How to save your tomatoes or peppers from a deadly damping off disease.
Damping-off is a soil-borne fungal disease that affects seeds and new seedlings. The disease leads to the decay of germinating seeds and young seedlings. It is mainly an early season problem, causing the greatest losses in cool, wet soils.
Several different pathogens that kill or weaken seeds or seedlings before or after they germinate are the ones that cause damping off.
Although over 10 soil-borne fungi and fungus-like organisms are a cause of damping-off, only a few of them are frequently associated with the disease. Pythium aphanidermatum is one of the most important pathogens to cause damping off disease in nurseries and a major constraint in the production of tomato and bell pepper. Several fungi can cause decay of seeds and seedlings including species of rhizoctonia, fusarium and phytophthora. However, species of the soil fungus pythium are most often the trouble causer.
Damping off usually thrives when old seed is planted in cold and wet soil and is further increased by poor soil drainage. Once introduced to a seedling tray, the damping off pathogens easily move from plant to plant by growing through the potting media or in shared irrigation water.
Garden soil often contains small amounts of the damping off pathogens. If you use garden soil to fill seedling trays, you could introduce the damping off pathogens that cause the disease into the warm wet conditions best for seed growth.
There are various symptoms associated with damping off. These reflect the variety of different pathogenic organisms which can cause the condition. However, all symptoms result in the death of at least some seedlings in any given population.
Although fungi live in the soil and water, spores spread through the air and can move quickly from one seed tray, or garden row, to another. Affected plants appear as if they have been cut off at the base. Once the process is underway, it's hard to save even a few of your plants. Prevention is the best cure. The post-emergence phase is characterized by the infection of the young, juvenile tissues of the collar at the ground level. The infected tissues become soft and water soaked. The seedlings topple over or collapse.
Once tomato or bell pepper seedlings reach the 2- or 3-leaf stage, they are no longer susceptible to infection by Pythium or Rhizoctonia; however, Phytophthora can infect tomato or pepper plants at any stage. Older plants hardly succumb to damping off because the production of secondary stem tissue forms a protective barrier and limits fungal penetration.
There is no cure for plants that already have damping off. However, you can easily prevent the problem by providing good air circulation.
Here are some of the ways of preventing damping off.
Seed treatment with fungal culture Trichoderma viride (4 grams per kg of seed) or Thiram (3 grams per kg of seed) is the major preventive measure to control the pre-emergence damping off. You can also Spray 0.2% Metalaxyl when there is cloudy weather.
Sowing seeds in a sterilized growing medium can be effective, although fungal spores may still be introduced to the medium, either on the seeds themselves or after sowing (in water or on the wind).
To reduce survival of the pathogens, remove and discard diseased plants, and sterilize containers to remove dust, planting medium, and soil particles in which spores can survive.
If possible, avoid planting when the soil is cool; seeds germinate faster and seedlings are more vigorous when the soil is warm, so they are less likely to be damaged. The use of fungicide seed treatments can help prevent damping-off. When seedling loss is extensive, replanting may be necessary.
Never water your seed bed or young tomato or pepper plants after mid day, so that the soil surface and the plants are dry by evening. Also avoid over-watering young tomato and pepper seedlings.
Sterilize all used pots and trays in a solution of 10% household bleach by soaking for 30 minutes. Use new potting mix to fill trays. Don't reuse potting mix and don't use garden soil or compost.
Select well-draining nursery sites away from tomato or pepper fields.
Elevate seed beds to improve drainage and avoid placing nursery in a humid place. Do not over water because this favours the diseases. You may only irrigate early in the day to allow rapid drying of leaves.
Disinfect seedling pots and trays with bleach (=NaOCl) before storage. Wear gloves or wash hands with water afterwards, because bleach is toxic.
Uproot diseased seedlings. Bury deeply, or put into plastic bags and burn. Once your seeds or seedlings are affected, chemical sprays are of no help. However, Further spread can be slowed by spraying products containing mancozeb.
Do not apply fertilizer to seedlings until several true leaves have developed. Then apply 1 quarter strength standard soluble fertilizer. Many potting mixes contain slow release fertilizer and do not require any fertilizer application.
Maintain a low pH. Your tomato or pepper plant's possibility of suffering from damping off gets higher as the potting mix or garden soil pH rises. Municipal water usually contains chlorine and therefore it's normally alkaline. So if you water your garden or seedbed with tap water, you are therefore constantly increasing the pH of your soil. Therefore, your tomato or pepper plants' probability of suffering from damping-off disease increases. So always know the pH of your tap water as well as the pH of your soil and make sure you always strive to maintain a pH of around 5.5.