Comparative epidemiology of citrus tristeza in Cuba and citrus sudden death in Brazil

Abstract

Citrus Sudden Death (CSD) is a disease of unknown etiology, reported only in Brazil. Due to similarities between the epidemiology of CSD in Brazil and Citrus Tristeza (CT) in other countries, this work aimed to compare CSD and CT in Cuba. Besides testing the hypothesis of shared epidemiological patterns, the data generated can be used to carry out control strategies if CSD breaks out in Cuba. Seven epidemic data sets were statistically compared for each disease by analyzing their progress in time and the dependence among symptomatic or infected plants at two levels of spatial scale. CSD and CT epidemics could not be differentiated based on mean progress rate, area under disease progress curves, proportion of aggregated sequences (Ordinary runs test), index of Dispersion (D) or both parameters, log (A) and b, of the binary power law model. The progress rate of both diseases varied from low (0.0003/month) to very high (0.045/month). The proportion of aggregated sequences was low (<0.16) and D, log(A) and b values indicated aggregation in groups of 4 to 16 plants for both diseases. These results suggest that measures currently used for CT eradication and management in Cuba may be applied in case of an eventual introduction of CSD in that country. Keywords: Citrus tristeza virus, CTV, Closterovirus, Citrus sudden death associated virus, CSDaV, temporal pattern, spatial pattern. RESUMO Epidemiologia comparativa da tristeza dos citros em Cuba e morte súbita dos citros no BrasilA morte súbita dos citros (MSC) é uma doença de causa desconhecida relatada apenas no Brasil. Em função de semelhanças com a tristeza em outros países, objetivou-se comparar a MSC com a tristeza em Cuba. Além de testar a hipótese de similaridade dos padrões epidemiológicos, os dados gerados podem ser utilizados no delineamento de estratégias de controle no caso de uma eventual introdução da MSC em Cuba. Sete epidemias de cada doença foram comparadas estatisticamente por meio de análise do progresso no tempo e da dependência entre plantas sintomáticas ou infectadas em dois níveis de escala espacial. As epidemias de MSC e tristeza não puderam ser distinguidas com base na taxa média de progresso, na área abaixo da curva de progresso da doença, na proporção de seqüências agregadas (Ordinary Runs test), no índice de dispersão (D) ou nos parâmetros log(A) e b após ajuste da lei de Taylor binária. A taxa de progresso das epidemias de ambas as doenças foi variável, de baixa (0,0003/mês) a muito alta (0,045/mês). A proporção de seqüências agregadas foi baixa (<0,16) e os valores de D, log(A) e b indicaram agregação em grupos de 4 a 16 plantas tanto para a MSC quanto para a tristeza. Esses resultados indicam que as atuais medidas usadas no programa de erradicação e manejo da tristeza em Cuba poderiam ser usadas na eventualidade da introdução da MSC nesse país. Palavras-chave: Citrus tristeza virus, CTV, Closterovirus, Citrus sudden death associated virus, CSDaV, padrão temporal, padrão espacial.

Temporal clustering detection of disease in agricultural crops

“…Studies have suggested an aggregated spatial structure of symptomatic plants with CSD (Bassanezi et al, 2003;Bassanezi and Laranjeira, 2007), and shown that the CSD annual rate increases during periods under study (Bassanezi et al, 2003;Batista et al, 2008). The present work shows strong evidence of temporal clustering for CSD, which is mainly characterized by temporal clustering in the beginning of the trial.…”

“…In the current level of knowledge, these tests have not been used for temporal analysis of agricultural diseases. The majority of the temporal, specifically for CSD, are used for analyzing the disease behavior progression over time by estimating monthly rates (Batista et al, 2008) or by using spatial and temporal analyses (Bassanezi et al, 2005), models of cellular automata (Peixoto et al, 2008) and, autologistic models (Krainskiet al, 2008), rather than testing against the CTR hypothesis.…”

Rhynchosporium leaf scald disease incidence: seed source and spatial pattern

“…The apparent relationship between quadrat size and both the slope and intercept of the BPL regression has also been noted in previous field studies (e.g. Bassanezi et al ., ; Dallot et al ., ; Humeau et al ., ; Batista et al ., ). Although these results are clear, field studies that provide a basis for characterizing observed patterns of disease do not necessarily elucidate the process(es) underlying those patterns.…”