Pathogen Pressure Forecast.
Pathogen Pressure Forecast
Environmental conditions favor different pathogens. This tool flags which are most likely given yours.
How this works
Most agricultural pathogens have well-documented environmental drivers. Botrytis (gray mold) thrives at high humidity and cool temperatures with still air. Spider mites multiply in hot, dry, low-airflow conditions. Pythium colonizes warm, oxygen-poor root zones. The conditions don't cause disease — pathogens still need to be present — but they create the windows in which infections take hold.
The pressure index above is a 0-1 score combining the environmental drivers for each pathogen. It is advisory, not diagnostic. A high botrytis score doesn't mean you have botrytis; it means conditions favor it if spores are present. Inspecting plants and adjusting environment proactively is the use case.
Pathogen drivers
| Pathogen | Loves | Hates |
|---|---|---|
| Botrytis (gray mold) | RH > 60%, temp 60-70°F, still air, leaf wetness | Low RH, strong airflow, dry leaves |
| Powdery mildew | RH 55-90%, moderate temp, still air, leaf wetness | Direct UV, very low RH, strong airflow |
| Spider mites | Temp > 80°F, RH < 40%, low airflow, dry conditions | High RH (mite predators thrive there too) |
| Russet mites | Temp 70-85°F, RH moderate, dense canopy | (cannabis-specific; harder to spot) |
| Pythium (root rot) | Root temp > 75°F, low DO, waterlogged substrate | Cool roots, well-oxygenated water |
| Fusarium | High root temp, high RH, plant stress | Cool roots, healthy plants |
| Septoria leaf spot | Leaf wetness, temp 60-80°F, high RH | Dry leaves, low RH |
| Damping-off (seedling) | High RH, cold soil, sterile substrate, weak airflow | Warm soil, beneficial microbes, airflow |
| Aphids | Spring temps, high N tissue, weak predators | Cold; dry; predator-friendly polyculture |
| Whitefly | Warm + high N tissue + sheltered conditions | Cold; predator-friendly habitats |
Severity reference
- Pressure 0.00-0.30: Low risk. Conditions don't favor this pathogen. Standard monitoring.
- Pressure 0.30-0.60: Moderate. One or two factors are favorable. Inspect; consider light prevention.
- Pressure 0.60-0.85: High. Multiple drivers aligned. Active prevention warranted (airflow, RH adjustment, foliar drench).
- Pressure > 0.85: Critical. Conditions are textbook for this pathogen. Aggressive intervention; environmental adjustment is urgent.
Most common interventions
- Lower RH — fastest path to reducing botrytis, powdery mildew, septoria pressure. Dehumidifier capacity often the limit.
- Increase airflow — moves boundary-layer humidity off leaf surfaces; mechanical disruption of spore landing.
- Eliminate leaf wetness — water early in photoperiod; avoid foliar applications close to dark; ensure good drying time.
- Cool root zone — reservoir chillers for hydroponic; insulate / raise pots in soil-based for outdoor heat events.
- Oxygenate root zone — air pump in DWC; moisture cycling in coco/peat to allow drying back.
- Beneficial inoculation — Trichoderma harzianum out-competes Pythium; Bacillus subtilis suppresses powdery mildew; predatory mites for spider mites.
Free under CC BY 4.0. Cite as "OAT Pathogen Pressure Forecast (openagriculturetechnology.com)". Pressure indices synthesized from peer-reviewed plant pathology literature.