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First Report of Rust Caused by Uromyces Species on Birdsfoot Trefoil in the United States. K. E. Zeiders, U.S. Regional Pasture Research Laboratory, University Park, PA 16802. Plant Disease 69:727. 1985. Accepted for publication 20 March 1985. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-727a.

In late October 1983, a rust disease was observed on birdsfoot trefoil (Lotus corniculatus L.) growing in sod-seeded plots at the Pennsylvania Agricultural Experiment Station near State College.  The disease was found in seven of 15 plots and was also present on trefoil at five other sites within a 6-km radius.  Incidence in these areas ranged from trace to slight, but individual plants in sod-seeded plots were severely damaged.  Uredinia were mostly on leaflets, but stems were also infected.  Urediniospores were reddish brown, one-celled, spherical to slightly ellipsoid, and similar in size and morphology to spores of Uromyces striatus var. medicaginis (Pass.) Arth. from alfalfa (Medicago sativa L.).  Only the uredinial stage of the fungus has been observed.  Birdsfoot trefoil was readily infected by the Uromyces sp. in greenhouse inoculations; alfalfa and red clover (Trifolium pratense L.) were not infected.  The causal fungus is probably U. striatus var. loti (Blytt) Arth.  In August 1984, rust was prevalent in epidemic proportions in a birdsfoot-trefoil-seed-production nursery established in 1983; severely infected leaves turned yellow to bronze to reddish purple, shriveled, and finally dropped.  This outbreak of rust was a striking example of the potential of this new disease.