Red Thread Disease - Laetisaria fuciformis
A disease of lawns in the late summer and autumn months, especially in lawns of low fertility, especially Nitrogen. If the summer months are humid and moist there will be an incredible outbreak of this disease on UK lawns.
This disease is now thought to be a combination or complex of two fungal species:
a) L.fuciformis – Red Thread – where the red needles are present
b) L.fuciformis – Pink Patch – where the pink mycelium is present
Where has it come from?
Red Thread naturally occurs as a Pathogen within the turf grass seed and ultimately the mature grasses. The grass seed breeders work hard to cultivate species and varieties of grasses that have ‘freedom of Red Thread’ pathogens. Buying certified and quality grass seed with known Species and Cultivars in the mixture is a good start! It can occur mostly in turf and lawn areas of low fertility levels, particularly Nitrogen. As grass growth slows down due to a lack of Nitrogen, the disease becomes more prevalent. If an area of lawn has recently been fertilised and some of the lawn was incorrectly missed and remains unfertilised, you will get more disease in the part that was not fertilised properly. Remedy this small strip or area by fertilising the missed areas.
Will it kill the lawn if left untreated?
Red Thread does not actually kill the grasses, merely making them look a bit straw like and unsightly, especially once the disease has caused the damage and dried up. Grass plants are rarely totally killed.
Grass species involved
Red Thread Disease can affect most turf grass species, but particularly Red Fescue (Festuca rubra) and Perennial rye grass (Lolium perenne) although the majority of cool season grasses as found in the United Kingdom can suffer an outbreak
What are my options on control of the disease?
Improve fertility levels immediately, especially Nitrogen and Potassium. Feeding a lawn little and infrequently is the worst culprit! Adopt a regular planned feeding programme. Summer control can almost always be assisted by the application of Nitrogen. Winter attacks also pose a problem on fine lawns and an adequate nutrient level must be maintained if the lawn has a history of attack.Choose disease resistant cultivars for initial sowings, repair and over sowing. Maintain a soil pH of 6.5-7.0. Ensure the lawn is mown with a mower with a sharp blade so that the grass leaf is not damaged and weakened. There is little benefit to be gained from an application of a turf fungicide.
Sometimes, even if you are fertilising your lawn on a regular basis, your lawn may still get an attack of Red Thread Disease but not as bad as an unfertilised lawn. The lawn will be telling you that nutrient levels are getting low in the soil's nutrient bank account! React to what the lawn is telling you!
A downloadable .PDF version Red Thread Disease is available here