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Special Issue "Joint IUFRO 7.02.02 “Foliage, shoot and stem diseases of forest trees” and 7.03.04 “Diseases and insects in forest nurseries” Working Parties Meeting"

A special issue of Forests (ISSN 1999-4907).

Deadline for manuscript submissions: closed (1 October 2015)

Special Issue Editors

Guest Editor
Prof. Dr. Jan Stenlid

Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences, P.O. Box 7026, SE-75007 Uppsala, Sweden
Website | E-Mail
Phone: +46 18 671 807
Guest Editor
Dr. Jonas Oliva

Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences, P.O. Box 7026, SE-75007 Uppsala, Sweden
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Guest Editor
Dr. Audrius Menkis

Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences, P.O. Box 7026, SE-75007 Uppsala, Sweden
Website | E-Mail
Phone: +46 18 672 729

Special Issue Information

Dear Colleagues,

While forest threats are acting on a global scale, new and invasive diseases have been reported at an increasing rate, and are predicted to be even more frequent in the future. Both natural and managed forest ecosystems are affected. Forest nurseries are also among the most vulnerable environments affected by pathogens. To reduce losses, relevant responses to such diseases should be associated with proper understandings of biological concepts concerning pathogens and the elaboration of countermeasures for their control. The joint IUFRO meeting aims to share and discuss recent research experiences that are fundamental for addressing practical problems, as forest diseases affect ecosystems across national borders.

Prof. Dr. Jan Stenlid
Dr. Jonas Oliva
Dr. Audrius Menkis
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Forests is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • new and invasive diseases; foliage, shoot and stem diseases
  • forest nurseries; pathogens control
  • diseases and insects
  • biological concepts of pathogens

Published Papers (19 papers)

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Research

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Open AccessArticle Metabarcoding of Bacteria Associated with the Acute Oak Decline Syndrome in England
Forests 2016, 7(5), 95; https://doi.org/10.3390/f7050095
Received: 30 October 2015 / Revised: 27 January 2016 / Accepted: 19 April 2016 / Published: 26 April 2016
Cited by 8 | PDF Full-text (3296 KB) | HTML Full-text | XML Full-text
Abstract
Outbreaks of acute oak decline (AOD) have been documented in England from 2006. Both species of native oaks (Quercus robur and Quercus petraea) are affected. To complement isolation efforts for identification of putative causative biotic agents and increase our understanding of [...] Read more.
Outbreaks of acute oak decline (AOD) have been documented in England from 2006. Both species of native oaks (Quercus robur and Quercus petraea) are affected. To complement isolation efforts for identification of putative causative biotic agents and increase our understanding of bacteria associated with oak tissue, five sites in England were chosen for this study. Samples of outer bark, inner bark, sapwood and heartwood were taken from healthy oak and trees with symptoms at varying stages of the syndrome. Furthermore, larval galleries attributed to infestation with Agrilus biguttatus were included. After DNA extraction and amplification of the V3–V5 fragment of the bacterial 16S rRNA genes by pyrosequencing, the dataset was analyzed to identify patterns in bacterial communities in oak tissue samples with and without AOD symptoms at each site. The composition of bacterial communities differed greatly according to the site from which the samples were obtained. Within each site, the composition of the bacteria associated with symptomatic tissue varied between advanced stages of the syndrome and healthy tissue. Key players in healthy and symptomatic tissue were identified and included members of the Gammaproteobacteria related to Pseudomonas sp. or Brenneria goodwinii and members of the Firmicutes. Full article
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Open AccessFeature PaperArticle High-Throughput Sequencing Shows High Fungal Diversity and Community Segregation in the Rhizospheres of Container-Grown Conifer Seedlings
Forests 2016, 7(2), 44; https://doi.org/10.3390/f7020044
Received: 25 November 2015 / Revised: 1 February 2016 / Accepted: 4 February 2016 / Published: 17 February 2016
Cited by 7 | PDF Full-text (1978 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Forest nurseries in Sweden produce ca. 360 million seedlings of Pinus sylvestris L. and Picea abies (L.) Karst. annually. Fungi represent the largest microbial component in rhizospheres and may significantly affect health and, consequently, quality of the seedlings. The aim of this study [...] Read more.
