019021). Linda Mutanen and Tuija Hytönen are acknowledged for their help with the laboratory work. References Adamson, K., Drenkhan, R. and Hanso, M. 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Persoonia 22: 56–62. https://doi.org/10.3767/003158509X427808 Supplementary Files GenBankaccessionstrainsphylogenetics.xlsx Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Minor revisions 27 Mar, 2026 Reviewers agreed at journal 10 Feb, 2026 Reviewers invited by journal 10 Feb, 2026 Editor invited by journal 21 Jan, 2026 Editor assigned by journal 21 Jan, 2026 First submitted to journal 18 Jan, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8637135","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Short Report","associatedPublications":[],"authors":[{"id":588832991,"identity":"55e15569-441c-43e0-bdb4-6fa58ef7e11d","order_by":0,"name":"Eeva Terhonen","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA6UlEQVRIiWNgGAWjYDADAzBZYcEgAaQ+JBBUnwDTckYCpIVxBvFaGNugWvAp5mfvMfzA+MMm35y99+DjwnkSiTPbGxgbHuDRItlzxliCISHNcmfPuWTjmdskEmfzHGBswOcwgxtpCUAthw0MbuSYSfMCtcyTSGB/gE+L/f1nyT8YEv6DtJj/5p0D1CL/gIAtEszHgLYcANvCzNsAdJgEA34tEmeSj1kkpCUbGJw5YyzNc0zCeGZPYiNeLfztB5tvfLCxMzA43mP4mafGRnbG8cMHG3/g0QIGaGYyNhDSMApGwSgYBaOAAAAAdNZL1RhEYaAAAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0002-9288-440X","institution":"Natural Resources Institute Finland: Luonnonvarakeskus","correspondingAuthor":true,"prefix":"","firstName":"Eeva","middleName":"","lastName":"Terhonen","suffix":""},{"id":588832992,"identity":"f4c8df2c-acdc-4354-8d2f-66d6b2f7a631","order_by":1,"name":"Trifković Miloš","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Trifković","middleName":"","lastName":"Miloš","suffix":""},{"id":588832994,"identity":"9479a846-ce7f-4bcb-81cc-96cc4df0ca72","order_by":2,"name":"Poimala Anna","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Poimala","middleName":"","lastName":"Anna","suffix":""}],"badges":[],"createdAt":"2026-01-19 08:52:40","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8637135/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8637135/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":102604784,"identity":"270958d5-a9a4-4152-8cf3-870f8559c60c","added_by":"auto","created_at":"2026-02-13 13:48:53","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1215762,"visible":true,"origin":"","legend":"\u003cp\u003ea) Typical symptoms of brown spot needle blight (BSNB) caused by \u003cem\u003eLecanosticta acicola\u003c/em\u003e, documented in Finland in October 2025. Characteristic brown spots with a yellow halo encircle the needle. b) As the disease progresses, needles die from the lesion outward toward the tip, while the current year’s needles remain alive, creating the characteristic “lion’s tail” appearance. \u003cem\u003ePinus mugo\u003c/em\u003e with BSNB symptoms in Tartu, Estonia (June 2023). c) Conidia of \u003cem\u003eL. acicola\u003c/em\u003e observed under the microscope (60×), displaying the characteristic curved, 1–5-septate morphology. d) \u003cem\u003ePinus mugo\u003c/em\u003e growing as a city tree in Southwest Finland showing needle cast on older needles and typical BSNB symptoms on part of the current-year needles. e) Hyphae growing from a brown spot on the needle (10×).\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8637135/v1/c48d4dfc3d2a8a45f641c67b.png"},{"id":102604787,"identity":"2b088e98-e627-40c7-8152-6c2326cb9db1","added_by":"auto","created_at":"2026-02-13 13:48:54","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":231966,"visible":true,"origin":"","legend":"\u003cp\u003ePhylogram based on maximum likelihood analysis of ITS and β-tubulin sequence data from \u003cem\u003eLecanosticta acicola\u003c/em\u003e and closely related species available in GenBank. ML bootstrap values (≥40 %) are indicated. The Finnish strain reported in this study is indicated in red. The scale bar indicates 0.005 expected changes per site per branch. The NCBI accession numbers of the strains used in the analyses are listed in the Supplementary Files.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-8637135/v1/122c82915c8acffcb4817e2f.png"},{"id":102747312,"identity":"407f3c1d-a4d9-44de-a450-b9655b9a4eef","added_by":"auto","created_at":"2026-02-16 09:04:30","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":197563,"visible":true,"origin":"","legend":"\u003cp\u003ePhylogenetic tree inferred using maximum likelihood analysis of an ITS dataset from \u003cem\u003eLecanosticta acicola \u003c/em\u003eand closely related species. \u003cem\u003ePhaeophleospora eugeniae\u003c/em\u003e was used as the outgroup. Maximum likelihood bootstrap values (≥ 20%) are shown. The Finnish strain reported in this study is indicated in red. The scale bar represents 0.02 expected substitutions per site. The NCBI accession numbers of the strains used in the analyses are listed in the Supplementary Files.