Pest Infestation Severity Score Calculator
Calculate a composite Pest Infestation Severity Score (PISS) using population density, affected area, crop damage, pest mobility, and proximity to the economic injury level (EIL). Scores range from 0 (no infestation) to 100 (catastrophic).
Fill in all fields and click Calculate.
Formula
PISS = 100 × [ 0.35·SEIL + 0.25·Sarea + 0.30·Sdamage + 0.10·Smobility ]
Where each sub-score is normalised to [0, 1]:
- SEIL = min(density / EIL, 1) — how close the pest density is to the Economic Injury Level.
- Sarea = infested area / total crop area — proportion of the crop that is affected.
- Sdamage = observed damage (%) / 100 — fraction of crop visibly damaged.
- Smobility = (mobility index − 1) / 4 — normalised pest spread potential (1 = sedentary, 5 = highly mobile).
Weights (0.35, 0.25, 0.30, 0.10) reflect the relative agronomic importance of each factor and sum to 1.00.
Severity bands: 0–19 Negligible | 20–39 Low | 40–59 Moderate | 60–79 High | 80–100 Catastrophic.
Assumptions & References
- The Economic Injury Level (EIL) is the pest density at which crop losses equal the cost of control (Stern et al., 1959, Hilgardia).
- Weights are based on Integrated Pest Management (IPM) prioritisation frameworks (Pedigo & Rice, 2009, Entomology and Pest Management, 6th ed.).
- The mobility index is a qualitative 1–5 scale: 1 = soil-bound/sedentary, 3 = moderate dispersal, 5 = winged/highly migratory pests.
- Crop damage percentage should be assessed using standardised field scouting protocols (FAO, 2016, Integrated Pest Management).
- The EIL Proximity sub-score is capped at 1.0; densities above the EIL do not further increase this sub-score but trigger the EIL warning.
- This calculator provides a decision-support estimate. Always consult a certified agronomist or extension service for site-specific management decisions.