Data/hora: 02/06/2024 08:48:56

Biblioteca(s): | Embrapa Mandioca e Fruticultura.
Data corrente: | 15/12/2010
Data da última atualização: | 19/01/2011
Autoria: | DESIMONE, E. R.; LARANJEIRA F. F.; NERI, F. M.; CUNNIFFE, N. J.; GILLIGAN, C. A.
Afiliação: | Erik R. DeSimone, UCLES; FRANCISCO FERRAZ LARANJEIRA BARBOSA, CNPMF; Franco Maria Neri, UCLES; Nik J. Cunniffe, UCLES; Chris A. Gilligan, UCLES.
Título: | Modelling spread and control of Bahia Bark Scaling of Citrus.
Ano de publicação: | 2010
Fonte/Imprenta: | In: CONFERENCE INTERNATIONAL ORGANIZATION CITRUS VIROLOGISTS, 18., Campinas, SP, 2010. Proceedings... Campinas: IOCV, 2010. 1 CD-ROM.
Idioma: | Português

Notas:

049.PSO.
Publicado também em: Citrus Research & Technology, Cordeirópolis, v. 31, Suplemento, 2010

Conteúdo: | Bahia bark scaling of citrus (BBSC) affects most citrus species and varieties, but is especially severe on grapefruits. It was first recorded in the 1960?s in the state of Bahia, Brazil, and is restricted to two northeastern states of that country. BBSC symptoms include a darkening and thickening of the bark leading to scaling lesions on trunk and branches; young branches exhibiting dieback; and significant gum extrusion. Symptoms resemble those of Citrus Psorosis A, but accumulated data indicate BBSC is a distinct disease, although its etiology remains unknown. The only epidemiological study about BBSC showed that it is polyetic, naturally transmitted and its progress and spread is consistent with transmission by an insect of limited dispersion ability. The combination of a long incubation period, no biological nor molecular test to detect the putative pathogen, and the polyetic nature of the epidemic, present difficulties for field experimentation to analyze and predict disease dynamics and effectiveness of control. Hence modelling can help to screen likely candidates for experimental investigation and quantification. A flexible, spatially-explicit, stochastic SEIDR model was used to simulate BBSC progress and spread, after model fitting to experimental disease spread data using MCMC techniques. All simulations were run on a virtual grove reflecting standard citrus cultivation practices in Bahia, Brazil, consisting of 14 rows each containing 120 trees with a 6mx4m spacing between trees. Three control measures to reduce the spread of BBSC within the grove were modelled: sanitation of new plantings, intercropping non-host plants, and roguing infectious trees. Sanitation effort was defined as a percentage of disease-free trees in a newly planted grove. The maximum effort considered was 99.875% (2 trees initially infected out of 1680 total trees), leading to a mean of 235 months until unprofitability. With sanitation effort of 99.45%, the productive lifetime was 120 months. When only 1% of the newly planted trees were infectious (99% sanitation effort), the productive lifetime of the grove was under 100 months. The effects of cropping distances were quantified by measuring the number of infectious plants over 15 years. In the 10x10m grove, 3% of the trees were infected after 15 years; corresponding to an increase of 2%, as the initial condition was 1% of infected trees; however, in the 2x2m grove 100% of the trees were infected after 15 years. Examining the number of uninfected trees after 15 years as a function of tree density demonstrated the trade-off between disease-induced loss of yield and lower productivity from low density planting. The maximum median number of productive trees occurred at a planting density of 200 trees per hectare (~7mx7m spacing). Roguing was modelled by setting the detection efficacy of the survey at 60%, allowing for some of the infected plants to escape removal, and the epidemic to continue. Eight survey intervals were used (1, 3, 6, 8,10, 12, 15, 24 months) and control success was assessed by examining the mean number of susceptible trees remaining after 30 years. The probability of success was maximum for roguing intervals of 1 or 3 months, dropping to 0.42 for interval of 12 months. Currently, there is no effort in Bahia to remove symptomatic trees (putatively infectious). Also, planting densities are usually high because the farms are small and there is a number of pieces of evidence that sanitation procedures are not 100% efficient. The simulation results show that a combined strategy of strong sanitation effort, lower planting densities and roguing could lead to a very good control of BBSC. In the optimal 7m x 7m spacing we have identified, intercrops such as passionfruit, guava or barbados cherry are possible, contributing to a more efficient land use.
Palavras-Chave: | Bahia Bark Scaling of Citrus.
Thesagro: | Fruta Cítrica.
Categoria do assunto: | X Pesquisa, Tecnologia e Engenharia
Registro original: | Embrapa Mandioca e Fruticultura (CNPMF)
Exemplares: | CNPMF - (27067-1) - UPC - RA - PP - CD2010.011 -  - 2010.011 - PCT