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( Pythium and Phytophthora species )

A fungal disease which attacks seedlings, the plumule rots at soil level causing the seedlings to topple over. Also attacks mature roots of cucumbers. Both genera occur naturally in the soil; they are encouraged by wet, cold soils and crowded sowings. In damp conditions they produce asexual spores which cause the infection of living tissue, these infected roots produce sexual spores that can survive for several months in dry or cold soil, which would not support the growth of the fungus.

Good hygiene and growing technique are the best means of avoiding the disease when sowing seed in trays and pots.

Use only new or sterilised containers (follow the procedure for baby's bottles) and fresh compost is essential.
Sow seeds thinly to reduce crowding and prick out as soon as the true leaves begin to appear. Wash benches, sand beds and capillary matting with hot water. Cover water tanks to keep out dead leaves which can harbour spores - it is probably better to use water straight from the tap. Avoid water-logging the growing medium (use a spray mister to water gently).

Watering regularly with chamomile tea has been shown to prevent attacks.

Cheshunt Compound (15% Copper Sulphate, 83% Ammonium Carbonate) was the traditional fungicide to use as a preventative drench when watering, diluted 5ml of powder to 570ml water. (in a handspray as a mist when growing in a propogator.) It was withdrawn from the UK market on 30th November 2010 to comply with the implementation of the provisions of Commission Directive 2009/37/EC following the inclusion of copper sulphate in Annex I to Council Directive 91/414/EEC.
Some seeds are coated with fungicide before packing.
Commercial growers use formalin foot baths at the entrance to greenhouses, which are first sterilized with steam or methyl bromide.

Back to article on Plant Diseases.