Red Thread Disease

redthread.jpg (115420 bytes) Red thread disease on turfgrass.

This fungal disease is common on all amenity grasses although it is perhaps more common on ryegrasses and fescues.

It is caused by the fungus Laetisaria fuciformis (formerly Corticium fuciforme).

The fungus is favoured by periods of mild, damp weather which means that it can now be seen causing damage to turfgrasses throughout the year.  Red thread is a disease commonly associated with turf that is growing under low fertility conditions.  However, I am seeing an increasing number of affected turfgrass areas which have been maintained under adequate nutrition.

Initial symptoms of this disease are small watersoaked* patches on the leaf tissues.  These may well go unnoticed as the disease progresses rapidly to show areas of dry, straw-coloured turf which vary in size from 5-35cm in diameter.  Amongst the straw-coloured plants will generally be seen numerous red sclerotia* which give this disease its common name.  The margin between the affected and adjacent unaffected plants is quite diffuse but patches can coalesce to form large areas of affected turf.

Although the fungus is capable of infecting the crown of the plant, the disease is almost invariably contained within the leaf tissues.  As such, this disease, however damaging it may appear, almost never causes death of the plant and scaring of the sward is extremely rare.

*Watersoaked This is a term generally used to describe the appearance of leaf tissue that has become wet-looking, generally darkened and translucent as a result of fungal infection breaking down the internal structure of the leaf.

*Sclerotia These are masses of fungal hyphae which are bound together in hard structures which allow the fungus to survive periods of adverse environmental conditions.