•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.
European forests are threatened by increasing numbers of invasive pests and pathogens. Over the past century, Lecanosticta acicola, a foliar pathogen predominantly of Pinus spp., has expanded its range globally, and is increasing in impact. Lecanosticta acicola causes brown spot needle blight, resulting in premature defoliation, reduced growth, and mortality in some hosts. Originating from southern regions of North American, it devastated forests in the USA’s southern states in the early twentieth century, and in 1942 was discovered in Spain.
Derived from Euphresco project ‘Brownspotrisk,’ this study aimed to establish the current distribution of Lecanosticta species, and assess the risks of L. acicola to European forests. Pathogen reports from the literature, and new/ unpublished survey data were combined into an open-access geo-database (http://www.portalofforestpathology.com), and used to visualise the pathogen’s range, infer its climatic tolerance, and update its host range. Lecanosticta species have now been recorded in 44 countries, mostly in the northern hemisphere. The type species, L. acicola, has increased its range in recent years, and is present in 24 out of the 26 European countries where data were available. Other species of Lecanosticta are largely restricted to Mexico and Central America, and recently Colombia.
The geo-database records demonstrate that L. acicola tolerates a wide range of climates across the northern hemisphere, and indicate its potential to colonise Pinus spp. forests across large swathes of the Europe. Preliminary analyses suggest L. acicola could affect 62% of global Pinus species area by the end of this century, under climate change predictions.
Although its host range appears slightly narrower than the similar Dothistroma species, Lecanosticta species were recorded on 70 host taxa, mostly Pinus spp., but including, Cedrus and Picea spp. Twenty-three, including species of critical ecological, environmental and economic significance in Europe, are highly susceptible to L. acicola, suffering heavy defoliation and sometimes mortality. Variation in apparent susceptibility between reports could reflect variation between regions in the hosts’ genetic make-up, but could also reflect the significant variation in L. acicola populations and lineages found across Europe. This study served to highlight significant gaps in our understanding of the pathogen’s behaviour.
Lecanosticta acicola has recently been downgraded from an A1 quarantine pest to a regulated non quarantine pathogen, and is now widely distributed across Europe. With a need to consider disease management, this study also explored global BSNB strategies, and used Case Studies to summarise the tactics employed to date in Europe.
Summary
Lecanosticta acicola causes brown spot needle blight (BSNB) of Pinus species. The pathogen occurs mostly in the Northern Hemisphere but has also been reported in Central America and Colombia. ...BSNB can lead to stunted growth and tree mortality, and has resulted in severe damage to pine plantations in the past. There have been increasingly frequent new reports of this pathogen in Europe and in North America during the course of the past 10 years. This is despite the fact that quarantine practices and eradication protocols are in place to prevent its spread.
Taxonomy
Kingdom Fungi; Phylum Ascomycota; Subphylum Pezizomycotina; Class Dothideomycetes; Subclass Dothideomycetidae; Order Capniodales; Family Mycosphaerellaceae; Genus Lecanosticta.
Host range and distribution
Lecanosticta spp. occur on various Pinus species and are found in North America, Central America, South America (Colombia), Europe as well as Asia.
Disease symptoms
Small yellow irregular spots appear on the infected pine needles that become brown over time. They can be surrounded by a yellow halo. These characteristic brown spots develop to form narrow brown bands that result in needle death from the tips down to the point of infection. Needles are prematurely shed, leaving bare branches with tufts of new needles at the branch tips. Infection is usually most severe in the lower parts of the trees and progresses upwards into the canopies.
Useful websites
The EPPO global database providing information on L. acicola (https://gd.eppo.int/taxon/SCIRAC)
Reference genome of L. acicola available on GenBank (https://www.ncbi.nlm.nih.gov/genome/?term=Lecanosticta+acicola)
JGI Gold Genome database information sheet of L. acicola sequenced genome (https://gold.jgi.doe.gov/organism?xml:id=Go0047147)
•Synthesis of the impact of current and future climate change on Pinus strobus and eastern white pine ecosystem.•Impact of climate change on foliar, canker and root rot pathogens of P. ...strobus.•Synopsis of White Pine Needle Damage (WPND) over the last decade.•Comparison of WPND with other globally important pine pathogens.
Climate model predictions for the northeastern U.S. forecast a warmer and wetter climate, which favors the survival, reproduction and dispersal of foliar diseases of eastern white pine, collectively called White Pine Needle Damage (WPND). Foliar diseases cause defoliation of white pine, leading to growth reductions, canopy dieback and predisposing trees to other pathogens and insects. This situation is very similar to other conifer foliar diseases, such as Dothistroma needle blight (DNB) in British Columbia and Swiss needle cast (SNC) in Oregon, where the climate is also becoming warmer and wetter. The purpose of this review is to summarize recent WPND findings of the impact climate change, particularly increased spring precipitation and annual warming has on the emergence of this disease complex. These findings will then be related to what is currently known about climatic factors affecting DNB and SNC and their role as native foliar pathogens affecting their natural forest ecosystems. We also discuss other eastern white pine diseases such as blister rust, cankers, and root rots in relation to climate change.
