Plant Diagnosis

Damping-off of Seedlings Critical

A fungal disease causing seedling death shortly after germination caused by Pythium, Rhizoctonia, Fusarium etc during December–March.

Description

Fungi causing damping-off are soilborne and can be found anywhere even small amounts of soil and dirt are left including reused seed trays and benches. Once the seed is planted and watered, fungal spores or mycelium will start to colonize the soil in the trays. The chance of having an outbreak of damping off is increased when seedlings are kept very wet. Pythium, for example, is a fungal-like organism that has motile spores. The spores have hair-like appendages (flagella) they use to propel themselves in a film of water from tray cell to tray cell. Damping-off pathogens present on dirty greenhouse benches can colonize the soil in seed trays through openings in the tray bottom. Once one seedling shows symptoms in a seed tray, neighboring seedlings are often infected as well.

Symptoms

• Seedlings fail to emerge or collapse soon after germination. Water-soaked lesions at the base of the stem. The lower stem turns brown or black and the seedling falls over.