Which condition is NOT favorable to the development of seedling diseases?

• A. Use of soilless growing medium
• B. Excessive soil moisture
• C. Overcrowded seedling flats
• D. Low soil temperatures before germination

Answer: (A)

Seedling diseases take hold when environmental conditions give pathogens and stressed seedlings an edge. Using a soilless growing medium helps prevent these diseases because such media are typically sterile or clean and drain well, giving the roots strong oxygen access and reducing the presence of soil-borne pathogens that cause damping-off. In contrast, excessive moisture creates the wet, oxygen-poor conditions that many seedling pathogens, like Pythium, thrive in; overcrowded flats trap humidity and reduce airflow, increasing leaf and stem moisture and the chance for spread; and low soil temperatures before germination slow seedling growth and keep seedlings vulnerable as pathogens attack vulnerable tissue. So, the use of a soilless medium is not favorable to the development of seedling diseases, while the other conditions promote them.