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.
Highlights
The diagrammatic scale was adjusted to aid in the visual estimate of the severity of the Blister Spot in coffee leaves
The Blister Spot is a disease of the coffee tree, whose causal agent found in Brazil, is the fungus Colletotrichum gloeosporioides PENZ. (Miranda, 2003)
The diagrammatic scale proposed in this article like others, were constructed defining the intervals according to the law of “Weber-Fechner” (Custódio et al, 2011; Salgado et al, 2009), without following the same intervals of severity proposed by Horsfall and Barratt (1945) due to the disease’s peculiarity
Summary
The Blister Spot is a disease of the coffee tree, whose causal agent found in Brazil, is the fungus Colletotrichum gloeosporioides PENZ. (Miranda, 2003). The Blister Spot is a disease of the coffee tree, whose causal agent found in Brazil, is the fungus Colletotrichum gloeosporioides PENZ. Its symptoms are light green spots with less brightness in relation to asymptomatic areas, having oily looking, ranging from 2 to 10 mm diameter. With the progress of the disease, the spots show the necrotic, which can coalesce and result in necrosis of bigger areas and leaves fall. Besides these symptoms, the pathogenic can be associated with the mummifications and fruits’ abscision and the wilt and dry of the branch (Pozza et al, 2010). The season of higher intensity of these symptoms is between October and February, period of higher rainfall index (Ferreira et al, 2009a).
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