Molds and cankers can quickly decimate a crop. Control can be difficult, but many practical considerations and cultural practices can greatly reduce outbreaks. Care in choosing both the site and design of production greenhouses should be a grower’s first consideration. A good start to managing pathogens is to optimize light and ventilation with a north/south placement and use materials that are easily sanitized. Maintaining proper temperature and humidity, ensuring optimal air circulation, keeping plant foliage dry, watering early in the morning, and stringent sanitation practices are also key to reducing pathogenic outbreaks such as grey mold and powdery mildew.
Start out on the right foot
Certain poly coverings can route condensation to the eaves. This may also be achieved with the application of a surfactant, thus reducing condensation droplets and contaminants that may fall onto plants. Some coverings that filter UV may help inhibit some pathogens. The use of shade curtain systems to reduce temperature inversion in the morning can help reduce condensation. A heating/ventilation cycle before sunrise can also reduce condensation from temperature inversion. Nonporous materials are more easily sanitized and should be a consideration in facility design.
Keep it dry
Keep water off of foliage and maintain good air circulation. Make sure that plants are not crowded, which will increase airflow where it is needed and reduce senescence. Maintain relative humidity below 50% and reduce irrigation to a minimum throughout the bloom to help ensure crop success.
Keep it clean
Sanitize everything. Sanitize the whole house between crops. Sanitize tools between use. Keep crops segregated to avoid cross contamination. Keep the house clear of litter and do not store waste inside the greenhouse. Prune plants regularly. Remove symptomatic plants and dispose of them, including substrate, immediately. Sterilize all containers before reuse.
Consider chemical and biological controls on a case-by-case basis. Generally speaking, few, if any, are great options for consumable crops.