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-8637135/v1/7c91073a13c4f49913af4b95.png"},{"id":103056406,"identity":"9aa54d71-bc0f-45eb-a631-2d6fcadaed27","added_by":"auto","created_at":"2026-02-20 09:09:23","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2206101,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8637135/v1/a38ee519-0c50-42c2-8dc4-376d3adc69fd.pdf"},{"id":102604786,"identity":"59c12784-b0a2-433c-b7af-7868b0dfde29","added_by":"auto","created_at":"2026-02-13 13:48:53","extension":"xlsx","order_by":7,"title":"","display":"","copyAsset":false,"role":"supplement","size":13062,"visible":true,"origin":"","legend":"","description":"","filename":"GenBankaccessionstrainsphylogenetics.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-8637135/v1/a292903bb13d82c3255d088c.xlsx"}],"financialInterests":"","formattedTitle":"First record of brown spot needle blight (BSNB) caused by Lecanosticta acicola on Pinus mugo in Finland","fulltext":[{"header":"Introduction","content":"\u003cp\u003eRecent evidence indicates that current environmental trends are increasing the risk of large-scale climate system instability (Ripple et al., \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Climate change is a key driver of emerging and invasive forest disturbances, particularly by favouring fungal pathogens. Rising temperatures facilitate the expansion of pathogen geographic ranges, allowing species previously restricted by cold climates to establish in new regions (Dudney et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Li et al., \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Singh et al., \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Terhonen et al., \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2025a\u003c/span\u003e). This process promotes the introduction of novel disease agents into forest ecosystems, where native host species often lack effective resistance (Barnes et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; George et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). In addition, warmer conditions, such as milder winters, enhance pathogen overwintering success and increase infection pressure (Hanso \u0026amp; Drenkhan, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Ma et al., \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Caballol et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Climatic variables, particularly temperature and precipitation, are therefore major determinants of the global distribution of phytopathogenic fungi (Větrovsk\u0026yacute; et al., \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Li et al., \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), and their diversity and invasion potential are expected to increase in forest ecosystems under future climate scenarios.\u003c/p\u003e \u003cp\u003e \u003cem\u003eLecanosticta acicola\u003c/em\u003e is the causal agent of brown spot needle blight (BSNB). Symptoms appear, as name indicates, brown spots with a yellow halo that encircle the needle (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea), that can lead to necrosis at the distal end (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb). In the necrotic tissue the fungus forms black stromata. Finally, \u003cem\u003eL. acicola\u003c/em\u003e produces oval, black fruiting bodies (acervuli-like) bearing conidia that emerge through the epidermis. The conidia are subhyaline to dark olive-green and thick-walled (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec). They have a rounded tip and a truncated base, vary in shape from fusiform to cylindrical, and range from straight to slightly curved (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec). Heavily infected pine trees often retain only the current year\u0026rsquo;s needles on twigs (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed). Repeated infections can cause extensive needle shedding and, in severe cases, the death of pine trees (van der Nest et al., \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe disease, BSNB, became widely recognized in the early 1900s after it caused severe damage to longleaf pine (\u003cem\u003ePinus palustris\u003c/em\u003e) forests in the southeastern United States (de Th\u0026uuml;men, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e1878\u003c/span\u003e; Siggers, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e1944\u003c/span\u003e; Sinclair \u0026amp; Lyon, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2005\u003c/span\u003e). Beginning in the 1990s, BSNB also emerged in many European countries (van der Nest et al., \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Laas et al. \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Tubby et al., \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). In Europe, \u003cem\u003eL. acicola\u003c/em\u003e is considered an invasive species, with evidence of multiple independent introduction events (Janoušek et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Laas