The increasing threat to European forests from the invasive foliar pine pathogen, Lecanosticta acicola.

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 Pathogen reports from the literature, and new/ unpublished survey data were combined into an open-access geo-database (http://www.portalofforestpathology.com), and used to visualise the pathogen's range, infer its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.

First Report of 'Candidatus Phytoplasma mali,' the Causal Agent of Apple Proliferation Disease, in Apple Trees in Finland.

Based on an earlier survey of putative psyllid vectors of apple proliferation (AP), carried out in 2009 and 2010, Cacopsylla picta (Förster) populations infected with 'Candidatus Phytoplasma mali' were detected in at least two commercial apple (Malus domestica Borkh.) orchards in southern Finland (1). To establish the presence of 'Ca. P. mali' in apple trees, a survey was conducted in 17 commercial apple orchards in August 2012. Phytosanitary inspectors tracked the source of the 'Ca. P. mali' by collecting 33 leaf samples from trees showing probable symptoms. Typical symptoms, including elongated stipules and witches' broom, were rare. Total DNA was extracted from leaves using a DNeasy Plant Mini Kit (Qiagen, Hilden, Germany) and screened for 'Ca. P. mali' with real-time PCR (2) and the commercial Apple Proliferation Group - complete PCR reaction kit (Loewe Biochemica GmbH, Sauerlach, Germany). Two samples tested positive and results were confirmed with TaqMan PCR and conventional PCR assays and DNA sequencing in the Food and Environment Research Agency (Fera), in the United Kingdom. One positive sample was taken from an orchard in Lohja, southern Finland, where high 'Ca. P. mali' incidence in overwintered C. picta was observed in 2010 (1). 'Ca. P. mali' was found in a >40-year-old 'Red Melba' tree with witches' broom but without elongated stipule symptoms. The other positive sample was collected from an orchard in the Aland Islands, where the infected 'Lobo' tree showed symptoms of elongated stipules. This orchard was not monitored for AP vectors. No small fruit symptoms were noted by inspectors or growers in either of the orchards. The positive samples were further analyzed for subtypes using PCR/RFLP and primers AP13/AP10 (3). The amplicons (776 bp) were sequenced and digested with HincII and BspHI (New England BioLabs Inc., Ipswich, MA) following manufacturer's instructions. Both samples proved to be apple proliferation subtypes AT-1 on the basis of RFLP and the sequenced 776-bp region. Sequences of the 776-bp amplicon of the Lohja and Aland isolates showed 100% and 99% identity, respectively, with sequences of apple proliferation isolates (accession nos. L22217.1 and CU469464.1) in GenBank. Both suspected psyllid vectors of 'Ca. P. mali' C. picta and C. melanoneura (Förster) occur in Finland, but their distribution, abundance, and transmission specificity is inadequately documented. The next step to evaluate the risk of spread of apple proliferation in commercial orchards is an extensive survey of the occurrence of Cacopsylla species infected with 'Ca. P. mali'. References: (1) A. Lemmetty et al. B. Insectol. 64:257, 2011. (2) P. Nikolic et al. Mol. Cell. Probes. 24:303, 2010. (3) W. Jarausch et al. Mol. Cell. Probes 14:17, 2000.

First Report of Hop stunt viroid in Greenhouse Cucumber in Finland.

In July 2009, the occurrence of pale yellow, bottle-shaped greenhouse cucumber (Cucumis sativus L.) fruits was reported by a horticultural adviser from Kannus in western Finland. The grower had observed the first symptoms in greenhouse cucumber cv. Rapides in May. The most distinctive symptoms were found in fruits, but also flowers were crumpled. Symptoms had spread along plant rows. Estimated yield loss by the grower was 2 to 3%. Fruit and flower symptoms were typical of cucumber pale fruit disease (3) caused by a strain of Hop stunt viroid (HSVd) (2). The original samples were collected by a phytosanitary inspector and the farmer from approximately 10 symptomatic plants growing in the same greenhouse. Testing two samples, one a cucumber leaf and the other a cucumber fruit, by return-polyacrylamide gel electrophoresis gave clear electrophoretic bands at the same position. However, the position of the bands differed slightly from the positive control (Potato spindle tuber viroid) and two other pospiviroids tested on the same gel, indicating the presence of a different viroid with a shorter length than those from the genus Pospiviroid. This observation of size combined with symptoms on cucumber gave a strong indication of the presence of a viroid, likely to be HSVd. RNA was extracted from two subsamples of fruit and leaf samples with a RNeasy Plant Mini Kit (Qiagen, Hilden, Germany). Extracted RNA was examined with primer pair HSVdF1/R1 designed to detect HSVd from citrus (1). The PCR reactions were performed using a reverse transcription-PCR protocol developed for Pospiviroids (4). Both fruit and leaf samples gave a PCR amplicon of the same size. Sequencing of the amplicon of approximately 300 bp revealed 99% similarity with 11 GenBank citrus isolates of HSVd and 98% similarity with two cucumber isolates of HSVd (Accession Nos. X07405 and X00524) On the basis of these results, the viroid of these cucumber plants was identified as HSVd. To our knowledge, this is the first finding of this viroid in Finland. Although we could determine the causal agent, we could not find the origin of the infection. The seedling plants had been grown in the same greenhouse where the infection was detected. Even though HSVd is not known to be seed transmitted (3) the other production places that had used the same seed lot were inspected and found to be free of the viroid. Very strict phytosanitary measures were taken to eradicate the infection. Since the viroid is easily sap transmissible, there is a certain risk of spreading of HSVd via human action, e.g., visitors, staff, and the use of common packing facilities. References: (1) L. Bernard and N. Duran-Vila. Mol. Cell. Probes 20:105, 2006. (2) T. Sano et al. Nucleic Acids Res. 12:3427, 1984. (3) H. J. M. van Dorst and D. Peters. Neth. J. Plant Pathol. 80:85, 1974. (4) J. Th. J. Verhoeven et al. Eur. J. Plant Pathol. 110:823, 2004.