S. M. Stoxen and
D. S. Mollov, Department of Plant Pathology, University of Minnesota, 1991 Upper Buford Circle, St. Paul, MN; and
L. J. Szabo, USDA-ARS, Cereal Disease Lab, 1551 Lindig Street, St. Paul, MN
In September 2008, Veronica spicata ‘Royal Candles’ plants showing foliar symptoms typical of a rust infection were brought to the Plant Disease Clinic at the University of Minnesota. Plants were grown in a local nursery in Dakota County, Minnesota. A dark brown discoloration was apparent on the upper surface of the leaf with lighter brown pustules on the underside. Teliospores collected from the pustules were 2-celled with smooth walls and 36.35 to 48.87 μm long, 11.96 to 18.28 μm wide, and had a wall thickness of 1.33 to 2.61 μm, which is in accordance with type specimen of Puccinia veronicae-longifoliae (4). Pathogen identity was confirmed by comparison of the DNA sequence of nuclear ribosomal RNA region containing the internal transcribed spacer regions 1 and 2, 5.8S and the 5′ end of the 28S subunits between herbarium samples from the U.S. National Fungus Collection (BPI 841971/GenBank Accession JQ627617 and BPI 871789/GenBank Accession JQ627618) and the collected specimen (BPI 882886/GenBank Accession JQ627616). P. veronicae-longifoliae was first reported in the United States in 2004 from a commercial nursery in Michigan (2). Veronica rust has also been found in Michigan in 2005 and more recently in 2011 (1). The only other known report of Veronica rust in the United States occurred in Connecticut in 2007 (3). P. veronicae-longifoliae is not considered a quarantine pest by The Animal and Plant Health Inspection Service due to the limited host range, the host not being on the threatened or endangered list and the host being of little economic or environmental importance (2).
References: (1) T. A. Dudek et al. MSU Extension News. Retrieved from http://msue.anr.msu.edu/news/veronica_rust_observed_this_season/, 2011. (2) North American Plant Protection Organization's Phytosanitary Alert System. Retrieved from http://www.pestalert.org/oprDetail.cfm?oprID=129, 2004. (3) Pundt, L. Floriculture Greenhouse Update. Retrieved from http://www.negreenhouseupdate.info/index.php/july/194-rust-on-veronica, 2007. (4) D. B. O. Savile. Can. J. Bot. 46:631, 1968.