et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Tubby et al., \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Human activity has likely played a significant role in its spread across the continent (Janoušek et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; van der Nest et al., \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). The pathogen has been recorded since the 2000s on several pine species (such as \u003cem\u003eP. nigra, P. uncinata, P. ponderosa, P. pumila\u003c/em\u003e and \u003cem\u003eP. halepensis)\u003c/em\u003e in 24 European countries (Tubby et al., \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). However, the most severe and repeated outbreaks have occurred on \u003cem\u003ePinus mugo\u003c/em\u003e (van der Nest et al., \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Tubby et al., \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cem\u003eLecanosticta acicola\u003c/em\u003e has also been confirmed on Scots pine (\u003cem\u003ePinus sylvestris\u003c/em\u003e) (Adamson et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Klaviņa et al., 2025). Distribution modelling suggests that \u003cem\u003eL. acicola\u003c/em\u003e is likely to become increasingly established in Europe\u0026mdash;including Finland\u0026mdash;under future climate scenarios (Ogris et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Given the economic, cultural, and ecological importance of Scots pine, \u003cem\u003eL. acicola\u003c/em\u003e should be considered a potential and emerging threat to Finnish pine-dominated forests. Young stands and nurseries are particularly vulnerable, which would affect forest regeneration success and facilitate the spread of the disease into new areas.\u003c/p\u003e \u003cp\u003eAttempts to detect \u003cem\u003eL. acicola\u003c/em\u003e in Finland have been made previously (Tubby et al., \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), but without success. Symptomatic needles of \u003cem\u003ePinus\u003c/em\u003e spp. have been tested at the Natural Resources Institute Finland, and in October 2025 \u003cem\u003eL. acicola\u003c/em\u003e was detected for the first time in Finland in symptomatic non-native \u003cem\u003eP. mugo\u003c/em\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Material and Methods","content":"\u003cp\u003eIn October 2025, needle cast of older needles and brown needle spots were observed on \u003cem\u003eP. mugo\u003c/em\u003e in southwest Finland (60\u0026deg;22'59.16''N, 23\u0026deg;7'59.16''E). The tree was growing as urban ornamental in front of a building (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed). Needles with brown spots and yellow halo were collected for analysis (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea). The needles were surface-sterilized with 70% EtOH, air-dried, and then surface-sterilized for 1 min in 2.4% NaOCl, followed by three rinses in DDW. Needles were cut into ~\u0026thinsp;1 cm pieces, placed on 2% MEA, and incubated at +\u0026thinsp;15\u0026deg;C in darkness for 3 weeks. All fast-growing fungi were discarded. Slowly growing black hyphae surrounded by white hyphae emerging from the brown spots (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ee) were subcultured, and the conidia were examined microscopically (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec). Representative strains are stored on MEA slants at 4\u0026deg;C at the Natural Resources Institute Finland (Luke).\u003c/p\u003e \u003cp\u003eMolecular identification based on the ITS region was performed following Terhonen (\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Briefly, DNA was isolated using the PrepMan\u0026trade; Ultra Sample Preparation Reagent (Applied Biosystems, Foster City, CA, USA) according to Linnakoski et al. (\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). The ITS1\u0026ndash;5.8S\u0026ndash;ITS2 region of rDNA was amplified using the primer pair ITS1-F (White et al., \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e1990\u003c/span\u003e) and ITS4 (Gardes \u0026amp; Bruns, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e1993\u003c/span\u003e). The PCR mixture contained DreamTaq Green Mix (2\u0026times;) (Thermo Scientific\u0026trade;), 200 \u0026micro;M dNTPs, 0.5 \u0026micro;M of each primer, and 1 \u0026micro;l of crude template DNA; the reaction volume was adjusted to 15 \u0026micro;l with autoclaved MQ H₂O. PCR conditions were: 94\u0026deg;C for 3 min; 30 cycles of 94\u0026deg;C for 30 s, 55\u0026deg;C for 1 min, 72\u0026deg;C for 1 min; and a final extension at 72\u0026deg;C for 10 min. PCR products were visualised under UV light on 1.5% agarose gel (Ethidium Bromide staining) and purified using the EXO-SAP protocol (Exonuclease I and Shrimp Alkaline Phosphatase; Thermo Fisher Scientific, Waltham, MA, USA) (Linnakoski et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2016\u003c/span\u003e) and sequenced using the ITS1 primer at Macrogen (Germany).