Forest nurseries in Sweden produce ca. 360 million seedlings of Pinus sylvestris L. and Picea abies (L.) Karst. annually. Fungi represent the largest microbial component in rhizospheres and may significantly affect health and, consequently, quality of the seedlings. The aim of this study was to assess fungi focusing on pathogens in roots and the sphagnum peat growth substrate of healthy-looking P. sylvestris and P. abies seedlings from nine forest nurseries situated in northern, central and southern regions of Sweden. We hypothesized that nursery stock and the growth substrate can provide a venue for dissemination of fungal diseases. In each nursery and for each tree species, 100 seedlings with the growth substrate were collected during the dormant period. DNA was isolated from parts of root systems and from samples of the growth substrate, amplified using internal transcribed spacer of rDNA as a marker and 454-sequenced. Clustering at 98.5% similarity of 169,844 high-quality sequences resulted in 619 non-singleton fungal taxa. Although results showed that management practices in forest nurseries generally give a healthy stock, latent establishment of pathogenic fungi in both roots and the growth substrate supported the hypothesis. Furthermore, seedling roots and the growth substrate were inhabited by distinct communities of fungi, and lifestyles of these fungi largely determined community segregation into particular ecological niche. Full article
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Open AccessArticle Development of Ash Dieback in South-Eastern Germany and the Increasing Occurrence of Secondary Pathogens
Forests 2016, 7(2), 41; https://doi.org/10.3390/f7020041
Received: 1 October 2015 / Revised: 18 January 2016 / Accepted: 3 February 2016 / Published: 15 February 2016
Cited by 9 | PDF Full-text (3008 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Since its first identification in Poland in 2006, the ascomycete Hymenoscyphus fraxineus has caused massive dieback of Fraxinus excelsior in the countries of eastern, northern and central Europe. This work shows the development, expansion, and severity of the disease in south-eastern Germany for [...] Read more.
Since its first identification in Poland in 2006, the ascomycete Hymenoscyphus fraxineus has caused massive dieback of Fraxinus excelsior in the countries of eastern, northern and central Europe. This work shows the development, expansion, and severity of the disease in south-eastern Germany for a period of four years, starting in 2010. Differences between habitats, as well as age classes have been captured. The presence and the amount of potentially resistant trees were proven over the years, to determine how high the resistance level might be. Typical disease symptoms are the wilting of leaves, necrotic lesions in the bark and reddish discolorations of branches and stems. In addition, stem necroses also appear by infection with species of Armillaria. Therefore, special attention has been given to Armillaria species in affected ash stands but also to other secondary pathogens, like ash bark beetles. It is shown that breeding galleries of Hylesinus fraxini are only found in trees that have recently died and thus Hylesinus fraxini is still acting as a secondary opportunistic pathogen. In contrast, Armillaria spp. can be considered as serious pathogens of weakened ash trees. In different ash stands, typical symptoms of infection can be found. A relationship between stem base necrotic lesions and vitality was examined. It is shown that necrotic lesions severely contribute to accelerating the mortality of ash trees. In addition to the high infection pressure by H. fraxineus, the high inoculum of Armillaria in the soil facilitates further infections and, thus, likewise endangers the survival of potentially resistant trees. In the following years, forest conversion and seed harvest in affected ash stands will have to be urgently considered to avoid tree gaps on a large scale. Furthermore, infection assays of potentially resistant trees with ensuing breeding programmes should be initially started for the conservation of this ecologically and economically important tree species. Full article
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Open AccessArticle Synthesis and New Observations on Needle Pathogens of Larch in Northern Finland
Forests 2016, 7(1), 25; https://doi.org/10.3390/f7010025
Received: 16 November 2015 / Revised: 12 January 2016 / Accepted: 13 January 2016 / Published: 18 January 2016
Cited by 3 | PDF Full-text (4519 KB) | HTML Full-text | XML Full-text
Abstract
Needle pathogens of larch (Larix spp.) in the Nordic countries are under-studied. Their incidence in Finland tends to be low and local, and this may be a function of enemy release, since species of larch were introduced to the region. Here, the [...] Read more.
Needle pathogens of larch (Larix spp.) in the Nordic countries are under-studied. Their incidence in Finland tends to be low and local, and this may be a function of enemy release, since species of larch were introduced to the region. Here, the ecology and incidence of larch needle pathogens and the abiotic factors that also affect larch in northern Finland are reviewed. Field observations and related laboratory analyses during the past 35 years have mainly been obtained near the Kivalo Research Area within the Arctic Circle, Finnish Lapland. The relatively recent introduction of Hypodermella laricis is a primary focus. This pathogen is not only new to Nordic countries, but can cause severe outbreaks, defoliation and crown-thinning in the canopies of all ages of most planted larch species worldwide. Symptoms of H. laricis clearly differ from those of Mycosphaerella laricina; the latter has affected Larix sibirica at high latitudes for decades. The effects of Meria laricis, Lophodermium laricinum, various rust fungi, and wind and frost are also discussed. Full article
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Open AccessArticle Quantifying the Impacts of Systemic Acquired Resistance to Pitch Canker on Monterey Pine Growth Rate and Hyperspectral Reflectance
Forests 2016, 7(1), 20; https://doi.org/10.3390/f7010020
Received: 1 October 2015 / Revised: 22 December 2015 / Accepted: 31 December 2015 / Published: 12 January 2016
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Abstract
Pitch canker, caused by Fusarium circinatum, is a disease affecting Monterey pine (Pinus radiata) and many other pine species throughout the world. The impact of pitch canker on Pinus radiata may be limited by systemic acquired resistance (SAR), a phenomenon that [...] Read more.