For northern Europe Lecanosticta acicola is an emerging pine needle pathogen. This study gives a first look into the population genetics of the pathogen in Estonia, the first population documented in ...that region. The main aim of this study was to investigate the genetic diversity and population structure of the pathogen in this new region for the fungus. For this purpose, 104 isolates from 2010 to 2017 were analysed with 11 microsatellite and mating type markers. The stand where the pathogen's jump from an exotic host to the native Scots pine was recorded was also involved in this analysis. The analysis revealed low genetic diversity and a high number of clones that indicated L. acicola is an invasive species in northern Europe. Results suggest that several separate introductions have taken place and anthropogenic activity has apparently affected the spread of the pathogen. Clonal reproduction is dominating and although sexual reproduction is possible, it probably takes place infrequently.
Brown spot needle blight, a disease of pine trees caused by the pathogenic fungus Lecanosticta acicola, has been known in Lithuania since 2009 and in Poland since 2014, but data on the distribution ...and population genetics of this needle pathogen were lacking. In order to investigate the genetic diversity, population structure and reproductive mode of L. acicola, 93 isolates were isolated from Pinus mugo needles in 2017–2019 and analysed using 11 microsatellite and two mating‐type markers. This study revealed 47 unique multilocus haplotypes among all investigated isolates; two genetically distinct populations of L. acicola (LIT‐E and LIT‐W) were identified in Lithuania and one population (POL‐N) in the coastal region of northern Poland. The most genetically diverse population was the LIT‐E population occurring in the eastern continental part of Lithuania, followed by the LIT‐W population spreading along the western Baltic Sea coast. All populations in both countries are characterized by low genetic diversity and contain clones, with the northern Polish population having the lowest mean genetic diversity and the greatest clonal fraction. Both mating types are present in the Lithuanian populations, demonstrating that sexual reproduction is possible, whereas only one mating type is present in the Polish population. However, the sexual stage (teleomorph) has not yet been found on infected needles, and asexual reproduction predominates. High gene flow from the eastern Lithuanian population to the northern Poland population was found, suggesting that the Polish coastal population may have been introduced from the central part of Lithuania and did not spread naturally along the Baltic Sea coast from the western Lithuanian population.
Three genetically different L. acicula populations were identified. High gene flow from the eastern Lithuanian to the northern Polish population suggested that the latter may have been introduced from the central part of Lithuania.
Brown spot needle blight (BSNB), caused by
Lecanosticta acicola
(Thüm.) Syd., is an emerging forest disease of
Pinus
species originating from North America and introduced to Europe and Asia. Severity ...and spread of the disease has increased in the last two decades in North America and Europe as a response to climate change. No modeling work on spread, severity, climatic suitability, or potential distribution has been done for this important emerging pathogen. This study utilizes a global dataset of 2,970 independent observations of
L. acicola
presence and absence from the geodatabase, together with
Pinus
spp. distribution data and 44 independent climatic and environmental variables. The objectives were to (1) identify which bioclimatic and environmental variables are most influential in the distribution of
L. acicola
; (2) compare four modeling approaches to determine which modeling method best fits the data; (3) examine the realized distribution of the pathogen under climatic conditions in the reference period (1971–2000); and (4) predict the potential future global distribution of the pathogen under various climate change scenarios. These objectives were achieved using a species distribution modeling. Four modeling approaches were tested: regression-based model, individual classification trees, bagging with three different base learners, and random forest. Altogether, eight models were developed. An ensemble of the three best models was used to make predictions for the potential distribution of
L. acicola
: bagging with random tree, bagging with logistic model trees, and random forest. Performance of the model ensemble was very good, with high precision (0.87) and very high AUC (0.94). The potential distribution of
L. acicola
was computed for five global climate models (GCM) and three combined pathways of Shared Socioeconomic Pathway (SSP) and Representative Concentration Pathway (SSP-RCP): SSP1-RCP2.6, SSP2-RCP4.5, and SSP5-RCP8.5. The results of the five GCMs were averaged on combined SSP-RCP (median) per 30-year period. Eight of 44 studied factors determined as most important in explaining
L. acicola
distribution were included in the models: mean diurnal temperature range, mean temperature of wettest quarter, precipitation of warmest quarter, precipitation seasonality, moisture in upper portion of soil column of wettest quarter, surface downwelling longwave radiation of driest quarter, surface downwelling shortwave radiation of warmest quarter and elevation. The actual distribution of
L. acicola
in the reference period 1971–2000 covered 5.9% of
Pinus
spp. area globally. However, the model ensemble predicted potential distribution of
L. acicola
to cover an average of 58.2% of
Pinus
species global cover in the reference period. Different climate change scenarios (five GCMs, three SSP-RCPs) showed a positive trend in possible range expansion of
L. acicola
for the period 1971–2100. The average model predictions toward the end of the century showed the potential distribution of
L. acicola
rising to 62.2, 61.9, 60.3% of
Pinus
spp. area for SSP1-RCP2.6, SSP2-RCP4.5, SSP5-RCP8.5, respectively. However, the 95% confidence interval encompassed 35.7–82.3% of global
Pinus
spp. area in the period 1971–2000 and 33.6–85.8% in the period 2071–2100. It was found that SSP-RCPs had a little effect on variability of BSNB potential distribution (60.3–62.2% in the period 2071–2100 for medium prediction). In contrast, GCMs had vast impact on the potential distribution of
L. acicola
(33.6–85.8% of global pines area). The maps of potential distribution of BSNB will assist forest managers in considering the risk of BSNB. The results will allow practitioners and policymakers to focus surveillance methods and implement appropriate management plans.