\u003c/p\u003e \u003cp\u003eThe β-tubulin region was amplified using the primer pairs Btub2Fd and Btub4Rd (Woudenberg et al., \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). Polymerase chain reaction (PCR) was performed using the Phire Plant Direct PCR Master Mix (F160S, Thermo Scientific\u0026reg;, Thermo Fisher Scientific), following the manufacturer\u0026rsquo;s instructions. PCR cycling conditions were as follows: initial denaturation at 98\u0026deg;C for 30 s; 30 cycles of 98\u0026deg;C for 5 s, 60\u0026deg;C for 5 s, and 72\u0026deg;C for 5 s; followed by a final extension at 72\u0026deg;C for 1 min. PCR products were visualised under UV light on a 1\u0026ndash;1.2% agarose gel stained with DNA Stain G (SERVA Electrophoresis GmbH, Heidelberg, Germany). PCR products were purified using the Monarch\u0026reg; PCR \u0026amp; DNA Cleanup Kit (5 \u0026micro;g) (New England Biolabs, Ipswich, MA, USA) according to the manufacturer\u0026rsquo;s instructions and sent to Eurofins Genomics (Germany) for Sanger sequencing in both directions.\u003c/p\u003e \u003cp\u003eITS and β-tubulin sequences were analysed using MEGA12 (Kumar et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Sequence identity was verified by aligning the obtained sequences with reference sequences in the GenBank database via NCBI BLAST (Altschul et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e1990\u003c/span\u003e; Sayers et al., \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). The ITS (550 b) and β-tubulin (445 b) sequences were deposited in the European Nucleotide Archive (ENA) under accessions OZ373024 and OZ387206, respectively. The ITS and β-tubulin sequences, along with the corresponding BLAST results, are available at Zenodo (DOI: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.5281/zenodo.17951324\u003c/span\u003e\u003cspan address=\"10.5281/zenodo.17951324\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e).\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003ePhylogenetic analysis\u003c/h2\u003e \u003cp\u003eSequences were aligned using the MUSCLE algorithm (Edgar, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2004\u003c/span\u003e) implemented in Unipro UGENE v53.0 (Okonechnikov et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). The resulting alignment was inspected and manually refined where necessary. Phylogenetic placement of the fungal isolates was inferred using maximum likelihood (ML) analysis in raxmlGUI v2.0 (Edler et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), implementing RAxML with a GTR\u0026thinsp;+\u0026thinsp;Gamma\u0026thinsp;+\u0026thinsp;I nucleotide substitution model. ML analyses were performed in 10 independent runs, and branch support was assessed using thorough bootstrap analysis with 1,000 replicates. The resulting phylogenetic tree was visualised in FigTree v1.4.4 and subsequently edited using graphical softwares. Phylogenetic trees were constructed using a combination of the ITS and β-tubulin regions, as well as the ITS region alone. GenBank accession numbers for the strains used are provided in the Supplementary File.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eFour strains of \u003cem\u003eL. acicola\u003c/em\u003e were isolated from brown spots on still-living, surface-sterilized needles. Morphological identification was performed based on conidial characteristics (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed; EPPO Bulletin 2015), and species identity was confirmed for all four strains using ITS rDNA sequencing and β-tubulin (DOI: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.5281/zenodo.17951324\u003c/span\u003e\u003cspan address=\"10.5281/zenodo.17951324\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e). The ITS region showed a 100% identity (537/537 bp; 100% query coverage) with TYPE strain of \u003cem\u003eL. acicola\u003c/em\u003e (GenBank accession NR_120239.1), while the β-tubulin gene sequence exhibited a 100% identity (326/326 bp; 71% query coverage) with TYPE strain of \u003cem\u003eL. acicola\u003c/em\u003e (GenBank accession KC013008.1). Only reliable regions of the ITS and β-tubulin sequences were submitted to GenBank, and these were identical among all isolates. The phylogenetic analysis further confirmed the species as \u003cem\u003eL. acicola\u003c/em\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis study reports the first occurrence of brown spot needle blight (BSNB) in Finland. The causal agent, \u003cem\u003eL. acicola\u003c/em\u003e, has not previously been recorded in the country. Recent findings show that the pathogen can shift from exotic to native hosts, including Scots pine, and may establish in local pine populations (Adamson et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Klaviņa et al., 2025). Although the present detection concerns a non-native \u003cem\u003eP. mugo\u003c/em\u003e, the establishment of \u003cem\u003eL. acicola\u003c/em\u003e suggests that Finnish conditions may permit its survival and potential spread to native Scots pine (Adamson et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Ogris et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Klavina et al., 2025).