Pitch canker, caused by Fusarium circinatum, is a disease affecting Monterey pine (Pinus radiata) and many other pine species throughout the world. The impact of pitch canker on Pinus radiata may be limited by systemic acquired resistance (SAR), a phenomenon that elevates resistance to a pathogen after initial challenge by that pathogen or another microorganism. Allocation of resources to defense, as a consequence of SAR, is presumed to reduce resources available to support growth and reproduction, but specific fitness consequences associated with SAR in P. radiata have not been measured. To quantify impacts of SAR on growth rate, a 2 × 2 factorial experiment was established in which trees were either primed for SAR or unprimed, with half the trees in each of those two groups being inoculated with the pitch canker pathogen and the other half not inoculated. Priming for SAR was accomplished by inoculating one branch with F. circinatum and removing inoculated branches prior to subsequent challenge inoculations (= disease treatments). Disease treatments included three inoculations that were removed for measurement of lesion length, and three additional inoculations that remained on the tree as a representation of persistent disease. Control trees were mock inoculated with water. Main effects of priming and disease did not result in significant effects on growth rate. Based on hyperspectral canopy reflectance data, diseased trees were associated with higher difference vegetation index values and biomass. The absence of a negative impact on growth rate associated with SAR suggests that induction of resistance may have utility as a tool for management of pitch canker in plantations. Full article
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Open AccessArticle Assessments of Population Structure, Diversity, and Phylogeography of the Swiss Needle Cast Fungus (Phaeocryptopus gaeumannii) in the U.S. Pacific Northwest
Forests 2016, 7(1), 14; https://doi.org/10.3390/f7010014
Received: 2 October 2015 / Revised: 10 December 2015 / Accepted: 17 December 2015 / Published: 6 January 2016
Cited by 3 | PDF Full-text (2868 KB) | HTML Full-text | XML Full-text
Abstract
Swiss needle cast (SNC) is a foliar disease of Douglas-fir (Pseudotsuga menziesii) caused by Phaeocryptopus gaeumannii (Rohde) Petrak. This fungus is endemic to western North America, where it has historically had little impact in native forests. However, increasing disease severity in [...] Read more.
Swiss needle cast (SNC) is a foliar disease of Douglas-fir (Pseudotsuga menziesii) caused by Phaeocryptopus gaeumannii (Rohde) Petrak. This fungus is endemic to western North America, where it has historically had little impact in native forests. However, increasing disease severity in western Oregon since the 1990s has prompted renewed interest in P. gaeumannii and SNC. For this study, we analyze multilocus microsatellite genotypes from 482 single-spore isolates from 68 trees across 14 sites in the western Coast Range of Oregon and southwestern Washington. This study assesses genotypic variation and genetic structure at several levels of population hierarchy. Despite the observation that most of the genetic variation occurred within subpopulations, our analyses detected significant differentiation at all hierarchical levels. Clustering among the 482 isolates based on genetic distance clearly supports the existence of two previously described cryptic lineages of P. gaeumannii in the western United States. The two lineages occur in varying proportions along latitudinal and longitudinal gradients in western Oregon and Washington, suggesting a relationship between climate and phylogeography. Sites near Tillamook, Oregon, where SNC is most severe, consist of sympatric subpopulations in which the two lineages comprise roughly equal proportions. Full article
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Open AccessArticle Delphinella Shoot Blight on Abies lasiocarpa Provenances in Norway
Forests 2016, 7(1), 7; https://doi.org/10.3390/f7010007
Received: 6 November 2015 / Revised: 10 December 2015 / Accepted: 17 December 2015 / Published: 25 December 2015
Cited by 3 | PDF Full-text (4719 KB) | HTML Full-text | XML Full-text
Abstract
Delphinella shoot blight (Delphinella abietis) attacks true firs (Abies spp.) in Europe and North America. Especially subalpine fir (A. lasiocarpa), one of the main Christmas tree species in Norway, is prone to the disease. The fungus kills current [...] Read more.
