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Puccinia psidii infects several genera and a number of species in the Myrtales, which includes economically important tree crops such as Eucalyptus spp, Pimento officinalis (allspice), Psidium guajava (guava), and Syzygium aromaticum (clove). Puccinia psidii is endemic to the Americas. Although Eucalyptus originated in Australia and the Southeast Asia region, these hosts are susceptible to P. psidii. The rust can produce significant yield losses on seedlings and young trees in the New World and is a potential threat to the several million hectares of Eucalyptus plantations around the world. Because of this, much effort is going into keeping the rust from spreading to new areas (Coutinho et al 1998). Puccinia psidii causes a severe disease of guava infecting leaves, stems and fruits, causing defoliation and mummifying fruits when the infection occurs early. This rust also attacks foliage, inflorescences, and young succulent fruits of Pimento, Eucalyptus and Syzygium. Puccinia psidii G. Winter Spermogonia and aecia unknown. Uredinia amphigenous, although mostly hypophyllous, caulicolous, and on flowers and fruits; when on leaves in groups on brownish or blackish spots up to 5 mm diam, subepidermal, becoming erumpent, pale yellow when young, later pale yellow-orange, pulverulent, 0.1-0.5 mm diam; urediniospores globose, ellipsoid to obovoid, 19-27 × 15-26 µm, wall hyaline to yellowish, 1.5-2.5 µm thick, echinulate, germ pores obscure. Telia similar to uredinia or teliospores in uredinia; teliospores ellipsoid to oblong, rounded at apex, narrow below, slightly constricted at septum, 30-48 × 17-22 µm, wall 1.5-2.5 µm thick at sides, 2-4 µm thick at the apex, pale yellowish, smooth; pedicel, colorless, deciduous. Hosts: Myrtales in the families Heteropyxidaceae on the genus Heteropyxis (Alfenas et al 2005), and Myrtaceae on the genera Abbevillea, Callistemon, Calycorectes, Campomanesia, Eucalyptus, Eugenia, Jambosa, Marlierea, Melaleuca, Myrcia, Myrciaria, Phyllocalyx, Pimenta, Pseudomyrcianthes, Psidiopsis, Psidium, Siphoneugena, and Syzygium (Farr, D.F., Rossman, A.Y., Palm, M.E., & McCray, E.B. (n.d.) Fungal Databases, Systematic Botany & Mycology Laboratory, ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/). Geographic distribution: Puccinia psidii is native to the warmer regions of the western hemisphere. It is reported from Argentina to Florida in the USA. Reports from other areas are unreliable. Several other rusts have been described on the Myrtaceae. Phakopsora rossmaniae Dianese, L.T.P. Santos & D.J. Tessman on Campomanesia adamantium (Cambess.) O. Berg from Brazil has uredinia with peripheral paraphyses, while uredinia of P. psidii have no paraphyses. Puccinia cygnorum R.G. Shivas & J. Walker on Kunzea ericifoliae (Sm.) Rchb. ex Heynh. from Australia lacks uredinia and has teliospores measuring 35-60 × 12-20 µm, while P. psidii produces uredinia, and has teliospores measuring 30-48 × 17-22 µm. Uredo seclusa H.S. Jacks. & Holw. on undetermined Myrtaceae from Brazil has urediniospores with 2-3 super-equatorial germ pores, while in P. psidii the germ pores are obscure. References: Alfenas, A.C., Zauza, E.A.V., Wingfeld, M.J., Roux, J., and Glen, M. 2005. Heteropyxis natalensis, a new host of Puccinia psidii rust. Australas. Pl. Pathol. 34: 285-286. Coutinho, T.A., Wingfield, M.J., Alfenas, A.C., and Crous, P.W. 1998. Eucalyptus rust: a disease with the potential for serious international implications. Pl. Dis. 82: 819-825. Hennen, J.F., Hennen, M.M., and Figueiredo, M.B. 1982. [Index of the rust fungi (Uredinales) of Brazil]. Arch. Inst. Biol. (Sao Paulo), Suppl. 1 49: 1-201. Laundon, G.F., and Waterston, J.M. 1965. Puccinia psidii. C.M.I. Descr. Pathog. Fungi Bact. 56: 1. Lindquist, J.C. 1982. Royas de la Republica Argentina y Zonas Limitrofes. Inst. Nacional de Tecnologia Agropecuaria., 574 pages.
Suggested citation: Hernández, J.R. Systematic Mycology and Microbiology Laboratory, ARS, USDA. 27 February 2006. Invasive Fungi.
Systematic Mycology and Microbiology Laboratory
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