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Disease Note.

First Report of Pleiochaeta setosa Leaf Spot on Genista tinctoria in Oregon. V. Sahakian, Monrovia Nursery Co., Dayton, OR 91702 . J. K. Stone, Department of Botany and Plant Pathology, Oregon State University, Corvallis 97331-2902. Plant Dis. 80:710. Accepted for publication 4 April 1996. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-0710C.

In spring 1993, a serious leaf spot occurred on Genista tinctoria L. (common Gold Woadwaxen) cv. Royal Gold grown in containers at a commercial nursery in Oregon. Affected plants had been kept in a hoop-house covered by white polyethylene film for winter protection from late November until late February; symptoms first became apparent in mid to late March. Black leaf spots 1 to 3 mm in diameter developed in the central area of the leaves along the midrib. Isolations from the leaf spot margins consistently produced Pleiochaeta setosa (Kirchn.) S. J. Hughes. Leaves that developed later in summer did not display leaf spot and /' setosa could not be isolated from the asymptomatic tissue. To test pathogenicity, one group of 12 plants was kept outdoors without winter protection and another group of 12 plants was kept in a separate hoophouse isolated from the main crop. Leaf debris was removed from the containers and in early February, just prior to bud opening, six plants in each group were sprayed to runoff with a suspension of 1 x 107 conidia/ml. Six control plants in both groups were sprayed with water. No symptoms were observed among either group kept outdoors. Noninoculated plants in the hoophouse developed minor incidence, with 2 to 4 spots per leaf on about 50% of leaves; inoculated plants had severe infection with almost 100% of leaves developing 5 to 8 leaf spots. Infection of noninoculated plants may have originated from residual leaf debris in containers. Isolations from the margins of leaf spots from both groups produced only P. setosa. The general crop of Royal Gold developed the same leaf spot symptoms in spring 1994 as in 1993 and P. setosa was again isolated consistently. This fungus has previously been reported as a Seedborne pathogen of lupines and other leguminous hosts worldwide. Its occurrence in North America is common in the southern United States, although it has also been recorded from Ontario, New Brunswick, Nova Scotia, (2), and Minnesota (1). This is the first record of this pathogen on an ornamental nursery crop in western North America.

References: (1) R. A. Kalis-Kuznia et al. Mycologia 83:826, 1991. (2) T. C. Paulitz and G Atlin. Plant Dis. 76:1185, 1992.