Delphinella shoot blight (Delphinella abietis) attacks true firs (Abies spp.) in Europe and North America. Especially subalpine fir (A. lasiocarpa), one of the main Christmas tree species in Norway, is prone to the disease. The fungus kills current year needles, and in severe cases entire shoots. Dead needles become covered with black fruiting bodies, both pycnidia and pseudothecia. Delphinella shoot blight has mainly been a problem in humid, coastal regions in the northwestern part of Southern Norway, but, probably due to higher precipitation in inland regions during recent years, heavy attacks were found in 2011 in a field trial with 76 provenances of subalpine fir in Southeastern Norway. However, the amount of precipitation seemed less important once the disease had established in the field. Significant differences in susceptibility between provenances were observed. In general, the more bluish the foliage was, the healthier the trees appeared. The analysis of provenance means indicated that, at least for the southern range, the disease ratings were correlated with foliage color. This study also includes isolation, identification, a pathogenicity test, a seed test and electron microscopy of the wax layer on the needles. The fungus was identified based on the morphology of spores and by sequencing the Internal Transcribed Spacer (ITS) regions of the ribosomal DNA. Koch’s postulates were fulfilled. The fungus was found present on newly harvested seeds and may therefore spread via international seed trade. When comparing the wax layers on green and blue needles, those of the latter were significantly thicker, a factor that may be involved in disease resistance. Full article
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Open AccessArticle Detection of Airborne Inoculum of Hymenoscyphus fraxineus and H. albidus during Seasonal Fluctuations Associated with Absence of Apothecia
Forests 2016, 7(1), 1; https://doi.org/10.3390/f7010001
Received: 1 October 2015 / Revised: 30 November 2015 / Accepted: 9 December 2015 / Published: 22 December 2015
Cited by 12 | PDF Full-text (3693 KB) | HTML Full-text | XML Full-text
Abstract
Hymenoscyphus fraxineus is an invasive fungal species causing the most serious disease of ashes (Fraxinus spp.) in Europe—ash dieback. The biology of this fungus is not totally elucidated, neither its relation to the saprophytic species Hymenoscyphus albidus, native in Europe. Our [...] Read more.
Hymenoscyphus fraxineus is an invasive fungal species causing the most serious disease of ashes (Fraxinus spp.) in Europe—ash dieback. The biology of this fungus is not totally elucidated, neither its relation to the saprophytic species Hymenoscyphus albidus, native in Europe. Our study is focused on the description of seasonal spore dispersal of both fungi and its relation to meteorological conditions, which is needed for more precise and effective control of the disease. For this experiment one long time infected mixed forest in the SE Czech Republic was chosen. A seven-day automatic volumetric spore trap and a weather station were installed to continuously sample the aerospora from April to October 2014. In seven periods a rotating arm spore trap was also used to obtain 48-h air samples to compare the efficiency of these two types of air samplers. Air samples were evaluated solely by qPCR with a very low detection limit. Results show co-occurrence of inoculum of both fungi throughout the entire sampling period with peak levels in August. The origin of the inoculum sampled in the periods without apothecia is discussed. Air-inoculum occurrence of both fungi is significantly correlated with each other, suggesting their coexistence in this forest. Full article
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Open AccessArticle Extent and Severity of Caliciopsis Canker in New England, USA: An Emerging Disease of Eastern White Pine (Pinus strobus L.)
Forests 2015, 6(11), 4360-4373; https://doi.org/10.3390/f6114360
Received: 6 October 2015 / Revised: 19 November 2015 / Accepted: 19 November 2015 / Published: 24 November 2015
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Abstract
Caliciopsis canker is an emerging problem in Pinus growing regions of Eastern North America. The fungal disease caused by Caliciopsis pinea is associated with overstocked stands and poor sites, but few quantitative data are available. The objective of this study, therefore, was to [...] Read more.
