Description
This plant disease is caused by any of several species of fungi (including Pythium, Rhizoctonia, Fusarium, Phytophthora, and Sclerotium species). These fungi, common in soils throughout the world, are among the major causes of poor germination. They infect seeds and seedlings at several stages. Seeds are often attacked before they germinate. Or seeds germinate, but the growing tips are infected and killed before they emerge from the soil. Seedlings are susceptible even after they emerge. The fungi can attack the stems and roots just at or below the soil level, causing the seedlings to fall over. Although older seedlings are more resistant, damping-off fungi may still infect them, producing dark lesions on the lower stems and roots that stunt and weaken their growth. Damping-off is most severe in soil with lots of nitrogen and soil that is constantly wet. Seedlings growing in soil that is too warm or cold for rapid germination and growth are also more susceptible to infection.
Control
Incorporate sand or perlite into the soil mix to increase drainage. Don't add fertilizers that are high in nitrogen until seedlings have produced at least 1 pair of true leaves. Encourage rapid growth by planting seeds in soil that is the proper temperature for rapid germination (see Vegetable Seed Information). Also, coating seeds with a fungicide containing captan will help discourage damping-off. Cover seeds started indoors with a thin (1/6 to ΒΌ inch) layer of peat moss. (For more information on starting seeds, see Starting Seeds Indoors.)