\u003c/p\u003e \u003cp\u003eScots pine accounts for approximately 50% of the total growing stock volume in Finland (1,250\u0026nbsp;million m\u0026sup3;; Korhonen et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2024\u003c/span\u003e), and by the end of October 2025, the average stumpage price for pine logs was \u0026euro;155 (Natural Resources Institute Finland, statistical database). Beyond its economic role in the forest industry, Scots pine is also a culturally significant species, forming an iconic element of Finland\u0026rsquo;s forest landscapes. Ecologically, its importance is considerable: Finland hosts only around 30 native tree species, and Scots pine contributes substantially to forest structure, biodiversity, and ecosystem functioning.\u003c/p\u003e \u003cp\u003eIn Europe, several eradication attempts have been implemented to prevent the establishment and spread of \u003cem\u003eL. acicola\u003c/em\u003e (see case studies in Tubby et al., \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Despite eradication efforts, \u003cem\u003eL. acicola\u003c/em\u003e has spread from non-native pine hosts (Adamson et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2015\u003c/span\u003e) to native Scots pine eight years after its initial detection (Adamson et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2018\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eEPPO lists \u003cem\u003eL. acicola\u003c/em\u003e as an A2 pest (EPPO code SCIRAC), indicating that it is present in the EPPO region, but is recommended for regulation as a quarantine pest in member countries to limit its further spread (see PM1/002(34)). \u003cem\u003eLecanosticta acicola\u003c/em\u003e is classified as a Quality Plant Pest by the Finnish Food Authority so this pathogen must not be present in any plants sold in Finland, making \u003cem\u003eL. acicola\u003c/em\u003e a significant concern for seedling production and trade (see case study 3 in Tubby et al. (\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2023\u003c/span\u003e)). At the same time, future availability and effectiveness of control methods are uncertain. In Finland, three fungicidal active substances\u0026mdash;azoxystrobin (authorised until 02 August 2026), benzovindiflupyr (authorised until 2 August 2026), and prothioconazole (authorised until 15 August 2026)\u0026mdash;are currently approved for use in forest nurseries against needle cast diseases. However, first, it is unknown whether these substances are effective against \u003cem\u003eL. acicola\u003c/em\u003e; second, fungicidal active substances are continuously evaluated in the EU, and some may be withdrawn if they are not reapproved. Additionally, no compensation is provided for discarded seedlings for nursery producers (see case study 3 in Tubby et al., \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThere is an urgent need for research to ensure preparedness for the potential spread of \u003cem\u003eL. acicola\u003c/em\u003e, particularly to evaluate how effective integrated pest management (IPM) strategies in forest nurseries could prevent infections. When combined with tree breeding, such approaches may provide viable solutions to control and limit pathogen spread. Scots pine exhibits substantial genetic variation, with heritable traits differing among regions, enabling populations to adapt to local environmental conditions (Kujala et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Savolainen et al. \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Pyh\u0026auml;j\u0026auml;rvi et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Harnessing this genetic diversity in targeted breeding programs represents an opportunity to reduce any disease impacts. Accordingly, future research should focus on identifying the genetics and heritability underlying possible resistance, thereby enabling effective resistance breeding programs in pines (Fraser et al. 2015, Terhonen et al. \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2025b\u003c/span\u003e). Together with eradication measures and nursery-based IPM, these strategies could provide effective means to restrict the spread of the invasive pathogen \u003cem\u003eL. acicola\u003c/em\u003e in Finland.\u003c/p\u003e \u003cp\u003eOverall, tree health should be communicated more effectively to citizens, who can play a valuable role in helping researchers detect new threats (Terhonen et al. \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2025a\u003c/span\u003e). Keeping trees healthy requires combined efforts from policymakers, researchers, government, and the public.