Occurrence of Citrus Greening Disease in Tanzania. I. S. Swai, Horticultural Research and Training Institute, Arusha, Tanzania. G. Evers, D. J. Gumpf, and Allan Femi Lana. Sokoine University of Agriculture, Morogoro, Tanzania; Department of Plant Pathology, University of California, Riverside 92521; and Plant Disease Clinic (EEC), Sokoine University of Agriculture, Box 3005, Morogoro, Tanzania. Plant Dis. 76:1185. Accepted for publication 24 June 1992. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-1185E.
A survey of 13,804 citrus trees in Tanzania during 1984-1990 revealed the presence of citrus greening disease and its psyllid vector, Trioza erytreae. The disease was prevalent at elevations over 800 m above sea level. Diseased trees typically were stunted and unthrifty with sparse foliage, had short twigs with narrow upright leaves, and had yellowish leaves with symptoms of zinc deficiency on one or more branches. Signs of zinc deficiency were common at all elevations, and the other symptoms were observed at elevations of 800-1,700 m. T. erytreae was detected in orchards at about 450 m, but disease was not found at these lower elevations. About 25% of the citrus checked above 800 m showed greening symptoms. Electron microscopic examinations of parts of trees with symptoms of citrus greening disease confirmed the presence of bacterialike organisms. The disease agent was graft-transmitted to healthy, greenhouse-grown indicator seedlings of Citrus sinensis (L.) Osbeck, C. aurantifolia (Christm.) Swingle, C. paradisi Macf., C. reshni Hort. ex Tan., and C. jarnbhiri Lush. This is the first report of citrus greening disease in Tanzania.