Pythium Damping Off
Pythium spp. (P. ultimum, P. irregulare, P. aphanidermatum)
Overview
A common oomycete disease that attacks seeds and seedlings, causing pre- and post-emergence damping off. Seedlings collapse at the soil line as the stem becomes water-soaked and constricted.
Symptoms
Seeds fail to germinate (pre-emergence damping off). Seedlings collapse at soil line with water-soaked, constricted stems (post-emergence). Roots are brown, mushy, and sparse. Patches of dead seedlings in seed beds.
Environmental Conditions
Humid
Prevention
Use sterile potting mix. Avoid overwatering. Ensure good drainage and air circulation. Sow seeds at proper depth. Avoid overcrowding. Use treated seed when available.
Management
Improve drainage and reduce watering. Apply biological controls (Trichoderma, Bacillus). Drench with phosphorous acid products. Remove dead seedlings. Allow soil surface to dry between waterings.