African Journal of
Agricultural Research

  • Abbreviation: Afr. J. Agric. Res.
  • Language: English
  • ISSN: 1991-637X
  • DOI: 10.5897/AJAR
  • Start Year: 2006
  • Published Articles: 6693

Full Length Research Paper

Diagrammatic scale for blister spot in leaves of coffee tree

Marcelo Loran de Oliveira Freitas*
  • Marcelo Loran de Oliveira Freitas*
  • Departamento de Fitopatologia, Universidade Federal de Lavras, Lavras, MG, Brazil.
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Mario Sobral de Abreu
  • Mario Sobral de Abreu
  • Departamento de Fitopatologia, Universidade Federal de Lavras, Lavras, MG, Brazil.
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Marcelo Loran de Oliveira Freitas
  • Marcelo Loran de Oliveira Freitas
  • Departamento de Fitopatologia, Universidade Federal de Lavras, Lavras, MG, Brazil.
  • Google Scholar
Jhonata Lemos da Silva
  • Jhonata Lemos da Silva
  • Instituto Federal de Educação, Ciência e Tecnologia do Amazonas, Humaitá, AM, Brazil.
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Mario Sobral de Abreu
  • Mario Sobral de Abreu
  • Departamento de Fitopatologia, Universidade Federal de Lavras, Lavras, MG, Brazil.
  • Google Scholar


  •  Received: 19 December 2014
  •  Accepted: 15 April 2015
  •  Published: 07 May 2015

Abstract

Blister Spot is a disease transmitted through seeds. This characteristic of the disease reveals the studies of severity can offer more replies than the studies of incidence. Due to the inexistence of standardized for visual quantification of the Blister Spot’s severity, the aim of this work was to build up and validate a diagrammatic scale for evaluating the severity of Blister Spot in coffee tree. Leaves in the field were collected with different intensities of symptoms disease, and electronically determined the real severity. Based on the frequency distribution of the severity values, and according to the law of visual stimulus of Weber-Fechner, the maximum and minimum limits, and the intermediate levels of the scale were defined. The validation was realized by eight evaluators that estimated the severity in 50 leaves with different intensities of symptoms. An evaluation without the aid of the diagrammatic scale was realized, and two others with its use, having intervals of seven days. The accuracy, precision, repeatability and reproducibility of the estimate were evaluated. The developed scale shows seven 0 (0%), 1 (0.1-3%), 2 (3.1-6%), 3 (6.1-12%), 4 (12.1-25%) and5 (≥25.1%). Using the scale proposed, the evaluators presented better levels of accurancy, precision, reproducibility and repeatability in the estimate, once compared to the evaluators who did not use the diagrammatic scale. The diagrammatic scale was adjusted to aid in the visual estimate of the severity of the Blister Spot in coffee leaves

 

Key words: Coffea arabica, Colletotrichum gloeosporioides, pathometry.