Cause The fungi or fungus-like microorganisms inlcuding Pythium spp., Fusarium spp., and Rhizoctonia solani can attack young seedlings of many vegetables crops. Seedlings are susceptible to disease before or after emerging from soil. If seedlings are affected before emerging, it presents as poor germination. If disease develops after plant emergence, seedlings may fall over or die and are said to have "damping-off." The disease's destructiveness depends on environmental conditions and the level of pathogens in the planting medium. Cold, wet planting medium, high humidity, overcast conditions, and overcrowding are especially favorable to damping-off. Poor ventilation in greenhouses and contaminated planting medium or equipment also favor 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, seedlings simply may not emerge.
Cultural control
- In the greenhouse, pasteurize the planting medium with heat. For example, most pathogens die if soil is heated to 158°F (70°C) for 30 min. with aerated steam. Do not reuse any planting medium that has had damping-off problems unless it is treated with heat, aerated steam, or chemical disinfectants.
- If damping-off occurs, stop watering for a while and allow the planting medium to dry somewhat around the plants. If the seedlings are in flats or in cold frames, give them as much air and light as possible.
- Use good sanitation in greenhouses; clean pots and trays between batches of transplants. Wash pots and trays well to remove adhering planting medium and plant debris. Follow up with a chemical rinse or soak, such as a 10% bleach solution or 3% hydrogen peroxide. Benches should be cleaned between transplant production cycles. Avoid placing trays of plants on the ground where they can contact raw soil.
Chemical control
- Treat seed with registered fungicides. See specific fungicide labels to determine which greenhouse vegetable transplants are included on the label.
- Apron XL is labeled for control of Pythium spp. in many vegetable crops, including globe artichoke, leafy vegetables including brassicas, sweet corn, cucurbits, solanaceous vegetables, root and tuber vegetables, legumes, and alliums.
- Dynasty is a broad-spectrum fungicide and is labeled for control of Fusarium and Rhizoctonia spp. in many vegetable crops, including certain leafy vegetables, head and stem brassicas, sweet corn, cucurbits, solanaceous vegetables, root and tuber vegetables, legumes, and alliums.
- Maxim 4FS is labeled for control of Fusarium and Rhizoctonia spp. in many vegetable crops, including certain leafy vegetables, head and stem brassicas, herbs, sweet corn, cucurbits, solanaceous vegetables, root and tuber vegetables, legumes, and alliums.
- 42-S Thiram is a broad-spectrum fungicide and will help to control of Fusarium and Rhizoctonia spp. It is labeled for many vegetable crops, including leafy vegetables, brassicas, sweet corn, cucurbits, solanaceous vegetables, root and tuber vegetables, legumes, and alliums.
- C-O-C-S WDG at 4 lb/100 gal water or at 2 oz/3 gal water. Can be re-applied on a minimum of 3-day intervals. Do not apply through any irrigation system. 24-hr reentry for greenhouse applications.
Biological control Many biocontrol formulations are registered for use on a wide array of vegetable and herb crops. See specific product labels to determine which greenhouse vegetable transplants are included.
- Actinovate AG at 3 to 12 oz/A as a soil drench at planting. 4-hr reentry. O
- Actinovate Lawn & Garden at 1/2 to 1 teaspoon/gal water. H O
- Bexfond as a soil drench at planting. O
- Cease at 3 to 6 quarts in 100 gal water 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. 4-hr reentry. O
- Mycostop at 0.07 oz/lb seed. 4-hr reentry. O
- Prestop WG as a soil drench or incorporation into growing medium. 4-hr reentry. O
- Rootshield WP as a seed treatment or at 3 to 5 oz/100 gal water for greenhouse soil drench. 4-hr reentry. O
- SoilGard at 2 to 4 oz/100 gal water as a greenhouse drench Pythium and Rhizoctonia. See label for specific application types and timings. 4-hr reentry. O
- Stargus at 3 to 4 quarts/100 gal water as a soil drench on 10- to 21-day intervals. 4-hr reentry. O
- Taegro 2 at 2.6 to 5.2 oz/A on 7- to 14-day intervals. 4-hr reentry. O
- Tenet WP at 2.5 to 7.5 oz/100 gal water as a soil drench will suppress certain fungal pathogens including Fusarium, Rhizoctonia, and Pythium spp. See label for specific application types and timings. 4-hr reentry. O