Brown spot needle blight (BSNB), a disease of pine trees caused by the fungus Lecanosticta acicola, has been known in Slovenia since 2008 and in Croatia since 1975. Recent outbreaks in Slovenia ...prompted this study to compare L. acicola populations in these two neighbouring European countries. Sixty‐nine isolates collected from three pine species (Pinus mugo, P. halepensis and P. nigra) were used to determine the phylogenetic relationships, genetic structure, and reproductive strategy of the pathogen. EF1‐α sequences showed that Slovenian and Croatian isolates share a common ancestry with individuals from central and northern Europe. Population structure analysis revealed four distinct population clusters of L. acicola in these two countries, generally corresponding to their respective geographic location and host. An unequal ratio of mating types and a low overall genetic diversity in the population indicated a strong influence of asexual reproduction. Although some of the oldest recorded European occurrences of BSNB are from Croatia, this study provided no evidence that the population studied in Croatia was the source of the sampled outbreaks in Slovenia. Recent outbreaks of L. acicola in Slovenia are most likely due to introductions from other, yet to be identified, sources.
In recent years, there has been an apparent Europe-wide emerging presence of brown spot needle blight, a disease of pine species caused by the fungus Lecanosticta acicola. In this study, we report ...the first well-documented occurrences of the pathogen in Slovakia, identified molecularly using species-specific primers and based on sequencing of the ITS region and TEF1 gene. Among the material collected from 84 locations within the country, L. acicola was present in 17 samples from 13 different locations, mainly distributed in urban environments. Four pine species were identified as hosts, among which, Pinus nigra and P. mugo were found to be the most frequently infected. Analysis of the mating type genes of 24 isolates obtained from two localities revealed the presence of a single mating type in Slovakia. All analyzed ITS sequences of the Slovak isolates were found to be uniform. However, although analysis of the TEF1 gene indicated that all Slovak isolates could be grouped into a single lineage, we detected nucleotide polymorphisms suggestive of a certain degree of genetic diversification within central European populations of the fungus.
Brown spot needle blight, caused by Lecanosticta acicola, is a serious disease of pines worldwide and has become of great concern in Europe over the last decade, with significantly increased ...outbreaks in pine forests. We examined native and non‐native Pinaceae taxa (four Cedrus and 24 Pinus) in the Atatürk Arboretum, Istanbul, Turkey, for the presence of L. acicola. Needles were sampled from 37 trees at least twice between March 2017 and July 2018. Symptomatic occurrence of the disease was confirmed by isolations, followed by molecular identification via sequencing of the ITS region. Lecanosticta acicola was isolated from symptomatic needles of 10 trees from seven host taxa (Cedrus and six Pinus). Molecular diagnostics of isolates confirmed the identification of L. acicola on Cedrus libani, Pinus sylvestris, P. nigra subsp. nigra, P. nigra subsp. laricio, P. nigra subsp. pallasiana, P. nigra subsp. pallasiana var. fastigiata and P. nigra subsp. pallasiana var. pallasiana f. şeneriana in the arboretum.
This paper is the first report of L. acicola on C. libani and also the first report of the pathogen infecting a genus other than a Pinus spp. under natural conditions. Additionally, it is also the first report of L. acicola occurring in Turkey. The pathogen was clearly able to cause severe damage on native Turkish Pinus taxa, including P. sylvestris and P. nigra subsp. pallasiana, and endangered endemic forms of the host in Turkey.
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