- Summary of Invasiveness
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Distribution Table
- History of Introduction and Spread
- Risk of Introduction
- Habitat List
- Hosts/Species Affected
- Host Plants and Other Plants Affected
- Growth Stages
- List of Symptoms/Signs
- Biology and Ecology
- Means of Movement and Dispersal
- Pathway Causes
- Pathway Vectors
- Plant Trade
- Impact Summary
- Economic Impact
- Environmental Impact
- Social Impact
- Risk and Impact Factors
- Detection and Inspection
- Similarities to Other Species/Conditions
- Prevention and Control
- Gaps in Knowledge/Research Needs
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Puccinia buxi Sowerby 1809
Other Scientific Names
- Dasyspora buxi Arthur 1906
- Dicaeoma buxi (Sowerby) Gray 1821
- Micropuccinia buxi (Arthur) Arthur & H.S. Jacks. 1921
- Puccinia buxi DC. 1815
- Trailia buxi (Arthur) Syd. 1922
International Common Names
- English: Boxwood rust
Summary of InvasivenessTop of page
P. buxi is an autoecious microcyclic rust, completing its life cycle with two spore forms on one host. It is native to parts of Europe and Asia. An introduction to the USA, is evidence that it can be invasive with respect to other temperate countries, particularly because its hosts in the genus Buxus are often propagated vegetatively and may carry latent infections. Boxwoods have long been popular as ornamentals, therefore the rust’s current absence from North America and temperate regions of the southern hemisphere is puzzling; in the earliest introductions of the host, the pathogen would probably have been ignored or overlooked. Conditions of boxwood cultivation may discourage the rust’s growth and survival.
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Fungi
- Phylum: Basidiomycota
- Subphylum: Pucciniomycotina
- Class: Pucciniomycetes
- Order: Pucciniales
- Family: Pucciniaceae
- Genus: Puccinia
- Species: Puccinia buxi
Notes on Taxonomy and NomenclatureTop of page
This species is frequently cited as Puccinia buxi DC., but DeCandolle’s name is an illegitimate homonym of Sowerby’s binomial; Arthur’s binomial is treated as a new name (nomen novum).
DescriptionTop of page
Spermogonia, aecia and uredinia absent. Telia amphigenous, on indefinite spots, scattered or confluent, hemispherical, pulvinate, compact, erumpent, dark chestnut-brown. Teliospores oblong to clavate, rounded above, apex not thickened, rounded or attenuate below, 55-90 x 20-35 µm, up to 100 µm long, walls 2.0-2.5 µm thick, brown, upper cell with apical germ pore, lower cell with superior germ pore; pedicels hyaline, persistent, very long, up to 160 µm.
DistributionTop of page
P. buxi has been reported from Europe, North Africa, Iran, Japan, and China (Dennis, 1986). Occurrence in the islands of the Azores, Madeira, and the Ryukyus of Japan (Dennis, 1986) are presumably the result of introductions. Specimens have been collected from other parts of the range of the primary host, Buxus sempervirens (boxwood) (BPI, 2009).
Distribution TableTop of page
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.
|Continent/Country/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Reference||Notes|
|-Sichuan||Restricted distribution||Zhang et al., 1997||Daba Mountains|
|Iran||Present||BPI, US National Fungus Collections; Dennis, 1986|
|Japan||Present||Present based on regional distribution.|
|-Kyushu||Present, few occurrences|
|-Ryukyu Archipelago||Present||Dennis, 1986|
|Turkey||Present||Göbelez, 1963; Huseyin, 2005|
|USA||Present||Present based on regional distribution.|
|-Georgia||Present||BPI, US National Fungus Collections||2004|
|-Pennsylvania||Eradicated||2006||Introduced||Invasive||NAPPO, 2006||One location|
|Belgium||Present||BPI, US National Fungus Collections||1883|
|France||Widespread||Native||Not invasive||BPI, US National Fungus Collections; Liou, 1929; Durrieu, 2001|
|Germany||Present||BPI, US National Fungus Collections; Braun, 1982|
|Ireland||Present||BPI, US National Fungus Collections||1933|
|Italy||Present||Not invasive||BPI, US National Fungus Collections||1876, 1882, 1889|
|Portugal||Present||Gonzalez Fragoso, 1918|
|-Azores||Present||Gjærum and Sunding, 1986|
|-Madeira||Present, few occurrences||BPI, US National Fungus Collections; Gjærum and Sunding, 1986|
|Russian Federation||Present||Present based on regional distribution.|
|-Southern Russia||Present||BPI, US National Fungus Collections||Near Chosta in Caucasus Moutains. 1982|
|Slovenia||Present||Hauptman, 2008||In arboretum|
|Spain||Present||Native||Gonzalez Fragoso, 1918; Llorens i Villagrassa I, 1984|
|Switzerland||Present||BPI, US National Fungus Collections||1850, 1900, 1927|
|UK||Widespread||Grove, 1913; Foister, 1961; Dennis, 1986; Dennis, 1995|
History of Introduction and SpreadTop of page
In the summer of 2005, a nursery in Pennsylvania, USA received a shipment of boxwood (Buxus sempervirens) cuttings from various locations in Greece (NAPPO, 2006). Rooted cuttings were found to be infected with P. buxi the next spring. The infected plants were destroyed by autoclaving, and another shipment to an American nursery was quarantined.
