RESUMO
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 Pathogen reports from the literature, and new/ unpublished survey data were combined into an open-access geo-database (http://www.portalofforestpathology.com), and used to visualise the pathogen's range, infer its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.
RESUMO
In many European countries, the anamorphic Chalara fraxinea Kowalski (teleomorph Hymenoscyphus albidus [Roberge ex Desm.] Phillips; 1-3) is responsible for a severe and rapidly spreading dieback of common ash (Fraxinus excelsior L.) since it was first reported in Poland. Recently, this disease was added to the EPPO Alert List and the NAPPO Phytosanitary Alert System. Symptomatic trees were observed in a 1.8-ha ash-maple forest in northeastern Italy (Fusine, UD; 46°30'N, 13°37'E; 782 m above sea level) along the Italo-Slovenian border in July 2009. Symptoms were found on approximately 10% of mature common ash and 70% of seedlings. Main symptoms were shoot, twig, and branch dieback, wilting, and bark cankers (1). Fungal fruiting bodies were not found on or near the canker surface. Furthermore, longitudinal and radial sections through the cankers revealed gray-to-brown xylem discoloration. One symptomatic 3-year-old plant was randomly selected and from the necrotic margin of one canker previously surface-sterilized with 3% sodium hypochlorite and rinsed, four 2-mm-wide chips were placed on malt extract agar (MEA) and incubated at 21 ± 1°C in the dark. Among a variety of microorganisms, after 19 days, slow-growing colonies (mean radius of 12 mm) appeared that were effuse, cottony, and often fulvous brown but sometimes dull white with occasional gray-to-dark gray patches. The purified isolate was then transferred to the same medium at 4 ± 1°C in the dark, and after 11 days, hyaline-to-dark gray phialides were observed producing numerous conidia in slimy droplets and sometimes in chains. Phialophores measured 8.6 to 21.0 (15.1) µm long (n = 20), 4.2 to 13.4 (8.8) × 3.6 to 5.5 (4.7) µm at the base, and 5.2 to 8.7 (6.5) × 2.5 to 3.1 (2.8) µm at the collarette; conidia measured 2.8 to 4.2 (3.4) × 1.9 to 2.5 (2.2) µm (n = 40); and first formed conidia measured 5.5 to 6.5 (5.9) × 1.8 to 2.5 (2.1) µm (n = 20). These morphological characteristics matched Kowalski's (1) description of C. fraxinea. In August of 2009, the fungal isolate was used to test pathogenicity with current year shoots of 25 6-year-old (150 to 210 cm high) asymptomatic common ash trees under quarantine conditions (Slovenian Forestry Institute's experimental plots). For every plant, the bark of the main shoot (10 to 13 mm in diameter) was wounded with a 6-mm-diameter cork borer. Twenty saplings were inoculated with one 6-mm-diameter mycelial plug obtained from the margin of a 26-day-old culture (MEA), while five saplings were inoculated with sterile MEA plugs. All wounds were sealed with Parafilm and aluminum foil. After 28 days, all plants inoculated with the C. fraxinea showed bark lesions (2 to 39 mm long, mean 7 mm) and wood discoloration (6 to 85 mm long, mean 22 mm) from which the pathogen was reisolated. These symptoms were absent from controls and the pathogen was never reisolated. To our knowledge, this is the first report of C. fraxinea in Italy. Investigations on its presence in all Fraxinus species naturally growing in the investigated area and in the nearest regions are in progress. The obtained isolate is preserved in both Padova and Ljubljana herbaria as CFIT01. References: (1) T. Kowalski. For. Pathol. 36:264, 2006. (2) T. Kowalski and O. Holdenrieder. For. Pathol. 39:1, 2009. (3) T. Kowalski and O. Holdenrieder. For. Pathol. 39:304, 2009.
