DISEASE

NAME
Damping-off
Various Damping-off Species


Description
A soil based fungal problem that involves three types. Pythiumspecies, Phytophthoraspecies and Rhizoctoniaspecies, which is the main cause of wire-stem and produce brown fungal threads if a part of the leaf touches the soil.
The Pythiumultimumis also responsible for root rot of succulent or tropical plants.

Symptoms
The fungal attack can occur below (pre-emergence) before the seedling appears or above soil level (post-emergence) as the seedling develops cotyledons. The rot occurs on the roots and can move into the stem making the seedling to topple or the fungus attacks the outer layer of the stem only leaving a thin cord to support the plant (wire-stem). It may also produce fine threads that spread from the top of the seedling to other seedlings. In succulent nursery stock the fungus rots the roots causing the death of the plant.



Source and Dispersal
These funguses are found in soil and Pythiumspecies can be transmitted in water, as in irrigation. Insects, animals and contaminates soils or containers are also responsible for dispersal.

Favoured Conditions
It prefers wet soils and a warm humid environment as in a propagation glasshouse.

Affected Plants
It affects all seeds and seedlings and Aloeor Haworthia species, nursery stock.

Aloespecies especially in a nursery situation are venerable to the Root Rot (Pythiumultimum).

Begoniaand Delphiniumspecies are infected by (Pythium debaryanum) and (Pellicularia filamentosa). These fungi attack seedlings or cuttings causing death.

Rhododendronand Callistephusspecies are infected by the fungus (Pellicularia filamentosa) particularly when over watered causing stem rot in older plants and infects seedlings.

Robiniaspecies seedlings are infected with (Phytophthora parasitica) normally in a nursery situation.

Brown Patch Agrostis palustris     

Turf Grasssuch as Agrostis palustris(Bent), Festuca arundinacea(Fescue) and Cynodonspecies (Couch) are infected by Brown Patch(Rhizoctonia solani). This fungus forms brown discoloured areas that turn white-grey up to 50cm across with a brown smoky coloured border. It is found in particularly heavy thatched turf in warm humid conditions. Excessive nitrogen and poorly drained soils favour infection and can be seen in the early morning when the dew is on the turf. It is active from spring to summer and may be associated with other fungal attacks.

Turf Grassis also infected by Damping Off (Pythiumspecies) affecting many cool seasonspecies and several warm season species. Yellow patches appear, with the seedlings of new lawns becoming stunted and the seedlings are covered in water soaked lesions, which kills them. Mature lawns can also be infected.
Pythiumspecies also cause Rootand Crown Rotin cool or warm season turf that is in wet soils or have excessive thatching. Improved drainage and minimal thatch will reduce infection.

Non-chemical Control
Avoid overhead watering of seedlings, and allow the soil to drain before rewatering. Avoid wet boggy soils and sow the seedlings thinly avoiding over crowding. Improve air circulation and infested seedlings with there soil should be discarded.
Heat treat the growing media before use and disinfect containers.

Chemical Control
There is a range of systemic fungicides suitable for controlling this problem. Furalaxyl will control Pythiumand Phytophthoraspecies and Quintozene may be used to control Rhizoctoniaspecies.
Note
Always read the label for registration details and direction of use prior to application of any chemicals.