IntroductionsTop of page
Risk of IntroductionTop of page
As the infection can be asymptomatic during the usual growing season, infected plant material or plants can be collected or grown and then transported across borders and oceans. Obviously infected material coming from various European countries to the USA also has been intercepted by the phytosanitary authorities (BPI, 2009). Boxwood (Buxus sempervirens) has long been a popular ornamental plant, thus it is surprising that introduction in earlier times has not resulted in establishment of this pathogen in the USA and other countries in temperate regions outside Europe. The usual conditions of boxwood cultivation and care may prevent the rust from surviving and proliferating (Durrieu, 2001), but the biology of the fungus is not known well enough to explain its low rate of spread.
Habitat ListTop of page
|Terrestrial – Managed||Managed forests, plantations and orchards||Present, no further details||Natural|
|Terrestrial ‑ Natural / Semi-natural||Natural forests||Present, no further details||Natural|
Hosts/Species AffectedTop of page
The rust has been reported from Buxus sempervirens (boxwood) and Buxus microphylla (littleleaf boxwood), commonly grown ornamentals, as well as from the Asian species, Buxus sinica (Chinese boxwood), a cold-hardy species from Korea (Batdorf, 1995).
Host Plants and Other Plants AffectedTop of page
Growth StagesTop of page Vegetative growing stage
SymptomsTop of page
List of Symptoms/SignsTop of page
|Leaves / abnormal colours|
|Leaves / abnormal leaf fall|
|Leaves / fungal growth|
|Leaves / leaves rolled or folded|
|Stems / dieback|
Biology and EcologyTop of page
P. buxi is an autoecious microcyclic rust, completing its life cycle on one host. Teliospores develop in the leaves through autumn and winter, emerging through the epidermis in winter or spring. They are not shed, but remain on the leaf and germinate without dormancy (Wilson and Henderson, 1966). The basidiospores produced then infect the new leaves (Grove, 1913). The teliospores have been reported to fall apart easily into their two cells (Grove, 1913), but the possible role of this character in dissemination of the fungus has not been examined.
ClimateTop of page
|Cf - Warm temperate climate, wet all year||Preferred||Warm average temp. > 10°C, Cold average temp. > 0°C, wet all year|
|Cs - Warm temperate climate with dry summer||Preferred||Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers|
Means of Movement and DispersalTop of page
Natural Dispersal (Non-Biotic)
In the summer of 2005, a nursery in Pennsylvania, USA received a shipment of boxwood (Buxus sempervirens) cuttings from various locations in Greece (NAPPO, 2006). Rooted cuttings in the nursery then developed telia of P. buxi in spring 2006.
Preece (2000) observed telia of the rust in England on cuttings in floral bouquets imported from southern Europe.
Pathway CausesTop of page
Pathway VectorsTop of page
Plant TradeTop of page
|Plant parts liable to carry the pest in trade/transport||Pest stages||Borne internally||Borne externally||Visibility of pest or symptoms|
|Leaves||hyphae; spores||Pest or symptoms not visible to the naked eye but usually visible under light microscope|
|Plant parts not known to carry the pest in trade/transport|
|Fruits (inc. pods)|
|Growing medium accompanying plants|
|Stems (above ground)/Shoots/Trunks/Branches|
|True seeds (inc. grain)|
Impact SummaryTop of page
Economic ImpactTop of page
Any losses due to this fungus are likely to result from restriction on exports or imports of Buxus plants or plant material, or from the destruction of infected imported planting material by nurseries or quarantine authorities.
