Rust of European blackberry - Phragmidium bulbosum

Although relatively common in Europe and also found in Asia, this rust does not attack economically important species of Rubus and thus does not appear to be threat to the berry industry in North America.

Phragmidium bulbosum (F. Strauss) Schltdl. 1824

Spermogonia epiphyllous (on upper surface of leaves), aggregated in minute groups opposite aecia, indefinite, becoming fused, subcuticular, 25-30 µm high.

Aecia hypophyllous (on lower surface of leaves), caeomoid, circular or annulate, up to 1 mm diam, orange, paraphysate; aeciospores globose to broadly ellipsoid, 25-22 × 23-16 µm, wall hyaline, coarsely verrucose with broad shallow warts up to 3 µm diam, 1.5-2 µm thick, pores obscure.

Uredinia hypophyllous, irregularly scattered without spots or on small reddish, yellowish, brownish, or purplish spots, occasionally on larger purplish blotches, 0.1-0.3 mm diam, yellowish, paraphysate. Urediniospores obovoid to ellipsoid, 19-24 × 16-18 µm, wall hyaline, coarsely echinulate, spines 1-2 µm apart, 0.5 µm high, 1-2 µm thick, pores 2.5-4 µm diam, obscure. Paraphyses cylindric-clavate, incurved, 40-60 × 8-13 µm, wall thickened to 2-3 µm at apex.

Telia scattered or aggregate, minute, round or irregular, black. Teliospores cylindric, not constricted at septa, apex rounded and with a blunt apiculus, up to 13-19 long × 5-7 µm wide, 4-7 celled, dimensions excluding apiculus: 4-celled 59-71 × 30-37 µm, 5-celled 73-89 × 32-37 µm, 6-celled 86-104 × 32-37 µm, 7-celled 98-111 × 32-36 µm; wall sienna to dark umber brown, verrucose, 4-5 µm thick, pores 2-4 in each cell; pedicels 75-160 long, 7-10 µm wide at neck, swollen below to 13-19 µm wide.

See Laundon & Rainbow (1969), Petrova & Denchev (2004), and Wilson & Henderson (1966) for a more detailed description.

Host range: Primarily reported on Rubus subgenus Rubus, specifically R. caesius (European dewberry) , R. canescens, R. grabowskii, R. hirtus, R. hispidus, R. montanus, R. plicatus, R. praecox, R. sanctus, R. ulmifolius, and R. vestitus but also known from Rubus subgenus Idaeobatus, specifically R. idaeus (raspberry), R. pungens, as well as a few other hosts, although some may be misidentifications.

Geographic distribution: Asia (China, Iraq, Pakistan); Europe (widespread).

Notes: Although this rust attacks a wide range of species of Rubus, none are closely related to economically important species. One host, Rubus vestitus, is a weedy plant that has become naturalized in the USA (OR, WA). Among those species of Phragmidium on Rubus that exist primarily outside of North America but in Europe are P. acuminatum, P. arcticum, and P. bulbosum. Phragmidium arcticum occurs only at northern latitudes including in northern Canada. Phragmidium acuminatum and P. bulbosum can be distinguished by finely echinulate urediniospores of P. acuminatum versus the coarsely echinulate urediniospores of P. bulbosum. One of the other species of Phragmidium on Rubus in Europe, P. rubi-idaei, is widespread in North America. Phragmidium violaceum known primarily from Europe, Africa, and introduced into Australia as a biocontrol agent, was recently discovered in western North America.

References:

Adamska, I. 2001. Microscopic fungus-like organisms and fungi of the Slowinski National Park. II. (NW Poland). Acta Mycol. 36: 31-65.

Ahmad, S. 1969. Fungi of West Pakistan. Biological Society of Pakistan Monograph. 5 (Sup.1): 1-110.

Braun, U. 1982. Die Rostpilze (Uredinales) der Deutschen Demokratischen Republik. Feddes Repert. Beih. 93: 213-334.

Gjaerum, H.B. 1982. Rust fungi from Madeira. Bol. Mus. Munic. Funchal 34: 5-22.

Henderson, D.M. 2000. Checklist of the Rust Fungi of the British Isles. British Mycological Society, 36 pages.

Hylander, N., Jorstad, I., and Nannfeldt, J.A. 1953. Enumerato Uredinearum Scandinavicarum. Opera Bot. 1: 1-102.

Jorstad, I. 1962. Investigations on the Uredinales and other parasitic fungi in Mallorca and Menorca. Skr. Norske Vidensk.-Akad. Oslo, Mat.-Naturvidensk. Kl. 2: 1-73.

Kirk, P.M., and Spooner, B.M. 1984. An account of the fungi of Arran, Gigha and Kintyre. Kew Bull. 38: 503-597.

Laundon, G.F., and Rainbow, A.F. 1969. Phragmidium bulbosum. C.M.I. Descr. Pathog. Fungi Bact. 203: 1-2.

Petrova, R.D., and Denchev, C.M. 2004. A taxonomic study of Phragmidiaceae (Uredinales) in Bulgaria. Mycol. Balcan. 1: 95-115.

Ryzhkin, D.V., and Levkina, L.M. 2004. Rust fungi of the North-East of Republic Mordovia. Mikol. Fitopatol. 38: 45-50.

Zhuang, W.-Y., Ed. 2005. Fungi of northwestern China. Mycotaxon, Ltd., Ithaca, NY, 430 pages.

Nomenclature

Specimens in BPI

Additional distribution data

Suggested citation: Yun, H.Y. Systematic Mycology and Microbiology Laboratory, ARS, USDA. . Invasive Fungi. Rust of European blackberry - Phragmidium bulbosum. Retrieved November 21, 2009, from http://nt.ars-grin.gov/sbmlweb/fungi/index.cfm .