Elaboração e validação de escala diagramática para avaliação da severidade do mofo cinzento em mamoneira

Abstract

ABSTRACT Elaboration and validation of diagrammatic scale to evaluate gray mold severity in castor bean A diagrammatic scale was developed to standardize assessment of gray mold in castor bean bunches, caused by Amphobotrys ricini. Both the maximum and minimum limits of disease severity observed in the field were considered, and the intermediate values progressed by logarithmic increments, representing: 3, 5, 8, 12, 25, 50, 76, 86, 94 and 100% of necrotic area. The scale was validated by 10 raters in three phases: first the raters estimated the severity in 40 photographs without using the scale. In the second and third phases, the same raters estimated the severity in the photographs but with different sequences, with a seven-day interval between assessments. Accuracy, precision, repeatability and reproducibility of estimates were determined by linear regression, relating assessments performed by raters using the scale to actual severity, and relating the results between two assessments using the scale. Assessments with the diagrammatic scale were precise and accurate, the absolute errors were lower than the acceptable limits and the raters exhibited good repetition of estimates. The proposed diagrammatic scale proved to be adequate for severity assessments of gray mold in castor bean.