Disease Note

Report of Tomato Spotted Wilt Virus on Thanksgiving Cactus. M. K. Hausbeck, Department of Plant Pathology, Pennsylvania State University, University Park 16802. F. E. Gildow, Department of Plant Pathology, Pennsylvania State University, University Park 16802. Plant Dis. 75:215. Accepted for publication 27 September 1990. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-0215C.

During a survey of greenhouse ornamentals in Pennsylvania for tomato spotted wilt virus (TSWV), the impatiens (TSWV-I) and lettuce (TSWV-L) strains of TSWV were detected in the Thanksgiving cactus (Schlumbergera truncata (Haw.) Moran). A total of 28 samples of S. truncata were collected at seven locations representing five counties. Samples did not show thrips or thrips damage, although western flower thrips had previously been observed at some grower locations. TSWV in S. truncata was determined serologically by enzyme-linked immunosorbent assay (ELISA) using a polyclonal antiserum to TSWV-I (Agdia, Elkhart, IN) and TSWV-L (Pennsylvania Department of Agriculture, Harrisburg). All samples were retested to verify strain identity. Incidence of TSWV-I and TSWV-L was 21 and 39%, respectively, representing four locations and counties. Sap from selected samples infected with TSWV was used to inoculate Chenopodium quinoa Willd. and Lycopersieon esculentum Mill., and infection by TSWV was verified by ELISA. S. truncata infected with either TSWV isolate typically showed a range of mild symptoms that included sunken chlorotic lesions, dark green spots, chlorosis, necrosis, and distortion. TSWV-L was also isolated from symptomless S. truncata. The characteristic ring pattern associated with TS WV on various other host plants was not observed. The S. truncata had originated from commercial propagators and had been held beyond the typical growing season. In at least one location, S. truncata was a common denominator for two nonoverlapping gloxinia crops that tested positive for TSWV. The role of S. truncata as a reservoir for TSWV and the difficulty in detecting TSWV on this host because of uncharacteristic or no symptom expression are important considerations in management strategies.