Tidskrift/serie: Data Sheets on Quarantine Pests
Utgivare: CAB International in association with EPPO
Redaktör: Smith I.M. (EPPO), McNamara D.G. (EPPO), Scott P.R. (CABI), Harris K.M. (CABI)
Utgivningsår: 1992
Nr/avsnitt:
Författare: Anonymous
Adress:
Ingår i...: Quarantine Pests for Europe
Titel: Gymnosporangium spp. (non-European)
Huvudspråk: Engelska
Målgrupp: Rådgivare
Gymnosporangium spp. (non-European)
Fungi: Basidiomycetes: Uredinales
For information on the taxonomy of Gymnosporangium spp. see Kern (1973).
No. 13
Of the Gymnosporangium spp. which do not occur in the EPPO region, the following six are considered the most important.
Gymnosporangium asiaticum Miyabe ex Yamada
Gymnosporangium haraeanum H. Sydow & Sydow
Gymnosporangium chinense Long
Gymnosporangium koreaense Jackson
Gymnosporangium spiniferum H. Sydow & Sydow
Roestelia koreaensis P. Hennings
Pear-juniper rust (English)
GYMNAS
I/A1
Gymnosporangium clavipes (Cooke & Peck) Cooke & Peck
Gymnosporangium germinale Kern
Podisoma gymnosporangium-clavipes Cooke & Peck
Caeoma germinale Schweinitz
Roestelia aurantiaca Peck
Quince rust (English)
GYMNCL
I/A1
Gymnosporangium globosum (Farlow) Farlow
Gymnosporangium fuscum var. globosum Farlow
American hawthorn rust (English)
GYMNGL
I/A1
Gymnosporangium juniperi-virginianae Schwein
Gymnosporangium macropus Link
Gymnosporangium virginianum Sprengel
Aecidium pyrolatum Schwein
Roestelia pyrata Thaxter
Cedar-apple rust (English)
GYMNJV
I/A1
Gymnosporangium shiraianum K. Hara
Pear-juniper rust (English)
GYMNSH
I/A1
Gymnosporangium yamadae Miyabe ex Yamada
Apple-juniper rust (English)
GYMNYA
I/A1
Gymnosporangium
species Aecial hosts Telial hosts
G. asiaticum Pyrus Juniperus sect. Sabina
(J. chinensis)
Chaenomeles
Cydonia
Photinia
G. clavipes Cydonia Juniperus sect.
Oxycedrus (J. communis
including J. sibirica)
Juniperus sect. Sabina
(J. virginianae)
Malus
Crataegus
G. globosum Crataegus Juniperus sect. Sabina
(J. virginianae)
Malus
Pyrus
Sorbus
G. juniperi-
virginianae Malus Juniperus sect. Sabina
(J. virginianae and
related spp.)
G. shiraianum Pyrus Juniperus sect
Oxycedrus (J. conferta)
G. yamadae Malus Juniperus sect. Sabina
The aecial hosts are important crops, grown throughout the EPPO region, and in addition the telial hosts, Juniperus spp., are also present, mostly as ornamentals.
Absent.
Absent.
USA (California, Connecticut, Oregon and Washington).
China, Hong Kong, Japan and Korea.
See CMI (1979b, No. 530).
Canada (widespread), Mexico, USA.
See CMI (1975, No. 121).
Canada (widespread in east), Mexico, USA (widespread in eastern states, also Alaska).
See CMI (1989, No. 123).
Canada (Ontario, Quebec), USA (widespread east of the Rockies, also California).
See CMI (1965, No. 61).
Japan.
China, Japan and Korea.
See CMI (1979a, No. 528).
All six species are heteroecious in that they require Juniperus and rosaceous hosts to complete their life cycles. Telia are produced on stems, green shoots and leaves of Juniperus in the spring. In moist conditions, the telia germinate in situ and produce basidiospores which are dispersed and are able to infect nearby rosaceous hosts. Infection of J. chinensis by G. asiaticum is known to be persistent for more than 1 year (unpublished work in the UK), as is also the infection by G. yamadae and by G. globosum.
Infection from basidiospores gives rise to pycnia borne on the upper surface of the leaves of the rosaceous host; they are visible from late spring to early summer. Later, aeciospores are produced inside tubular protective sheaths (peridia) on the underside of the leaf. Aecia of G. clavipes typically appear on fruit and this can also occur for G. juniperi-virginianae. It is inferred that fruit infection may be possible for other species. The aeciospores are released when the peridium ruptures and are capable of being wind-borne over long distances to Juniperus. After germinating on the Juniperus host, an overwintering latent mycelium is produced. Infection of the rosaceous host does not persist after infected leaves or fruits have fallen.