Caliciopsis canker is an emerging problem in Pinus growing regions of Eastern North America. The fungal disease caused by Caliciopsis pinea is associated with overstocked stands and poor sites, but few quantitative data are available. The objective of this study, therefore, was to assess the extent and severity of Caliciopsis canker and to explore environmental variables associated with disease to identify areas at risk of damage. During 2014, 58 sites across New England with >75% P. strobus basal area in public lands were surveyed. Most sites (72%) had Caliciopsis canker signs or symptoms. Caliciopsis pinea was successfully identified with molecular techniques. In sites with Caliciopsis canker, 36% of the mature pines were symptomatic. Pole sized and suppressed trees were more likely to be damaged than larger trees with dominant crown positions (p < 0.05). Pinus strobus density for sites with Caliciopsis canker was 311 trees/ha (mean P. strobus stand diameter = 40 cm) compared to 220 trees/ha (mean white pine stand diameter = 43 cm) for sites without Caliciopsis canker (p = 0.1). Caliciopsis canker symptoms tended to appear more frequently in stands with excessively drained, coarse textured soils derived from glacial outwash (86%) or stands with poorly drained soils and low fertility (78%) than in stands with well drained, more fertile soils (59%) (p = 0.1). The severity of symptoms varied among soil groups and was greater for excessively drained, nutrient poor soils than for well-drained, more fertile soils (p = 0.027). Full article
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Open AccessArticle Phylogenetic Relationships among Species of Phellinus sensu stricto, Cause of White Trunk Rot of Hardwoods, from Northern North America
Forests 2015, 6(11), 4191-4211; https://doi.org/10.3390/f6114191
Received: 30 September 2015 / Accepted: 4 November 2015 / Published: 18 November 2015
Cited by 3 | PDF Full-text (1680 KB) | HTML Full-text | XML Full-text
Abstract
Species in Phellinus s.s. are some of the most important wood-decaying fungal pathogens in northern temperate forests, yet data on species incidence in North America remains limited. Therefore, phylogenetic analyses were performed using four loci (ITS, nLSU, tef1 and rpb2) with isolates [...] Read more.
Species in Phellinus s.s. are some of the most important wood-decaying fungal pathogens in northern temperate forests, yet data on species incidence in North America remains limited. Therefore, phylogenetic analyses were performed using four loci (ITS, nLSU, tef1 and rpb2) with isolates representing 13 species. Results of phylogenetic analyses using maximum likelihood and Bayesian inference revealed that eight species of Phellinus s.s. occur in North America, and include: P. alni, P. arctostaphyli, P. betulinus, P. lundellii, P. nigricans, P. tremulae and two undescribed species, P. NA1 and P. NA2. Meanwhile, P. tuberculosus, P. igniarius s.s., P. populicola, P. laevigatus s.s. and P. orienticus were not detected and appear restricted to Europe and/or Asia. The tef1 dataset outperformed all other loci used and was able to discriminate among all 13 of the currently known Phellinus s.s. species with significant statistical support. The internal transcribed spacer (ITS) region performed well but a high level of intraspecific variation could lead to inflated taxa recognition. Phellinus alni exhibited the broadest host range, as demonstrated previously, and appears to be the most common species in northern hardwood (Acer-Betula-Fagus), northern floodplain (Fraxinus-Populus-Ulmus) and coastal alder (Alnus) forests of North America. Full article
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Open AccessArticle Designing Strategies for Epidemic Control in a Tree Nursery: the Case of Ash Dieback in the UK
Forests 2015, 6(11), 4135-4145; https://doi.org/10.3390/f6114135
Received: 25 September 2015 / Revised: 6 November 2015 / Accepted: 6 November 2015 / Published: 18 November 2015
Cited by 4 | PDF Full-text (586 KB) | HTML Full-text | XML Full-text
Abstract
Ash dieback is a fungal disease (causal agent Hymenoscyphus fraxineus) infecting Common ash (Fraxinus excelsior) throughout temperate Europe. The disease was first discovered in the UK in 2012 in a nursery in Southern England, in plants which had been imported [...] Read more.
Ash dieback is a fungal disease (causal agent Hymenoscyphus fraxineus) infecting Common ash (Fraxinus excelsior) throughout temperate Europe. The disease was first discovered in the UK in 2012 in a nursery in Southern England, in plants which had been imported from the Netherlands. After sampling other recently planted sites across England, more infected trees were found. Tree trade from outside and across the UK may have facilitated the spread of invasive diseases which threaten the sustainability of forestry business, ecological niches and amenity landscapes. Detecting a disease in a nursery at an early stage and knowing how likely it is for the disease to have spread further in the plant trade network, can help control an epidemic. Here, we test two simple sampling rules that 1) inform monitoring strategies to detect a disease at an early stage, and 2) inform the decision of tracking forward the disease after its detection. We apply these expressions to the case of ash dieback in the UK and test them in different scenarios after disease introduction. Our results are useful to inform policy makers’ decisions on monitoring for the control and spread of tree diseases through the nursery trade. Full article
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Open AccessArticle Characterization of Fungal Pathogens Associated with White Pine Needle Damage (WPND) in Northeastern North America
Forests 2015, 6(11), 4088-4104; https://doi.org/10.3390/f6114088
Received: 9 September 2015 / Revised: 4 November 2015 / Accepted: 6 November 2015 / Published: 12 November 2015
Cited by 14 | PDF Full-text (1557 KB) | HTML Full-text | XML Full-text
Abstract
Eastern white pine is a crucial ecological and economic component of forests in the northern USA and eastern Canada, and is now facing an emerging problem in white pine needle damage (WPND). It is still unclear whether WPND results from one, or the [...] Read more.
