A new diagrammatic scale for the assessment of northern corn leaf blight

A diagrammatic scale was developed to assess the severity of northern corn leaf blight (NCLB), which is caused by the fungus Setosphaeria turcica. The validation of this new scale in relation to accuracy and precision was carried out by eight evaluators who estimated the severity of the infection on maize leaves showing NCLB symptoms, with and without the use of the scale. The new scale was also evaluated in relation to a published NCLB assessment scale. The precision and accuracy of the assessments were determined by linear regression, relating the estimated versus actual severity of NCLB as determined by image analysis. Using the new diagrammatic scale, evaluators were able to improve the precision and accuracy of NCLB assessments. (C) 2013 Elsevier Ltd. All rights reserved.