The telial state appears on Juniperus in the spring to begin the life cycle again.
For more information see Tanaka (1922), Peterson (1967).
On Juniperus, these Gymnosporangium spp. cause galls on twigs, branches and leaves or fusiform swellings on stems (G. yamadae) which can produce telial horns under wet conditions (see Morphology).
On aecial hosts, symptoms correspond to the observation of aecia and pycnia on leaves (see Morphology). On susceptible cultivars, G. juniperi- virginianae and G. yamadae can cause very severe defoliation. Infections on fruits are rare with G. globosum and G. yamadae. Occasionally G. juniperi- virginianae can cause superficial brown necrotic lesions on apples. G. clavipes is more serious on quince fruits and apples and can cause dark-green lesions at the calyx end extending to the core and distortions of the fruits.
Telia: In G. asiaticum, G. clavipes and G. shiraianum, these are in the form of small cushions of orange-brown spores, 1-3 mm in diameter, on or among the foliage. G. yamadae causes swelling of the stems, and the teliospores are produced in tongue-shaped yellowish-red masses, 3-5 mm long (ramicolous infection has also been observed in G. asiaticum).
The telia of G. juniperi-virginianae are formed on globoid or reniform galls 1-3 cm in diameter on the sides of twigs or branches. They are long- cylindric, tapered, 10-20 mm long x 1-2 mm wide, rusty-brown.
The telia of G. globosum are formed on globoid galls, 3-10 mm on the sides of twigs or branches. They are conic, 3-12 mm high x 1.3 mm wide, chestnut-brown.
Teliospores: Two-celled, cylindric-fusoid (G. juniper-virginianae) or ellipsoid (other species). Teliospores of G. clavipes are constricted at the septum, often have the upper cell broader than the lower, and often have distinctively long swollen pedicels, 10-25 µm wide.
G. asiaticum: 15-25 x 32-47 µm wall, 1-1.5 µm thick.
G. clavipes: 20-28 x 35-60 µm wall, 0.5 µm thick.
G. globosum: 35-40 x 17-24 µm wall, 0.5-2.5 µm thick.
G. juniperi-virginianae: 15-21 x 35-65 µm wall, 0.5-1 µm thick.
G. shiraianum: 15-25 x 30-60 µm wall, 1.5-2.5 µm thick.
G. yamadae: 15-24 x 32-45 µm wall, 1-1.5 µm thick.
Aecia: Roestelioid, hypophyllous (fructicolous in G. clavipes) with the peridia 3-5 mm high (2 mm in G. clavipes). Dehiscent at the apex (G. asiaticum, G. shiraianum, G. juniperi-virginianae) or lacerate at the sides (G. globosum and G. yamadae) or both (G. clavipes). The aeciospore mass is reddish-brown in G. juniperi-virginianae, rusty-brown in G. asiaticum and G. globosum, chestnut-brown in G. yamadae, fulvous in G. shiraianum and orange fading to white in G. clavipes.
Aeciospores: Those of most species are similar in diameter (15-28 µm) but those of G. clavipes are larger (28-36 µm). Details can be found in the CMI Descriptions (Laundon, 1977).
The inspection of imported Juniperus which may have latent infection is particularly important. A secure quarantine procedure would involve retention under closed conditions for 2 years and frequent inspection during January- May.
Under natural conditions these rusts spread by basidiospore dispersal on rosaceous hosts, and by wind-borne aeciospores on Juniperus. In international trade, all vegetative material of Juniperus from the Far East and North America is liable to be infected by the appropriate species. The rusts can be latent during winter (the probable importing period) and may not be detectable at pre-export phytosanitary certification. Infection may also have remained latent on the plants in the previous growing season. G. asiaticum has been intercepted on dwarf (bonsai) Juniperus from Japan and Hong Kong.
Introduction on commercial importations of rosaceous hosts is very unlikely as infection is not persistent in the dormant stage of this host. During the summer months, travellers' baggage may contain rosaceous trees or shrubs which could introduce rusts.
