| Crop | Temp (°C) | RH (%) | Wetness (h) | Rain (mm) | Canopy | Irrigation | Severity | Risk score | Rate (%/day) | Band |
|---|---|---|---|---|---|---|---|---|---|---|
| Rose | 19 | 92 | 14 | 3 | Dense | Sprinkler | 3 | 78.4 | 1.87 | High |
| Bean | 26 | 70 | 6 | 0 | Medium | Drip | 1 | 34.9 | 0.63 | Moderate |
| Wheat | 16 | 88 | 12 | 5 | Medium | Furrow | 2 | 66.1 | 1.29 | High |
This calculator converts weather and management signals into a 0–100 rust risk score, then estimates daily leaf-area loss.
base = 0.22·T + 0.20·RH + 0.20·Wet + 0.08·Rain + 0.05·Wind + 0.10·History + 0.07·Canopy + 0.04·Irrigation + 0.04·(1−Resistance)
rate(%/day) = (0.10 + 1.90·score/100) × (0.55 + 0.70·severity/5)
- T peaks near 20°C and fades outside the comfort range.
- Wet rises with leaf wetness hours (dew, fog, splash).
- Protection decays over about 14 days after spraying.
- Banding: Low < 30, Moderate 30–59, High 60–79, Severe ≥ 80.
- Measure today’s temperature, humidity, and recent rainfall.
- Estimate leaf wetness hours from dew, fog, or irrigation.
- Set canopy density and irrigation type to match your bed.
- Slide severity based on visible rust pustules and spotting.
- Press Calculate to view results above the form.
- Download CSV or PDF to save the estimate for records.
Risk scoring inputs and ranges
The calculator converts daily conditions into a 0–100 rust pressure score. Temperature is most favorable near 20°C and fades outside 5–35°C. Relative humidity contributes strongly above 60% and approaches peak impact near 95%. Leaf wetness scales from 0 to 16 hours, capturing dew, fog, and irrigation splash. Rainfall increases risk up to about 20 mm, reflecting spore movement and canopy splash. Wind is treated as a dispersal and drying balance, with moderate breezes contributing more than calm air or very strong winds that dry leaves quickly. Together, these inputs describe daily infection opportunity.
Management factors that shift outcomes
Local history raises baseline pressure because inoculum may persist on residue and hosts. Canopy density is scored from 1 to 3, where dense growth holds moisture longer and slows drying. Irrigation type matters: drip and soaker systems reduce wet leaves compared with overhead sprinklers. Variety resistance lowers susceptibility, so a high-resistance plant can remain in a lower band under the same weather.
Protection decay and scouting influence
If protection is enabled, effectiveness is treated as a multiplier that decays over roughly 14 days. A fresh 80% treatment reduces the score sharply, while protection approaches neutral as days increase. Scouting interval adds a small stabilizing factor: frequent checks reduce missed outbreaks and help prevent severity rising unnoticed.
Rust rate estimate and band meaning
After scoring, the tool estimates daily leaf-area loss in percent per day. The rate rises with score and is scaled by the field severity slider (0–5). Bands are set for clarity: Low under 30, Moderate 30–59, High 60–79, and Severe 80 or above. Use the band to prioritize actions and timing.
Using results for decisions and records
Pair the estimate with visible symptoms and local guidance. When scores are Moderate or higher, adjust watering time, increase airflow, and remove infected leaves. Save outputs as CSV or PDF to compare weeks, track treatment timing, and relate humidity and wetness changes to rust progression for better planning.
FAQs
How accurate is the risk score?
It is an estimate that standardizes common rust drivers. Use it to compare days and prioritize scouting, not as a laboratory diagnosis. Adjust inputs with real observations for best usefulness.
What should I use for leaf wetness hours?
Add hours when leaves stayed visibly damp from dew, fog, rain, or irrigation splash. If unsure, estimate from sunrise to when foliage dried, then refine after a few days of checking.
Why does overhead irrigation increase the score?
Overhead watering extends wetness and splashes spores across leaves. Drip or soaker systems keep foliage drier, shortening infection windows and lowering daily pressure in most gardens.
How does protection decay work here?
Effectiveness reduces risk most right after application and fades toward neutral over about 14 days. Enter the days since spray and a realistic field effectiveness to reflect coverage and weathering.
What does the rust rate (%/day) mean?
It approximates how fast leaf area could be affected each day under current pressure and severity. Higher rates suggest faster spread and a need for quicker sanitation, airflow improvements, or labeled treatments.
Can I export multiple runs?
CSV and PDF exports store the latest saved run in your session. For multiple dates, download after each calculation or copy results into a log sheet, then compare trends across weeks.