Eastern white pine is a crucial ecological and economic component of forests in the northern USA and eastern Canada, and is now facing an emerging problem in white pine needle damage (WPND). It is still unclear whether WPND results from one, or the combination of several fungal pathogens. Therefore, the first objective of this study was to characterize the fungi associated with WPND in the northeastern United States and document the damage being done to mature eastern white pine as a result of repeated defoliation. To date, 22 species of fungi, either cultured from diseased pine needles or formed fruiting bodies on pine needles were identified based on morphology and sequence data. Lecanosticta acicola and a putative new species of Septorioides were the species most frequently recovered from diseased needles, in addition to needle cast fungi Lophophacidium dooksii and Bifusella linearis, two obligate fungal pathogens that were frequently observed on pine needles in the northeast, but have not been known to cause excessive defoliation of eastern white pine. A second objective was to monitor yearly the health of 63 pairs of healthy and unhealthy trees in eight affected locations throughout New England. Since 2012, affected trees are increasingly and repeatedly chlorotic and defoliated every year. Trees that were initially healthy are now exhibiting symptoms. While L. acicola appears to be the primary pathogen causing WPND, several other common needle pathogens are being more frequently observed and the role of climate change may be important in the disease ecology of WPND. These defoliation events, while once a sporadic occurrence, have now become more frequent as observed in continued crown deterioration of eastern white pine in long-term monitoring plots followed during the course of this three-year study. Full article
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Open AccessCommunication Genetic Variability and Phylogeny of European mountain ash ringspot-associated virus RNA3 and RNA4
Forests 2015, 6(11), 4072-4087; https://doi.org/10.3390/f6114072
Received: 31 August 2015 / Accepted: 29 October 2015 / Published: 11 November 2015
Cited by 2 | PDF Full-text (840 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The European mountain ash ringspot-associated virus (EMARaV) is a multipartite RNA virus of negative polarity. It infects Sorbus aucuparia (common name—rowan) trees throughout their whole distribution area in North and Central Europe. It causes mottling, chlorotic ringspots and decline of the whole plant. [...] Read more.
The European mountain ash ringspot-associated virus (EMARaV) is a multipartite RNA virus of negative polarity. It infects Sorbus aucuparia (common name—rowan) trees throughout their whole distribution area in North and Central Europe. It causes mottling, chlorotic ringspots and decline of the whole plant. Infected rowans are serious virus sources for rowans and other potential hosts. EMARaV incidence and population structure was investigated in Germany, Finland, Sweden, Scotland, and Norway. Overall, EMARaV variants from 42 rowan trees distributed in 20 different locations were studied with regard to the genetic variability of the p3- and p4-coding genome region, as well as the 5′ and 3′ untranslated regions (UTR) of RNA3. In six of the 42 analyzed samples we found much higher sequence diversities than previously reported at the amino acid level in RNA3 encoded p3 protein sequences as well as at the nucleotide level on the 5′ and 3′ UTR. The other 36 EMARaV variants confirmed the assumed conservation of the nucleocapsid protein coding region. In contrast, the p4-coding genome region showed a high conservation of both nucleotide and amino acid sequences. Both EMARaV proteins were under strong purifying selection pressure, probably acting to maintain the functional integrity of the p3 and p4 proteins. Full article
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Open AccessArticle Two-Year Survival of Gremmeniella abietina Conidia Collected on Branches Left on the Ground after Pine Harvesting
Forests 2015, 6(11), 4055-4058; https://doi.org/10.3390/f6114055
Received: 29 September 2015 / Revised: 2 November 2015 / Accepted: 3 November 2015 / Published: 9 November 2015
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Abstract
In 1972, it was reported that viable ascospores and conidia of Gremmeniella abietina, North American race, were present on dead branches up to 10 months after they were killed. In Sweden, the survival period of conidia of G. abietina, European race, [...] Read more.
