What is damping-off, which stage of plant growth does it affect, and how can it be prevented in seed starting trays?

• A. A pest insect that feeds on seeds; use insecticides
• B. A fungal disease that causes seedling collapse at the seedling stage; prevent with sterile starting mix, proper spacing, adequate air circulation, and controlled moisture
• C. A nutrient deficiency causing leaf curling; apply fertilizer
• D. A drought stress causing seed dormancy; water less

Answer: (B)

Damping-off is a fungal disease complex that attacks very young seedlings at the soil line, causing stems to soften, rot, and the plants to collapse just as they’re starting to grow. It typically shows up during the seedling stage in seed-starting trays, when you have many tiny plants crowded together in moist, warm, or poorly ventilated conditions. The harm comes from pathogens in the soil or starting mix, combined with moisture and air conditions that favor infection.

Prevention focuses on limiting those favorable conditions: use sterile, clean seed-starting mix and clean trays to reduce the amount of pathogen inoculum; avoid crowding so each seedling has space and airflow; promote adequate air circulation around the tray (a gentle fan can help) and ensure good drainage so the medium isn’t consistently soggy; and practice controlled moisture—keep the mix evenly moist but never waterlogged, watering from the bottom when possible to avoid wetting the stem base. Together, these steps create an environment less conducive to fungi that cause damping-off and help seedlings establish without collapse.