Disease Severity Index Calculator
Compute foliar disease severity index from visual assessments using the standard 0-5 Horsfall-Barratt scale.
Inputs
Results
Disease Severity Index (%)
20.57
Disease incidence (%)
60%
How to Use This Calculator
- Enter Class 0 plants (0% affected), Class 1 plants (1-10% affected), and Class 2 plants (11-25% affected).
- Set Class 3 plants (26-50% affected), Class 4 plants (51-75% affected), and Class 5 plants (76-100% affected).
- Review Disease Severity Index (%) and Disease incidence (%) (%).
- Use Mean severity (%) and Total plants assessed to inform your decision.
How the result changes with Class 0 plants (0% affected)
| Class 0 plants (0% affected) | Disease Severity Index (%) | Disease incidence (%) |
|---|---|---|
| 1,000 | 1 | 2.91% |
| 3,500 | 0.29 | 0.85% |
| 6,500 | 0.16 | 0.46% |
| 9,000 | 0.11 | 0.33% |
What each input means
- Class 0 plants (0% affected)
- Number of plants with no visible disease symptoms.
- Class 1 plants (1-10% affected)
- Plants with 1-10% tissue affected.
- Class 2 plants (11-25% affected)
- Plants with 11-25% tissue affected.
- Class 3 plants (26-50% affected)
- Plants with 26-50% tissue affected.
- Class 4 plants (51-75% affected)
- Plants with 51-75% tissue affected.
- Class 5 plants (76-100% affected)
- Plants with 76-100% tissue affected.
What each result means
- Disease Severity Index (%)
- Overall disease severity index on a 0-100 scale (McKinney formula).
- Mean severity (%)
- Average percentage of tissue affected per plant.
- Disease incidence (%)
- Percentage of plants showing any disease symptoms.
- Total plants assessed
- Sum of all plants across all severity classes.
- Diseased plants
- Number of plants with disease symptoms (class 1-5).
- Severity rating (1-4)
- 1 = Low (DSI ≤10), 2 = Moderate (11-30), 3 = High (31-50), 4 = Severe (>50).
Related Calculators
The questions that sit next to this one — chosen by subject, including calculators filed under a different category.
Disease Forecasting Model Calculator
Predict plant disease infection risk from weather conditions, host susceptibility, and inoculum pressure using DSV-based forecasting.
Pest MonitoringDegree Day Calculator
Accumulated degree days from daily temperature data using the single-sine method for predicting pest development stages.
Pest MonitoringIPM Score Calculator
Evaluate your Integrated Pest Management adoption level across six key pillars with a weighted composite score.
GastroenterologyIBD Activity Score Calculator
Calculate Crohn's Disease Activity Index (CDAI) from symptoms, lab values, and physical exam findings. Classifies remission, mild, moderate, and severe disease.
More in Home, Garden & Maintenance.