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The Horsfall-Barratt scale [1] 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:
Index | Percent Affected |
---|---|
1 | 0 |
2 | 0 to 3 |
3 | 3 to 6 |
4 | 6 to 12 |
5 | 12 to 25 |
6 | 25 to 50 |
7 | 50 to 75 |
8 | 75 to 87 |
9 | 87 to 94 |
10 | 94 to 97 |
11 | 97 to 100 |
12 | 100 |
The scale is often used in modified form with index values from 0–11 or with different numbers of index points.
References
- ^ Horsfall, J. G.; Barratt, R. W. (1945), "An Improved Grading System for Measuring Plant Disease", Phytopathology