G. asiaticum and G. yamadae are known to be of economic importance, but the status of G. shiraianum is uncertain. G. juniperi-virginianae is the most serious Gymnosporangium disease in the USA while G. clavipes and G. globosum can respectively be severe on apple fruit and on hawthorn seedlings, apple tree leaves (fruits are rarely attacked) and Juniperus.
G. juniperi-virginianae, G. globosum and G. clavipes can be adequately controlled on apples by routine fungicide applications (e.g. sterol-inhibiting fungicides). The same probably applies to the other species on apples and pears.
Varietal differences in susceptibility are well known for G. juniperi- virginianae and are also known for G. clavipes and G. asiaticum. There is a reference to immunity from infection by G. yamadae. Selection of resistant cultivars can help to reduce the impact of the disease. Suppression of the alternate host (Juniperus spp.) is difficult as they are often present in private gardens.
Gymnosporangium spp. (non-European) are listed as A1 quarantine organisms by EPPO (OEPP/EPPO, 1983). COSAVE lists G. clavipes, G. globosum and G. juniperi-virginianae; IAPSC lists all the EPPO-listed species except G. shiraianum; JUNAC lists G. juniperi-virginianae. G. asiaticum is also listed as a quarantine pest by NAPPO.
In common with other Gymnosporangium spp., several of which already occur in Europe, the severity of infection on the rosaceous host (generally the more important host) is determined by the proximity of infected alternate hosts. The basidiospores, being short-lived, are not capable of airborne infection over long distances. There is a possibility that these fungi could become established on junipers in Europe, as both Oxycedrus and Sabina types occur naturally and as planted ornamentals.
As infection of junipers is systemic in stems and evergreen leaves, no chemical treatment is likely to be completely effective. The use of actidione has been recommended for the suppression of teliospore production of G. juniperi-virginianae in the USA and this may be used as a short-term quarantine treatment of infected plants pending destruction. It is most unlikely that infection from the telial stage could be carried on packing materials and the risk is virtually confined to infected plants. EPPO proposes (OEPP/EPPO, 1990) that all countries may prohibit importation of plants for planting and cut branches of Juniperus from Asia and North America. If plants for planting of Juniperus are imported from these areas, the consignment should be kept in quarantine over the growing season and found free from Gymnosporangium spp. All countries should require that plants for planting and cut branches of Juniperus from Asia and North America must come from a field found free, with its immediate vicinity, of these diseases during the last two growing seasons. And all countries should require that plants for planting and cut branches of Crataegus, Cydonia, Malus, Photinia and Pyrus from Asia and North America should be dormant and free from leaves.
CMI (1965) Distribution Maps of Plant Diseases No. 61 (edition 2). CAB International, Wallingford, UK.
CMI (1975) Distribution Maps of Plant Diseases No. 121 (edition 2). CAB International, Wallingford, UK.
CMI (1979a) Distribution Maps of Plant Diseases No. 528 (edition 1). CAB International, Wallingford, UK.
CMI (1979b) Distribution Maps of Plant Diseases No. 530 (edition 1). CAB International, Wallingford, UK.
CMI (1989) Distribution Maps of Plant Diseases No. 123 (edition 3). CAB International, Wallingford, UK.
Kern, F.D. (1973) A revised taxonomic account of Gymnosporangium, 134 pp. Penn State University Press. See references to papers by: Fukushi, T. (1925); Hara, K. (1915); Hiratsuka, N. (1926, 1936, 1954); Hiratsuka, N. & Hitoni, G. (1924); Ishikawa, T. (1918); Kawakami, K. (1921); Tai (1929, 1930, 1933).
Laundon, G. (1977) Gymnosporangium asiaticum, Gymnosporangium clavipes, Gymnosporangium globosum, Gymnosporangium juniperi-virginianae, Gymnosporangium yamadae. CMI Descriptions of Pathogenic Fungi and Bacteria Nos 541, 543, 546, 547 and 550. CAB International, Wallingford, UK.
OEPP/EPPO (1983) Data sheets on quarantine organisms No. 13, Gymnosporangium spp. [Non-European]. Bulletin OEPP/EPPO Bulletin 13 (1).
OEPP/EPPO (1990) Specific quarantine requirements. EPPO Technical Documents No. 1008.
Peterson, R.S. (1967) Studies of juniper rusts. The West Madrono 19, 79- 91.
Tanaka, T. (1922) New Japanese fungi. Notes and translations XII. Mycologia 14, 282-287.