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Cruz das Almas, Brazil

Silva S.X.B.,Diretoria de Defesa Vegetal | Soares A.C.F.,Federal University of Reconcavo da Bahia | Almeida D.O.,Federal University of Reconcavo da Bahia | Santos-Filho H.P.,Phytopathology Laboratory | Laranjeira F.F.,Phytopathology Laboratory
Annals of Applied Biology | Year: 2015

Recôncavo Baiano is an area favourable for the occurrence of citrus greasy spot (CGS) (Mycosphaerella citri), but there has been no study of this pathosystem in Brazil. This work aimed to characterise the temporal patterns of CGS-induced defoliation in sweet orange cultivars 'Bahia' (Washington Navel) and 'Pêra'. Temperature, rainfall and relative humidity were recorded, as well as weekly defoliation (fallen leaves/canopy m2 or m3). Considering the mean of fallen leaves per canopy m2, and mean canopy area, the total annual defoliation was estimated to be around 32 000 leaves per plant for 'Bahia' and 18 500 for 'Pêra' sweet orange. Spectral density analysis showed that defoliation has a 5-week-long main cycle for both cultivars. The proportion of symptomatic fallen leaves was never below 0.97. The monthly number of fallen leaves per canopy area was positively correlated with the mean CGS incidence on leaves. Defoliation was significant, resulting in a low leaf density throughout the year. Many defoliation cycles and the very high proportion of symptomatic fallen leaves assure a constant inoculum supply. Based on these results, CGS cannot be considered a minor disease, at least in Recôncavo Baiano. © 2015 Association of Applied Biologists. Source

Ten Hoopen G.M.,British Petroleum | Ten Hoopen G.M.,CIRAD - Agricultural Research for Development | Ten Hoopen G.M.,Phytopathology Laboratory | Deberdt P.,British Petroleum | And 5 more authors.
Annals of Applied Biology | Year: 2012

Cacao trees are affected by diseases that attack either their vegetative parts, their fruits or both. In cacao pod diseases, several factors are involved in disease susceptibility, such as the fruiting cycle, fruit size, age, position on the tree and cacao genotype. To gain a clearer understanding of how these characteristics influence cacao pod diseases, four models describing pod growth in several cacao genotypes were evaluated. Three models used to estimate pod volume or surface area were also compared. Observed pod growth was of a sigmoid form and fitted best to the Richards model, well to the Logistic and Beta growth models, and least to the Gompertz model. Pod volume and probably pod surface area were best estimated using a prolate spheroid model. Pod growth models can help improve pod disease management and thereby cacao production. They can help to predict yield, as well as provide information for the timing and frequency of control operations. Information on pod size, surface area and susceptibility will help to improve dose transfer and spray deposit studies intended to optimise control efficiency. © 2012 Association of Applied Biologists. Source

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