Cause The fungi or fungus-like microorganisms, Pythium spp., Fusarium spp., and Rhizoctonia solani, attack many vegetable seedlings including members of the genus Cucurbita. Seedlings are very susceptible to infection just before and just after they emerge from soil. Seedlings that fall over or die are said to "damp-off." The disease's destructiveness depends on the amount of fungus in soil and environmental conditions, especially cool weather, wet soils, high humidity, and cloudy days.
Symptoms Young seedlings develop a sunken, necrotic lesion near the soil line. If the lesion girdles the stem, the seedling collapses and soon dies.
- In the greenhouse or seedbed use new, pasteurized soil mix. Treat any other media with heat. For example, most pathogens die if soil is heated to 158°F (70°C) for 30 min. with aerated steam.
- Ideally, use only new pots or flats. Or, thoroughly wash and disinfect old containers.
- If damping-off is observed, stop watering for a while. Allow soil around plants to dry somewhat. If seedlings are in flats or in cold frames, give them as much air and light as possible.
- Use transplants if the field has a high disease risk.
- Seed treatment.
- Captan 4F at 2 fl oz/100 lb seed plus a dye.
- Dynasty at 0.1 to 0.38 fl oz/100 lb seed plus a dye. 4-hr reentry.
- Maxim 4FS at 0.08 to 0.16 fl oz/100 lb seed plus a dye. To control pathogenic Fusarium and Rhizoctonia spp. See label for reentry restrictions.
- Mertect at 0.1 mg ai/seed plus a dye. To control pathogenic Fusarium spp.
- Orondis Gold (Group 40 + 4) at 28 to 55 fl oz/A as an in-furrow or banded soil application at planting. May be applied through drip after emergence. Preharvest interval is 5 days. 48-hr reentry.
- 42-S Thiram at 4.5 fl oz/100 lb seed plus a dye. See label for reentry restrictions.
- Quadris Flowable at 0.4 to 0.8 fl oz/1000 row feet applied in a 7-inches or less band either in furrow at planting or as a directed spray at cultivation for Rhizoctonia. 4-hr reentry.
- Ridomil Gold SL at 1 to 2 pints/A (banded or surface applied) or at 0.25 to 0.4 pint/A (directed spray to the base of the plant). See label. Not for greenhouse use or on field-grown bedding plants. 48-hr reentry.
- Actinovate AG at 3 to 12 oz/A as a soil drench at planting. 1-hr reentry. O
- Actinovate Lawn & Garden at 0.5 to 1 teaspoon/gal water. H O
- Cease at 3 to 6 quarts in 100 gal water applied to soil at 1 pint/sq ft for each 3-inches of soil depth on 21- to 28-day intervals. 4-hr reentry. O
- Double Nickel LC at 0.5 to 4.5 pints/A for soil application on 14- to 28-day intervals. Can be applied the day of harvest. 4-hr reentry. O
- Prestop as a soil drench or incorporation into growing medium. 4-hr reentry. O
- Rootshield Home and Garden at 1 to 3 Tbsp/gal water as a soil drench at planting. H O
- Rootshield WP at 3 to 5 oz/100 gal water for greenhouse soil drench and field chemigation or at 16 to 32 oz/A as an in-furrow spray. 0-hr reentry. O
- Serenade ASO (Group BM02) at 2 to 4 quarts/A. Applications can be made up to and the day of harvest. 4-hr reentry. O
- SoilGard 12G at 0.5 to 10 lb/A at 4-week intervals will suppress Pythium and Rhizoctonia. See label for specific application types and timings. Can be applied on the day of harvest. O
- Stargus at 3 to 4 quarts/A as a soil drench on 10- to 21-day intervals. Preharvest interval is 0 days. 4-hr reentry. O