Bay willow-larch rust - Melampsora larici-pentandrae

A number of rust fungi infect larch and willow trees and these are difficult to distinguish. However, unlike other Melampsora on Larix-Salix, the urediniospores of M. laricis-pentandrae have apices that are conspicuously thickened. Pei & McCracken (2005) present a recent account of these rust fungi.

Melampsora larici-pentandrae Kleb. 1897

Aecia caemoid, i.e. lacking a peridium, mainly hypophyllous (on lower surface of leaves), single or in small numbers, 0.25-1 mm; aeciospores in small chains, ovoid, round or slightly angler 18-26 × 13-20 µm, wall 1.5-2 µm thick, densely verrucose.

Uredinia mainly hypophyllous, in discoloured spots, 0.2-1 mm diam; urediniospores elliptical or ovoid, 26-44 × 12-24 µm, walls about 2 µm thick, distantly echinulate; paraphyses capitate or clavate, 40-70 µm long, × 12-22 µm diam at apex.

Telia hypophyllous, subepidermal, 0.5 mm, often confluent in crusts; teliospores prismatic, round at base and slightly angler at apex, 28-38 × 6-11 µm, walls 1 µm.

See Helfer (1992) and Pei et al. (1993) for a more detailed description.

Host range: Aecia develop on Larix decidua and L. occidentalis. Uredinia and telia occur on Salix fragilis and S. pentandra (bay willow).

Geographic distribution: Known primarily throughout Europe, recently reported from China (Zhuang, 2005).

References:

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

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

Foister, C.E. 1961. The economic plant diseases of Scotland. Techn. Bull. Dept. Agric. Fish. Scotland 1: 1-210.

Helfer, S. 1992. The rust diseases of willows in Britain. Proc. Roy. Soc. Edinburgh 98B: 119-134.

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

Pei, M.H., Royle, D.J., and Hunter, T. 1993. Identity and host alternation of some willow rusts (Melampsora spp.) in England. Mycol. Res. 97: 845-851.

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. Bay willow-larch rust - Melampsora larici-pentandrae. Retrieved November 21, 2009, from http://nt.ars-grin.gov/sbmlweb/fungi/index.cfm .