Snow Mould (Fusarium Patch)
Risk near you, next 48h
See whether your local forecast favours this disease right now.
When it strikes
Treat, then re-check in 5–7 days
Pick off the worst material, apply the organic option below, and look again after five to seven days. If the spread continued, escalate rather than repeating the same treatment.
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 -2°C and 8°C, with humidity above 90%, after rain or heavy dew, while the leaves are still wet. Risk builds after roughly 24 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
Snow mould (Microdochium nivale) is the commonest lawn disease of the cold half of the year. It works at temperatures close to freezing under prolonged wet or snow cover, which is why the damage often only appears as the snow melts in late winter.
Symptoms
Round patches 5–30 cm across of yellowed, then greyish-brown, matted grass. In damp mornings the edge of a patch carries white or pale pink cobwebby mycelium. Patches merge into large dead areas in a bad winter.
Organic Treatment
Rake affected areas gently to break up the mat and let the surface dry. Brush off heavy dew on winter mornings, keep leaves swept off the lawn, and overseed the scars in spring once soil temperatures recover.
Chemical Treatment
Iprodione or a fludioxonil-based turf fungicide applied preventively in late autumn is effective, but for a garden lawn the cultural measures below are usually sufficient and far cheaper.
Prevention
Stop feeding nitrogen after early autumn — soft late growth is what the fungus attacks. Scarify to reduce thatch, aerate compacted areas, avoid walking on frosted grass, and never leave the last cut too long going into winter.
Crops at risk
Related problems
Snow Mould (Fusarium Patch) 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.