In 1972, it was reported that viable ascospores and conidia of Gremmeniella abietina, North American race, were present on dead branches up to 10 months after they were killed. In Sweden, the survival period of conidia of G. abietina, European race, was reported to be over 18 months. We investigated the viability of conidia produced by G. abietina, European race, over a 2-year period in eastern Canada. Infected branches with pycnidia were left on the ground in June 2006. Branches were sampled every month during three growing seasons. Conidia germination was tested monthly and showed a very high rate of germination (76%–98%) from July 2006 to August 2007. Very few pycnidia were detected in the fall of 2007 and in May 2008. In June and July 2008, no pycnidia could be observed, the shoots being in an advanced stage of decomposition. In light of these observations, it is recommended to delay pine plantation until after two growing seasons following harvesting of diseased pine trees. Full article
Open AccessArticle Impact of a Mountain Pine Beetle Outbreak on Young Lodgepole Pine Stands in Central British Columbia
Forests 2015, 6(10), 3483-3500; https://doi.org/10.3390/f6103483
Received: 25 June 2015 / Revised: 18 September 2015 / Accepted: 28 September 2015 / Published: 30 September 2015
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Abstract
The current mountain pine beetle (MPB) (Dendroctonous ponderosae Hopkins) epidemic has severely affected pine forests of Western Canada and killed millions of hectares of lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) forest. Generally, MPB attack larger and older [...] Read more.
The current mountain pine beetle (MPB) (Dendroctonous ponderosae Hopkins) epidemic has severely affected pine forests of Western Canada and killed millions of hectares of lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) forest. Generally, MPB attack larger and older (diameter > 20 cm or >60 years of age) trees, but the current epidemic extends this limit with attacks on even younger and smaller trees. The study’s aim was to investigate the extent of MPB attack in young pine stands and its possible impact on stand dynamics. Although MPB attacks were observed in trees as small as 7.5 cm diameter at breast height (DBH) and as young as 13 years old, the degree of MPB attack (percent stems ha−1) increased with increasing tree diameter and age class (13–20, 21–40, 41–60, and 61–80 years old) (6.4%, 49.4%, 62.6%, and 69.5% attack, respectively, by age class) which is greater than that reported from previous epidemics for stands of this age. The mean density of surviving residual structure varied widely among age classes and ecological subzones. Depending on age class, 65% to 77% of the attacked stands could contribute to mid-term timber supply. The surviving residual structure of young stands offers an opportunity to mitigate the effects of MPB-attack on future timber supply, increase age class diversity, and enhance ecological resilience in younger stands. Full article
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Open AccessArticle Impact of Seed Transmission on the Infection and Development of Pitch Canker Disease in Pinus radiata
Forests 2015, 6(9), 3353-3368; https://doi.org/10.3390/f6093353
Received: 25 August 2015 / Accepted: 17 September 2015 / Published: 23 September 2015
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Abstract
The aim of this study was to determine the impact of seed inoculum on subsequent disease development in nurseries, specifically studying incidence of seed infection, transmission rate of seed to seedlings, and rate of disease development from the primary inoculum source. Transmission rate [...] Read more.
The aim of this study was to determine the impact of seed inoculum on subsequent disease development in nurseries, specifically studying incidence of seed infection, transmission rate of seed to seedlings, and rate of disease development from the primary inoculum source. Transmission rate of Fusarium circinatum (F. circinatum) from symptomatic trees of Pinus radiata (P. radiata) to seed was 0.73%, being the fungus mainly on the coat. Seed infection incidence was positively correlated with tree disease severity. Seeds also become contaminated with F. circinatum during storage, where high relative humidity had a great effect regardless of temperature. Transmission rates from seeds to symptomatic seedlings measured at 48 days after seed inoculation with 104 and 106 was 28% and 80%, respectively. Seedlings showed symptoms of wilting and dieback, and eventually died within the total duration of this study (475 days). By this time, there were two remaining symptomless seedlings (1% of the total). F. circinatum was recovered from each of them, demonstrating its persistence in seedlings. Fungus populations in roots were estimated between 105 and 107 cfu/g in symptomatic plants for both inoculum doses and up to 104 cfu/g in asymptomatic plants. Disease infection rate was similar in post-emergence damping-off (up two months growing) and for established seedlings (up to eight months) after seeds were inoculated with 104 spores/mL. Full article
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Open AccessArticle Effect of Chitosan on Disease Control and Growth of Scots Pine (Pinus sylvestris L.) in a Forest Nursery
Forests 2015, 6(9), 3165-3176; https://doi.org/10.3390/f6093165
Received: 26 June 2015 / Revised: 3 August 2015 / Accepted: 18 August 2015 / Published: 11 September 2015
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Abstract
Chitosan has become a promising biological agent for disease control and plant growth promotion. The objective of this study was to assess the effects of chitosan, applied as an active ingredient of Beta-chikol (Poli-Farm, Łowicz, Poland), to control damping-off and Lophodermium needle cast [...] Read more.
