|Bassanezi, R. B. - FUNDO DE DEFESA DA CITRI|
|Bergamin Filho, A. - UNIV. OF SAO PAULO|
|Amorim, Lillian - UNIV. OF SAO PAULO|
Submitted to: International Organization of Citrus Virologists Proceedings
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 18, 2005
Publication Date: March 18, 2005
Citation: Bassanezi, R., Bergamin Filho, A., Amorim, L., Gottwald, T.R. 2005. Spatial and temporal analysis of citrus sudden death in brazil. International Organization of Citrus Virologists Proceedings. Technical Abstract: Citrus Sudden Death (CSD) is a disease of unknown etiology that affects sweet orange grafted on Rangpur lime and Volkamerian lemon in Brazil. Ordinary runs analysis of CSD-symptomatic trees indicated a departure from randomness of symptomatic trees status among immediately adjacent trees mainly within rows. The binomial index of dispersion for various quadrat sizes suggested aggregation of CSD-symptomatic trees for almost all plots within the quadrat sizes tested. Estimated parameters of the binary form of Taylor's power law provided an overall measure of aggregation of CSD-symptomatic trees for all quadrat sizes tested. Spatial autocorrelation analysis of proximity patterns suggested that aggregation often existed among quadrats of various sizes up to three lag distances; however, significant lag positions discontinuous from main proximity patterns were rare indicating a lack of spatial association among discrete foci. These results were interpreted to mean that the cause of the disease was biotic and its dissemination was common within a local area of influence that extended to approximately six trees in all directions, including adjacent trees. Annual rates of CSD progress based on the Gompetz model had the same range of tristeza progress rates and many similarities were found between the spatial patterns of citrus tristeza virus and CSD, in the presence of Toxoptera citricida. Based on the symptoms of CSD and on its spatial and temporal patterns, our hypothesis is that CSD may be caused by a similar pathogen such as a virus and probably vectored by insects such as aphids by similar spatial processes.