Greenhouse and Nursery - Cultural Practices to Prevent Disease

The following are some cultural practices to consider to prevent disease in greenhouse or nursery production.

• Checking Planting Depth: Follow the planting depth recommended for each species--Planting plants too deeply predisposes them to crown rot, and can result prevent flowering; Planting too shallowly can cause them to topple during watering and can lead to root drying and added stress.
• Adequately Spacing Plants: Crowded plants prevent good air movement, which promotes foliar diseases. Close spacing also causes plants to compete with each other for sunlight and nutrients. With vigorous plants, the canopy that is created around the plant favors downy mildews, Rhizoctonia, Botrytis, and Phytophthora aerial blights.
• The right media: There are dozens of greenhouse and nursery media mixes available. A simple rule of thumb to picking out the right media is that larger rooted plants require a larger size mix (larger sized media components). This facilitates drainage and reduces root rot.
• Appropriate Watering: With the tremendous diversity of greenhouse and nursery plants available, it is difficult to generalize about watering needs. However, it is important to remember that water is for the roots. Avoid overhead irrigation if possible, and when overhead watering, water plants in the morning so foliage can dry before nighttime. Monitor media moisture and do not overwater plants. This is important for media types that hold higher quantities of water. For root rot susceptible plants, choose a media that drains freely.
• Proper Fertilizing: Fertilizer should only be applied to achieve desired growth or when nutrient deficiencies are noted, such as yellowing (chlorosis). Too much fertilizer, especially nitrogen, predisposes plants to disease.
• Soil Contact: If at all possible, grow plants so that they are off the ground and not in contact with the soil to avoid potential infection from soil borne diseases.

Adapted in part from Plant Pathology and the Greenhouse by Janna Beckerman, Assistant Professor, Department of Botany and Pant Pathology, Purdue University