How do you prevent mold in high-humidity greenhouses?
Written by
Benjamin Miller
Reviewed by
Prof. Samuel Fitzgerald, Ph.D.In greenhouses subject to high humidity, preventing mold involves proactive strategies that preserve plant health while controlling moisture levels. Generally, when relative humidity exceeds 70% and air circulation is poor, mold appears. It is essential to balance humidity levels with carefully controlled environments and effective sanitation methods to protect crops.
Vapor Pressure Deficit Management
- Maintain 0.8-1.5 kPa VPD for optimal transpiration
- Calculate using temperature and humidity sensors
- Prevents moisture accumulation on plant surfaces
- Automated systems adjust conditions before mold develops
Strategic Airflow Systems
- Horizontal airflow fans create uniform air movement
- Position fans to avoid dead zones near corners
- Maintain 0.3-0.5 m/s air speed at plant canopy
- Continuous circulation prevents stagnant humid pockets
Sanitation Protocols
- Disinfect surfaces weekly with hydrogen peroxide solutions
- Sterilize tools between different crop sections
- Remove plant debris immediately to eliminate spore sources
- Install footbaths at greenhouse entry points
Vapor Pressure Deficit control prevents mold from forming by managing moisture levels in a plant's environment. For optimal plant transpiration, the VPD should be maintained at 0.8 to 1.5 kPa. This keeps an optimum moisture balance, hence no guttation droplets form, on which the mold spores depend. By monitoring leaf-surface temperatures, therefore, automated VPD regulating systems can maintain them at the requisite levels.
Air circulation systems must eliminate stagnant areas. Place horizontal airflow fans to cover the entire area of each plant canopy. Regulate airflow to maintain a steady velocity of 0.3 m/s (1.0 feet/second) across all surfaces. This will prevent humidity stratification, where the mold grows unnoticed.
Dehumidification technology efficiently removes excessive moisture. Modern systems remove 5-10 liters per hour per 100 m² and have superior control to maintain humidity within 2% of the set point. When possible, combine dehumidification with ventilation during cooler weather to help reduce energy consumption.
Sanitation safeguards against mold outbreaks. Disinfect surfaces weekly with food-grade hydrogen peroxide. Remove plant debris as you find it. Sterilize the tools when you move between different areas in the greenhouse to prevent contamination.
Integrated systems provide comprehensive mold protection. Combine VPD management with air circulation and dehumidification to optimize indoor air quality. Add regular sanitation routines. This approach reduces mold incidents by over 90% in high-humidity environments.
Read the full article: Greenhouse Climate Control: Growth & Efficiency
