First Report of Black Locust Anthracnose Caused by Colletotrichum gloeosporioides in Georgia and South Carolina. E. C. Whiting, Department of Plant Pathology; University of Georgia, Athens 30602. R. W. Roncadori, Department of Plant Pathology, and B. C. Bongarten, School of Forest Resources, University of Georgia, Athens 30602. Plant Dis. 78:529. Accepted for publication 1 March 1994. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-0529D.
During July 1991 and 1992, up to 95-100% of black locust (Robinia pseudoacacia L.) suffered 25-50% defoliation in a plantation near Greensboro, Georgia. Numerous dark brown to black leaf spots (1-3 mm diameter) and dark gray to black necrotic areas along leaflet margins were observed on chlorotic abscised leaflets. Symptoms were also observed on black locust in natural stands in Georgia and South Carolina in August and September of 1992 and June of 1993. Colletotrichum gloeosporioides (Penz.) Penz. & Sacc, in Penz, was isolated from leaf spots and from necrotic tissue at leaflet margins and on petioles. Koch's postulates were tested for by spraying 1.6 x 107 spores per milliliter on healthy leaves of 2-yr-old, greenhouse-grown, rooted shoot cuttings and placing the plants in a mist chamber for 24 hr at 20 C. After 7 days on a greenhouse bench, symptoms developed, and the fungus was isolated from 434 of 435 necrotic areas. Black locust is grown as a source of biomass in Georgia, but susceptibility lo anthracnose may limit its use in intensively managed plantations.