Spatiotemporal characterization of citrus postbloom fruit drop inBrazil and its relationship to pathogen dispersal

Abstract

Citrus postbloom fruit drop (PFD) is caused by Colletotrichum acutatum and C. gloeosporioides. These pathogens attack the flowers and cause premature fruit drop and the retention of fruit calyces. This study was designed to characterize the spatial and temporal dynamics of PFD in commercial citrus-growing areas to better understand the disease spread. Experiments were carried out in three young orchards (500 trees each) in two municipalities in Sao Paulo State, Brazil. Symptoms of PFD on the flowers and presence of persistent calyces were assessed in each of three orchards for three years. Logistic, Gompertz and monomolecular models were fitted to the incidence data over time from the trees with symptoms. The spatial pattern of diseased trees was characterized by a dispersion index and by Taylor′s power law. An autologistic model was used for the spatiotemporal analysis. The logistic model provided the best fit to the disease incidence data, which had a fast progress rate of 0Á53 per day. During the early epidemic of PFD, the spatial pattern of diseased trees was random, which suggested that inoculum spread was due to mechanisms other than rain splash. As the disease incidence increased (up to 12Á6%), the spatial pattern of diseased trees became aggregated. The rapid rate of disease progress and the distribution of PFD suggest that dispersal of the pathogen is possibly related to a mechanism other than splash dispersal, which is more typical of other fruit diseases caused by Colletotrichum spp.

Suscetibilidade De Clones De Lima Ácida ‘Tahiti’ À Podridão Floral Dos Citros

“…A presença de cálices retidos em plantas cítricas é uma característica muito utilizada para auxiliar no diagnóstico da doença (KURAMAE-IZIOKA et al, 1997;FEICHTENBERGER et al, http://dx.doi.org/10.1590/0100-2945-060/15 H. B. Neto et al 2005. Os danos causados por PFC variam em função da quantidade e distribuição de chuvas durante o período de florescimento das plantas (LARANJEIRA et al, 2005;SILVA-JUNIOR et al, 2014). a doença é controlada com a aplicação sequencial de fungicidas (FEICHTENBERGER et al, 2005).…”

“…a doença é controlada com a aplicação sequencial de fungicidas (FEICHTENBERGER et al, 2005). Entretanto, devido ao curto período de incubação (aproximadamente quatro dias), o progresso da PFC é explosivo (SILVA-JUNIOR et al, 2014), o que reduz a eficácia do controle químico (KUPPER et al, 2003), além da possibilidade de ocorrer resistência do patógeno a esses produtos (KURAMAE-IZIOKA et al, 1997). Dessa forma, o uso de clones resistentes à PFC torna-se desejável (FEICHTENBERGER et al, 2005).…”

“…Contudo, as plantas do clone "IAC 5-1" apresentaram maior porcentagem de cálices retidos, indicando maior suscetibilidade à doença (Tabela 1). A presença de cálices retidos na planta não necessariamente está relacionada aos danos que esta doença possa ocasionar, pois, infecções que ocorrem em flores antes da antese podem causar a queda de flores juntamente com os cálices (SILVA-JUNIOR et al, 2014). Além disso, a quantidade de frutos fixados em relação ao número total de flores formadas é naturalmente baixo em citros (AGUSTÍ, 2003), podendo haver clones cuja capacidade de fixação de frutos compense eventuais perdas causadas pela doença.…”

Fungicide sensitivity and spatial and temporal dynamics of <i>Botrytis cinerea</i> and <i>Colletotrichum</i> spp. in conventional and organic strawberry fields

“…causing citrus postbloom fruit drop, and the bacteria Xanthomonas citri subsp. citri, causal agent of citrus canker, before the introduction of the citrus leaf miner), may cause epidemics that present an aggregated distribution pattern for diseased plants, given that the probability of a plant to be infected is higher for plants that are closer to the source of inoculum (BERGAMIN FILHO et al, 2000;SILVA-JUNIOR et al, 2014). Aggregation pattern was also observed in our studies for Botrytis fruit rot with symptomatic fruit within a plant, suggesting that nearby fruit and plants present higher chances of becoming diseased.…”

Desempenho horticultural de laranjeiras doces de meia-estação sobre tangerineira 'Sunki'

“…A distribuição das árvores doentes e as elevadas taxas de progresso da PFD indicam uma dispersão eficiente. Essa eficiência pode estar relacionada a um mecanismo alternativo para a disseminação do inóculo e pesquisas são necessárias para determinar se os insetos também são os vetores responsáveis pela disseminação da PFD a longa distância (SILVA JUNIOR et al, 2014b).…”