Horsfall-Barratt scale

The Horsfall-Barratt scale Citation
last1 = Horsfall | First1 = J. G.
last2 = Barratt | First2 = R. W.
title = An Improved Grading System for Measuring Plant Disease
journal = Phytopathology
year = 1945] is a system used in plant pathology to assess plant diseases where each plant is assigned a numerical value according to the percentage of leaf area showing disease symptoms. The Horsfall-Barratt scale was designed to compensate for human error in estimating the amount of disease present. The scale is as follows:

The scale is often used in modified form with index values from 0-11 or with different numbers of index points.

References