Cause Pythium spp. can cause damping-off and has been found on Lobelia by the OSU Plant Clinic. Pythium is favored by cool and overly moist soil conditions. It survives unfavorable periods in soil and infected plant debris. Under favorable conditions, spores germinate and infect roots. After infection, the fungus-like microorganism spreads mainly in the inner bark tissues of the root and stems. They survive as various spores in the soil, container media, or infected roots. Movement of infected plants and/or soil can spread the organism.
Symptoms Stems of seedlings or recent transplants collapse at the soil line and die. There may also be a soft, mushy rot of ungerminated seeds.
Cultural control
- Plant in pasteurized, well-drained raised beds or in soilless media. Also disinfect any tools and equipment that might be used and contaminate the media.
- Seeds should be planted when temperatures favor rapid germination and growth, so plants rapidly emerge and reach a more mature or hardened state.
- Avoid reusing pots or trays from a previous crop for propagation. If pots must be reused then wash off all debris and soak in a sanitizing solution or treat with aerated steam for 30 min.
Chemical control
- Adorn at 1 to 4 fl oz/100 gal water plus another fungicide. Group 43 fungicide. 12-hr reentry.
- Banrot 40 WP at 6 to 12 oz/100 gal water. Group 1 + 14 fungicide. 12-hr reentry.
- Subdue MAXX can be used if not phytotoxic. Group 4 fungicide. No restrictions on reentry when used as a soil drench.