Red Thread
Risk near you, next 48h
See whether your local forecast favours this disease right now.
When it strikes
Watch it before you act
At this level the damage rarely costs the crop. Note the date, check twice a week, and act only if it reaches new growth or the weather turns favourable for it.
Rain and irrigation splash
Water splashing off soil and infected leaves carries it upward and along the row. Watering at the base and mulching the soil surface break the route.
It carries over to next season in soil, debris or seed — which is why rotation matters here, not just treatment.
Hot compost only
A heap that reaches and holds 55–65°C throughout will destroy it. A cool corner heap will not, and will return the problem to the beds with the finished compost.
When and where to look
Scout the planting while temperatures hold between 15°C and 25°C, with humidity above 85%, after rain or heavy dew, while the leaves are still wet. Risk builds after roughly 10 unbroken hours of those conditions, so the morning after such a night is the moment to look.
Rule these out first
Same category, and at least one host crop in common — so they are genuinely confusable in the same part of the garden.
The signs that lead here
Full problem lists for these crops
About
Red thread (Laetisaria fuciformis) is the classic disease of an underfed lawn in a mild, damp summer. It is disfiguring rather than destructive: it attacks the leaf blade but not the crown or roots, so a lawn almost always recovers once its nutrition is corrected.
Symptoms
Irregular bleached or pinkish patches from 5 to 30 cm across. Close up, tiny coral-red needles or threads bind the grass blades together at the tips — the feature that gives the disease its name.
Organic Treatment
Feed the lawn: a nitrogen-containing feed usually grows the problem out within three weeks. Collect the clippings while symptoms are visible, and improve surface drainage and airflow by scarifying out the thatch layer.
Chemical Treatment
Rarely worth spraying in a garden. If a fine ornamental lawn justifies it, a systemic turf fungicide will clear it, but correcting nitrogen is both cheaper and longer-lasting.
Prevention
Feed regularly through the growing season rather than in one spring dose, mow with sharp blades at the right height, scarify annually, and aerate compacted ground so the surface dries after dew.
Crops at risk
Related problems
Red Thread risk by location
Each location has a month-by-month profile computed from the weather archive: how many hours a year actually meet this disease’s thresholds.