ORIGINAL ARTICLE Perpetuation of Cherry Leaf Spot Disease in Ornamental Cherry Jacqueline Joshua 1 and Margaret T. Mmbaga 1,2 1 College of Agriculture Human and Natural Sciences, Department of Agricultural and Environmental Sciences, Tennessee State University, 3500 John A. Merritt Blvd., Nashville, TN 37209, USA 2 Otis Floyd Nursery Research Center, Tennessee State University, 472 Cadillac Lane, McMinnville, TN 37110, USA Keywords disease management, flowering cherry, primary inoculum, Prunus serrulata, winter survival Correspondence M. T. Mmbaga, Department of Agricultural and Environmental Sciences, Tennessee State University, Nashville, TN, USA E-mail: mmmbaga@tnstate.edu Received: July 11, 2013; accepted: August 3, 2014. doi: 10.1111/jph.12309 Abstract Cherry leaf spot disease, caused by Blumeriella jaapii (Rehm) Arx., is an increasing concern to nursery producers of ornamental cherry in the south-eastern United States. Spores were trapped starting in late March before symptoms were observed in the field, which indicates that leaf deb- ris from diseased trees are an important source of primary inoculum. Pre- viously infected trees of six cultivars (‘Kwanzan’, ‘Yoshino’, ‘Okami’, ‘Snowgoose’, ‘Autumnalis’ and ‘Akebono’), which were overwintered in a controlled environment protected from airborne spores, developed dis- ease symptoms in late spring, indicating that dormant buds may also be a source of primary inoculum. Because ornamental cherry trees are propa- gated by budding and cuttings, disease management should incorporate cultural practices that focus on propagation from disease-free trees and fungicide applications beginning at petal drop to protect emerging leaves. Introduction Ornamental cherries also known as flowering cher- ries (Prunus species) grown solely for ornamental purposes have been decorating North America gardens and landscapes since 1862 (Pooler 2007). Ornamental cherries are popular landscape plants mostly because of their colourful springtime floral displays, fall foliage colour and ornamental bark. The aesthetic importance of ornamental cherry trees is demonstrated every year in Cherry Blossom Festivals featuring the Kwanzan cherry in Washington, DC, and other locations that celebrate their beauty including Macon, GA, Seattle, WA, San Diego, CA and Philadelphia, PA (Russel 1938). Deformities that diminish tree aesthetics affect sales and growers’ income. Cherry leaf spot disease (CLS) caused by the fungus Blumeriella jaapii (Rehm) Arx. (anamorph: = Phloeosporella padi (Lib.) Arx. Cylindrosporium padi (Lib.) Karst. ex. Sacc. [Synonym: Higginsia (Cocco- myces) hiemalis (B.B. Higgins) Nannf.]) is one of the most important diseases in ornamental cherries. Symptoms include premature defoliation, reduced shoot growth, increased susceptibility to winter injury which can significantly reduce tree aesthetics and market value and occasional mortality (Baba- doost 1995; Diaz et al. 2007). Economic significance of CLS has been recognized on fruiting cherry and plum species in many cherry- growing regions worldwide since the 1960s (Holb 2009). In the USA, most fruiting cherries are grown largely in the cooler northern and northwest regions (Shaughnessy 1999; Ellis 2008). Most studies on CLS disease have focused on sweet cherry (P. avium Rouy & Camus) and sour cherry (P. cerasus L.) in cooler regions where they are important crops (Williamson and Bernard 1988; Stanosz 1992; Garcia and Jones 1993; Jones 1995; Kiraly and Szentpeteri 2006). How- ever, CLS disease also affects other Prunus species including ornamental cherries that are widely grown in warmer south-eastern regions (Shaughnessy 1999). Cherry leaf spot disease is of increasing con- cern in nursery production of ornamental cherries and studies from fruiting cherries are not necessarily applicable to the south-eastern regions because of dif- ferences in weather. Previous studies have reported that B. jaapii over- winters on leaf debris as ascocarps (Eisensmith and J Phytopathol 163 (2015) 194–201 Ó 2014 Blackwell Verlag GmbH 194 J Phytopathol