How can I manage diseases in greenhouse herb production?

Answer: The most common diseases in greenhouse herb production are fungal diseases, including botrytis, damping-off, powdery mildew, and root rots. Vascular wilts are also common in herbs. These diseases can cause tremendous plant loss in just a few days if conditions are favorable and no control is in place. Open beds, raised beds, and temporary structures such as hoop houses can prevent disease buildup from year to year due to weather exposure, whereas greenhouses?with poor air circulation, dense plant canopies, plant crowding, and high humidity? can increase the incidence of disease.
Preventing disease buildup in greenhouses is very similar to the cultural control part of the IPM plan mentioned earlier to control pests: i.e., remove diseased plants, keep walkways and exterior areas weed-free, keep equipment clean, and maintain good air circulation through the structure. In addition to these basics, there are additional practices that may help:
Use irrigation techniques that minimize leaf wetness. Avoid late afternoon and nighttime irrigation.For herbs grown in ground beds, rotate plant families. Use only clean stock for propagation. Control insects that vector disease.
You’ll benefit from reading the ATTRA publication Herbs: Organic Greenhouse Production. This publication discusses various marketing channels for organic herbs and assesses the economic factors to consider for small-scale organic greenhouse production of fresh-cut herbs. It also addresses production methods, including potential for hydroponic production.