Chitosan has become a promising biological agent for disease control and plant growth promotion. The objective of this study was to assess the effects of chitosan, applied as an active ingredient of Beta-chikol (Poli-Farm, Łowicz, Poland), to control damping-off and Lophodermium needle cast on Scots pine seedlings growing in field conditions. Beta-chikol was used for seed treatment and as a foliar spray at recommended rates and concentrations. For each experimental variant (chitosan, fungicides, unprotected), inventories of seedlings were performed, after germination and again after six weeks. In the aboveground parts of seedlings, the concentration of endogenous salicylic acid was determined by HPLC. At the end of the growing season, seedling growth parameters were determined. Beta-chikol used as foliar spray limited infection by the damping-off fungi but was ineffective when used as a seed treatment. Lophodermium needle cast was not observed during the study period. After the application of Beta-chikol, the concentration of salicylic acid did not increase. The application of Beta-chikol enhanced all growth parameters under investigation. Our results indicate the possibility of using chitosan in the form of Beta-chikol to stimulate plant growth and protect pine seedlings against parasitic damping-off in forest nurseries. Full article
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Open AccessArticle Molecular Identification of Phytoplasmas Infecting Diseased Pine Trees in the UNESCO-Protected Curonian Spit of Lithuania
Forests 2015, 6(7), 2469-2483; https://doi.org/10.3390/f6072469
Received: 16 June 2015 / Revised: 9 July 2015 / Accepted: 10 July 2015 / Published: 17 July 2015
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Abstract
Although mainly known as pathogens that affect angiosperms, phytoplasmas have recently been detected in diseased coniferous plants. In 2008–2014, we observed, in the Curonian Spit of Western Lithuania and in forests of Southern Lithuania (Varena district), diseased trees of Scots pine (Pinus [...] Read more.
Although mainly known as pathogens that affect angiosperms, phytoplasmas have recently been detected in diseased coniferous plants. In 2008–2014, we observed, in the Curonian Spit of Western Lithuania and in forests of Southern Lithuania (Varena district), diseased trees of Scots pine (Pinus sylvestris) and mountain pine (Pinus mugo) with unusual symptoms similar to those caused by phytoplasmas. Diseased trees exhibited excessive branching, dwarfed reddish or yellow needles, dried shoots and ball-like structures. restriction fragment length polymorphism (RFLP) and nucleotide sequence analysis of 16S rRNA gene fragments revealed that individual trees were infected by Candidatus (Ca.) Phytoplasma pini-related strains (members of phytoplasma subgroup 16SrXXI-A) or by Ca. Phytoplasma asteris-related strains (subgroup 16SrI-A). Of the nearly 300 trees that were sampled, 80% were infected by phytoplasma. Ninety-eight percent of the positive samples were identified as Ca. Phytoplasma pini-related strains. Strains belonging to subgroup 16SrI-A were identified from only few trees. Use of an additional molecular marker, secA, supported the findings. This study provides evidence of large-scale infection of Pinus by Ca. Phytoplasma pini in Lithuania, and it reveals that this phytoplasma is more widespread geographically than previously appreciated. This is also the first report of phytoplasma subgroup 16SrI-A in pine trees. Full article
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Open AccessReview Scientometrics of Forest Health and Tree Diseases: An Overview
Forests 2016, 7(1), 17; https://doi.org/10.3390/f7010017
Received: 28 September 2015 / Revised: 28 December 2015 / Accepted: 4 January 2016 / Published: 8 January 2016
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Abstract
Maintaining forest health is a worldwide challenge due to emerging tree diseases, shifts in climate conditions and other global change stressors. Research on forest health is thus accumulating rapidly, but there has been little use of scientometric approaches in forest pathology and dendrology. [...] Read more.
Maintaining forest health is a worldwide challenge due to emerging tree diseases, shifts in climate conditions and other global change stressors. Research on forest health is thus accumulating rapidly, but there has been little use of scientometric approaches in forest pathology and dendrology. Scientometrics is the quantitative study of trends in the scientific literature. As with all tools, scientometrics needs to be used carefully (e.g., by checking findings in multiple databases) and its results must be interpreted with caution. In this overview, we provide some examples of studies of patterns in the scientific literature related to forest health and tree pathogens. Whilst research on ash dieback has increased rapidly over the last years, papers mentioning the Waldsterben have become rare in the literature. As with human health and diseases, but in contrast to plant health and diseases, there are consistently more publications mentioning “tree health” than “tree disease,” possibly a consequence of the often holistic nature of forest pathology. Scientometric tools can help balance research attention towards understudied emerging risks to forest trees, as well as identify temporal trends in public interest in forests and their health. Full article
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