Environmental ImpactTop of page
Some Buxus species are endangered or threatened (Batdorf, 2004); introduction of the rust to their native regions could add to the threats to their survival.
Social ImpactTop of page
Risk and Impact FactorsTop of page Invasiveness
- Proved invasive outside its native range
- Has a broad native range
- Abundant in its native range
- Tolerant of shade
- Host damage
- Parasitism (incl. parasitoid)
- Highly likely to be transported internationally accidentally
- Difficult to identify/detect as a commodity contaminant
DiagnosisTop of page
No DNA sequences of this species that could be used in laboratory identification of the fungus or detection of the fungus in plant tissue have been deposited in the GenBank database (NCBI, 2009) as of September, 2009.
Detection and InspectionTop of page
Both sides of the newest leaves of Buxus plants should be inspected for black pustules containing large, thick-walled, two-celled stalked spores. On plants without pustules, the newest leaves should be examined for spots accompanied by a thickening of the leaves.
Similarities to Other Species/ConditionsTop of page
No other rust fungi are reported on Buxus species. The asexual fungus Macrophoma candollei [Dothiorella candollei] also causes leaf spots on boxwood (Buxus sempervirens). Its small black pycnidia develop on the undersides of leaves, but the disease begins and is more severe on the oldest of the bush’s foliage, rather than on the newest leaves. The pycnidia produce tendrils, often called cirrhi, of single-celled spores (Batdorf, 1995).
Prevention and ControlTop of page
Gaps in Knowledge/Research NeedsTop of page
More information is needed on the biology and ecology of this rust fungus, including the means and conditions of dispersal and the conditions of temperature and humidity required for germination, infection, growth and sporulation.
ReferencesTop of page
BPI (US National Fungus Collections), 2009. Fungal Databases - Specimens. Beltsville, USA: Systematic Mycology and Microbiology Laboratory, Agricultural Research Service, USDA. www.nt.ars-grin.gov/fungaldatabases/specimens/specimens.cfm
Gonzalez Fragoso R, 1918. [English title not available]. (La roya de los vegetales. Enumeracion y distribucion geografica de los Uredales. Conocidos hasta hoy en la Peninsula Iberica e Islas Baleares. Trabajos del Museo Nacional de Ciencias Naturales.) Serie Botanica, 15:1-267.
Hiratsuka N; Sato S; Katsuya K; Kakishima M; Hiratsuka Y; Kaneko S; Ono Y; Sato T; Harada Y; Hiratsuka T; Nakayama K, 1992. The Rust Flora of Japan. Takezono, Ibaraki, Japan: Tsukuba Shuppankai, 1205 pp.
Huseyin E, 2005. Materials on the micromycetes of the box tree and rhododendron from Turkey. In: Proceedings of the 16th Symposium of Mycologists and Lichenologists of Baltic States, Cesis (Latvia), 21-25 September 2005. 62-68.
Liou TN, 1929. [English title not available]. (Note sur quelques Uredinees peu communes ou critiques recoltees dans le Midi, le Centre et l'Est de la France.) Bulletin de la Societe Mycologique de France, 45:197-215.
Llorens i Villagrassa I, 1984. Contribution to the knowledge of Uredinales, Ustilaginales and Phragmobasidiomycetes of Spain. I. (Aportación al conocimiento de los Uredinales, Ustilaginales y Fragmobasidiomicetos de España. I.) Anales de Biología, 1(Special Section 1):35-45.
NAPPO, 2006. Boxwood Rust (Puccinia buxi) incident in Pennsylvania. Official Pest Reports. Phytosanitary Alert System, North American Plant Protection Organization. Ottawa, Canada: North American Plant Protection Organization. http://www.pestalert.org/oprDetail.cfm?oprID=202&keyword=Puccinia%20buxi
USDA/APHIS, 2003. Final Rule for the Importation of Artificially Dwarfed Plants in Growing Media From the People's Republic of China. Washington DC, USA: USDA. http://www.aphis.usda.gov/plant_health/ea/downloads/penjingf.pdf
ContributorsTop of page
10/09/09 Original text by:
Distribution MapsTop of page
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