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eThe authors declare that there is no conflict of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported via Horizon Europe IA project Precilience (Grant Agreement 101157094) and Natural Resources Institute Finland (Luke). Milo\u0026scaron; Trifković was supported by the Specific University Research Fund of the Faculty of Forestry and Wood Technology, Mendel University in Brno (grant No LDF_VP_2019021). Linda Mutanen and Tuija Hyt\u0026ouml;nen are acknowledged for their help with the laboratory work.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAdamson, K., Drenkhan, R. and Hanso, M. 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In: Innis MA, Gelfand DH, Sninsky JJ, White TJ (eds) \u003cem\u003ePCR Protocols: A Guide to Methods and Applications\u003c/em\u003e. Academic Press, pp 315\u0026ndash;322. https://doi.org/10.1016/B978-0-12-372180-8.50042-1\u003c/li\u003e\n\u003cli\u003eWoudenberg JHC, Aveskamp MM, De Gruyter J, Spiers AG, Crous PW (2009) Multiple \u003cem\u003eDidymella\u003c/em\u003e teleomorphs are linked to the \u003cem\u003ePhoma clematidina\u003c/em\u003e morphotype. \u003cem\u003ePersoonia\u003c/em\u003e 22: 56\u0026ndash;62. https://doi.org/10.3767/003158509X427808\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"journal-of-plant-diseases-and-protection","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jpdp","sideBox":"Learn more about [Journal of Plant Diseases and Protection](https://www.springer.com/journal/41348)","snPcode":"41348","submissionUrl":"https://www.editorialmanager.com/jpdp","title":"Journal of Plant Diseases and Protection","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"climate change, emerging, invasive pathogen, Mycosphaerella dearnessii, Scots pine","lastPublishedDoi":"10.21203/rs.3.rs-8637135/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8637135/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eClimate change has already been acknowledged to have destabilizing effects on tree health. In addition to increased abiotic disturbances, trees are increasingly negatively impacted by the emergence of fungal pathogens. \u003cem\u003eLecanosticta acicola\u003c/em\u003e, the causal agent of brown spot needle blight (BSNB), affects pines and is considered invasive in Europe. In October 2025, typical symptoms of \u003cem\u003eL. acicola\u003c/em\u003e, brown circumferential lesions with a yellow halo, were observed on an urban tree, \u003cem\u003ePinus mugo\u003c/em\u003e. The pathogen was isolated from surface-sterilized needles, and morphological and molecular identification confirmed it as \u003cem\u003eL. acicola\u003c/em\u003e. Here, we report the first observation of the invasive pathogen \u003cem\u003eL. acicola\u003c/em\u003e on the non-native host \u003cem\u003eP. mugo\u003c/em\u003e in Finland. \u003cem\u003eLecanosticta acicola\u003c/em\u003e is classified as a Quality Plant Pest by the Finnish Food Authority and as no suitable plant protection methods are currently available in Finland, this finding is of particular significance. The detection of this pathogen highlights a potential threat to forestry and emphasizes the need for preventive strategies to limit its spread, including eradication, resistance breeding and improved integrated pest management (IPM) practices in nurseries.\u003c/p\u003e","manuscriptTitle":"First record of brown spot needle blight (BSNB) caused by Lecanosticta acicola on Pinus mugo in Finland","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-13 13:48:40","doi":"10.21203/rs.3.rs-8637135/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Minor revisions","date":"2026-03-27T11:49:36+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2026-02-10T12:26:55+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-02-10T09:08:44+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Journal of Plant Diseases and Protection","date":"2026-01-21T21:19:53+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-01-21T13:16:35+00:00","index":"","fulltext":""},{"type":"submitted","content":"Journal of Plant Diseases and Protection","date":"2026-01-19T03:51:57+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"journal-of-plant-diseases-and-protection","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jpdp","sideBox":"Learn more about [Journal of Plant Diseases and Protection](https://www.springer.com/journal/41348)","snPcode":"41348","submissionUrl":"https://www.editorialmanager.com/jpdp","title":"Journal of Plant Diseases and Protection","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"e599e79d-bfc8-4363-aff1-a673c3855889","owner":[],"postedDate":"February 13th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-05-16T17:55:51+00:00","versionOfRecord":[],"versionCreatedAt":"2026-02-13 13:48:40","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8637135","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8637135","identity":"rs-8637135","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}