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Seasonal behaviour of citrus variegated chlorosis in three regions of São Paulo State, Brazil

This work was to characterize the evolution of Citrus variegated chlorosis (CVC) related variables in plants of three regions in the State of São Paulo (Northeast, Center and South), in order to demonstrate differences in seasonal pattern of the pathogen, Xylella fastidiosa, vectors (sharpshooters), host [sweet orange (Citrus sinensis) 'Pera' grafted on Rangpur lime (Citrus limonia)] and disease. Twenty symptomatic plants were evaluated monthly from December 1998 to December 2000. The following variables were measured: number of new flushes (nf), percentage of symptomatic branches (psb), percentage of infected assymptomatic branches (piab), percentage of infected branches (pib), estimation of bacteria concentration (ebc), lower and higher temperatures, rain fall and number of sharpshooters in yellow traps. The correlations among variables were tested by Distributed Lag Analysis and the comparison between regions and season was performed by Kruskal-Wallis and Friedman ANOVA and Nemenyi test (p<0,005). The CVC related variables (psb, piab, pib and ebc) showed seasonal patterns but no statistical differences were detected among seasons. The Northeast orchard showed the highest number of new flushes and percentage of symptomatic branches. The South orchard had the higher percentage of assymptomatic infected branches. There were no statistical differences among regions regarding the concentration of Xylella.


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