COMPARISON AND VALIDATION OF DIAGRAMMATIC SCALES FOR BROWN EYE SPOTS IN COFFEE TREE LEAVES

A diagrammatic scale with six levels (0.1-3.0; 3.1-6.0; 6.1-12.0; 12.1-18.0; 18.1-30.0; 30.1-49.0%) was developed, compared, and evaluated along with two other scales to measure the severity of brown eye spots in coffee trees leaves. The scale was designed based on two others already in use in order to increase the efficiency of evaluation and for estimation values to approach as close as possible to their actual values. Two evaluations were performed using each of the three diagrammatic scales and one was performed without a diagrammatic scale, in seven day intervals. Using the proposed scale, the evaluators demonstrated better precision levels, accuracy, reproducibility, and repeatability in the estimations, when compared to the evaluators who did not use the diagrammatic scale, or who used existing scales. The proposed diagrammatic scale provided a reliable estimation to evaluate brown eye spot severity on coffee tree leaves.