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Preliminary Analysis of Citrus Greening (Huanglungbin) Epidemics in the People’s Republic of China and French Reunion Island. T. R. Gottwald, Research plant pathologist, U.S. Department of Agriculture, Agricultural Research Service, Orlando, FL 32803; B. Aubert(2), and Zhao Xue-Yuan(3). (2)UNDP-FAO Regional Project Coordinator, Fujian Academy of Agricultural Sciences, No. 41 Hualin Road, Fuzhou, People’s Republic of China; (3)Vice-Director, Chinese Academy of Agricultural Sciences, Citrus Research Institute, Beibei, Chongqing, People’s Republic of China. Phytopathology 79:687-693. Accepted for publication 9 February 1989. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1989. DOI: 10.1094/Phyto-79-687.

Epidemics of citrus greening disease in sweet orange groves were monitored for several years at two sites in the Guangxi Province of the People’s Republic of China and one site in French Reunion Island. Both the exponential and the logistic models adequately described the increase of greening expressed as disease incidence over time in two plots in China and when the disease was expressed as both disease incidence and disease severity for the Reunion Island plot. The logistic apparent infection rates, r, were 2.53, 1.87, and 0.99/yr for disease incidence at the two Chinese and one Reunion plots, respectively, and 1.04/yr for disease severity in the Reunion plot. Ordinary runs analysis indicated aggregation of diseased trees in all plots during all years except in the case of one plot in China when disease incidence exceeded 0.99. Aggregation along rows of the Reunion plot was associated with prevailing winds. Isopaths of greening disease incidence demonstrated the highest level of disease was present in the western half of the Reunion plot. This spatial pattern suggested the pathogen was introduced from the west against the prevailing winds, probably by psyllid vectors.

Additional keywords: likubin, citrus yellow shoot, citrus vein phloem degeneration, Diaphorina citri, Triosa erytreae, Lloyd’s index of patchiness, spatial lag order autocorrelation.