A diagramatic scale with five levels of disease severity: 0.11; 0.51; 2.4; 10.2 and 34.9% was developed and validated to assess mycosphaerella blight in strawberry, caused by Mycosphaerella fragariae. The scale was developed considering the maximum and minimum limits of disease severity observed in the field and the intermediate values followed logarithmic increments according to the "Stimulus Law by Weber-Fechner". Initially the estimates of severity were performed without the use of the scale in 30 leaves with different levels of severity. Validation was carried out by seven appraisers, without previous pratice in assessing mycosphaerella blight in strawberry. Then, the appraisers estimated the severity of the same leaves previously assessed using the proposed diagrammatic scale. Assessments with the diagrammatic scale were of great precision for all raters and did not constitute systematic mistakes in over or underestimating the disease severity. The proposed diagrammatic scale was considered adequate to estimate mycospharela blight severity in strawberry.
Fragaria x ananassa Duch; Mycosphaerella fragariae; pathometry
