Abstract

CRISTIANE-DELMADI, Leila; PIERI, Cristiane de; SANDER-PORCENA, Alex  and  LUIZ-FURTADO, Edson. Diagramatic scale for quantification of rust severity in teak leaves. Rev. mex. fitopatol [online]. 2018, vol.36, n.2, pp.331-341. ISSN 2007-8080.  https://doi.org/10.18781/r.mex.fit.1708-5.

Teak (Tectona grandis) rust, caused by the fungus Olivea tectonae, has been present in several regions of Brazil in severe cases that lead to the premature fall of the leaves and even the death of the plant. However, there is still no standard method for assessment of disease severity in the field. The objective of this study was to develop and validate a diagrammatic scale to quantify the rust severity in leaves of teak. The diagrammatic scale was developed based on disease severity encompassing 0, 2.5, 5, 10, 20, 40 and 80% of the leaf area with rust symptom. The scale was validated by 10 raters, who analyzed 50 leaves with a range of disease severity, without and with diagrammatic scale as an assessment aid. The raters presented differences in the perception of the severity levels of the disease. With the adoption of the diagrammatic scale all the raters improved the accuracy of the estimates, there was a reduction in the absolute errors and good estimates of repeatability. The proposed diagrammatic scale is suitable for the evaluation of the rust severity in teak leaves, being able to provide accuracy and repeatability of estimates.

Keywords : Tectona grandis; Olivea tectonae; disease assessment.

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