Asian rose rust-Gerwasia rosae

Species of Rosa including the commonly cultivated R. multiflora are attacked by a number of species of rust fungi many of which occur only in Asia and thus are potentially invasive in North America. Gerwasia rosae is known only in China. This fungus is similar to Gerwasia rubi in the shape of the teliospores but the latter occurs only on Rubus spp. At present, rust fungi on Rosa in North America belong primarily to the genus Phragmidium that produces large, dark teliospores.

Gerwasia rosae F.L.Tai 1947

Spermogonia and aecia unknown.

Uredinia hypophyllous (on lower side of leaf), usually closely grouped or diffuse, in pale yellowish spots, minute, usually less than 100 µm diam, yellowish when dry; paraphyses incurved, hyaline or nearly so, 1-septate near base, borne on basal cells with urediniospores, wall 35 µm thick on convex side, 1 µm on concave side; urediniospores ovoid, obovoid, or ellipsoid, 1625 × 2131 µm; wall 11.5 µm thick, hyaline or pale yellowish, echinulate, pores obscure but probably 3, equatorial and located in angles.

Telia hypophyllous, gregarious or scattered, round, pulvinate, 0.17-0.25 mm diam, white, erumpent through stoma, with incurved, hyaline, thick-walled paraphyses at outer part; teliospores and paraphyses formed superficially at one apex of a single or usually a bundle of sporogenous hyphae; teliospores ovoid or ellipsoid, thin-walled, less than 1 µm thick, hyaline, usually slightly attenuated at apex or rounded at both ends, 2641 × 1116 µm, forming a cylindrical 4-celled promycelium; pericel short, fragile, hyaline; paraphyses cylindrical, hyaline, strongly incurved, thick-walled, 33-51 × 7.8-9.2 µm.

See Cummins (1950) and Tai (1947) for a more detailed description.

Hosts: On species of Rosa, including Rosa banksiae var. normalis Regel Rosa cymosa Tratt., R. laevigata Michx., R. multiflora Thunb., R. roxburghii Tratt.

Geographic distribution: Known only from China (Fujian, Zhuang, 1983, Hubei, Guo, 1989, Hunan, Tai, 1947).

References:

Cummins, B.G. 1950. Uredinales of Continental China collected by S.Y. Cheo. Mycologia 42: 779-797.

Guo, L. 1989. [Uredinales of Shennongjia, China]. Fungi & Lichens Shennongjia, 107-156 pages.

Tai, F.L. 1947. Uredinales of Western China. Farlowia 3 : 95-139.

Zhuang, J.-Y. 1983. [A provisional list of Uredinales of Fujian Province, China.]. Acta Mycol. Sin. 2: 146-158.

Nomenclature

Specimens in BPI

Additional distribution data

Suggested citation: Yun, H.Y. Systematic Mycology and Microbiology Laboratory, ARS, USDA. . Invasive Fungi. Asian rose rust-Gerwasia rosae. Retrieved November 21, 2009, from http://nt.ars-grin.gov/sbmlweb/fungi/index.cfm .