Dampingoff diseases

These are usually caused by a group of closely related fungi, although certain other organisms can cause damping-off. These fungi cause problems to germinating seedlings when threads of the fungus, which resemble fine cotton-wool, spread rapidly in the soil or over the compost surface. As it comes into contact with seedlings the parasitic fungus penetrates the tissues, which then die. The problem is particularly acute as these fungi are always present in soil or compost and are capable of survival without parasitism. Old soil or compost, therefore, provides a source of infection and should never be re-used for seed sowing or cuttings. The effects are compounded when seedling densities are high; if temperature conditions are too hot or too cold for strong seedling development; if ventilation is poor and the soil too damp; and if the seedlings or cuttings suffer frost damage.

The disease can be recognized when seedlings or cuttings suddenly die in patches.

To avoid damping-off disease sow seeds at a correct density so that the seedlings are not overcrowded; give them plenty of light, air and warmth, and do not overwater. Spray the seedling area before germination with a solution of Captan or a copper fungicide. Further control may also be achieved after the seeds have emerged by spraying again with Captan or zineb.

If damping-off diseases do become established, the seedlings or cuttings should be sprayed with Captan, which will limit the disease, or with a copper fungicide, which will usually kill it off. Unfortunately copper is toxic to some plants, so check the instructions carefully before applying a fungicide containing copper.

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