Cercospora leaf spot of sweet pepper caused by the fungus Cercospora capsici is an important disease occurring in tropical conditions. Due to the inexistence of standard methods to quantify this disease in field conditions, a diagrammatic key including the levels 1.5, 3.5, 8.0,16.5, 31.0 and 50.0% of diseased leaf area was elaborated and tested for accuracy, precision and reproducibility to estimate Cercospora leaf spot severity without and with using the key. The diagrammatic key was validated by 13 raters with and without using the key, using 50 leaves with different levels of severity previously measured by the software AutoCAD®. Two evaluations were performed with the key at 7-day intervals when the same raters visually estimated different sequences of the same leaves. The accuracy and precision of each rater were determined by simple linear regression between actual and estimated severity. Without the key, eight raters overestimated disease severity. With the key raters obtained better levels of accuracy and precision, however four of them tended to overestimate the severity with absolute errors concentrated below 10%. Raters had good repeatability and high reproducibility in estimating disease severity by using the key when it was not used. The proposed diagrammatic key is suitable for evaluation of sweet pepper Cercospora leaf spot severity.
Capsicum annuun; Cercospora capsici; leaf disease; pathometry