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Aim to prevent fatal plant diseases due to fungi or bacteria; prevention is usually easier than cure.
Damping off This group of diseases is due to soil-bome pathogens. Sometimes, the young seedlings's stems rot at the surface of the mix and the tops fall over and die. In other cases, the seeds rot before they germinate or before the sprouts come above the mix surface - growers often (wrongly) think the poor strike is due to a bad lot of seeds. These cases are most common in cold wet conditions.
The disease often appears as a small patch of dead seedlings amongst healthy ones. If the tray is not treated promptly with a soil fungicide, the patch quickly spreads and death of all seedlings is likely.
Root rots and stem rots These diseases are due to various fungi including, for example, the notorious Phytophthora cinnamomi. The roots or lower stem become soft and brown, and seedlings may fall over. Death occurs quickly. Wet misty conditions favour the spread of these diseases.
Leaf spots Various fungi can cause brown spots of dead plant tissue on leaves. Growth slows, and deaths may occur.
Treating fungal diseases If fungal disease occurs, promptly soak the tray and contents in a suitable soil fungicide and repeat the treatment if necessary. If a tool or some other item could carry the disease from the infected tray to others, wash off all soil and disinfect the tool with a bleach mixture (20 ml of household bleach per of
water). Also, if damping off becomes a problem during cool weather, avoid watering late in the day.
If experience shows the area is disease-prone, periodically soak or spray the tray with the fungicide even before any signs of disease appear. If disease problems continue, obtain advice from a State government horticulturalist or forester, or from a local nursery.