Cause Damping-off can be caused by Pythium spp., Fusarium spp., Rhizoctonia solani, Alternaria spp., and other fungi. These soilborne pathogens attack young seedlings of many vegetables in the Willamette Valley, including members of the genus Brassica, as well as cause root rot of more mature plants. These soilborne fungi can persist indefinitely in soil or plant debris. If seedlings are affected before emergence, it appears as poor germination. If the decay is after emergence, seedlings that fall over or die are said to "damp-off." The destructiveness of this disease depends on the level of pathogens in the soil and on environmental conditions. Wet, cool soils are especially favorable for the development of seed rot and damping-off.
Symptoms Young seedlings develop a sunken, necrotic lesion near the soil line. If the lesion girdles the stem, the seedling collapses and soon dies. Also, seeds may simply not emerge.
Cultural control
- Do not sow seeds deeply and sow into warm soils.
- Apply fertilizers properly, inadequate or excessive applications favors damping-off.
- Remove or encourage decomposition of plant debris.
Chemical control Treat seeds with one of the following fungicides.
- Acquire at 0.25 to 0.5 fl oz/100 lb seed plus a dye for Pythium spp. only. Cannot be used for edible oil or any other human/feed consumption. 24-hr reentry.
- Allegiance-FL at 0.25 to 0.50 fl oz/100 lb seed plus a dye. Controls Pythium spp. only. See label for reentry restrictions.
- Dynasty at 0.1 to 3.75 fl oz/100 lb seed plus a dye. 4-hr reentry.
- Helix XTra (Group 3 + 4 + 12) at 23 fl oz/100 lb.
- 42-S Thiram at 6.4 fl oz/100 lb seed plus a dye. See label for reentry restrictions.
Biological control Efficacy unknown in Oregon.
- Double Nickel LC at 0.5 to 4.5 pints/A on 3- to 10-day intervals. Can be applied the day of harvest. 4-hr reentry. O
- Stargus at 6 to 8 fl oz per 1,000 ft row as an in-furrow treatment. Preharvest interval is 0 days. 4-hr reentry. O