Apple Scab
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.
Wind-blown spores
Spores travel on air well beyond the affected bed, so a neighbouring garden can be the source. Spacing and airflow matter more than distance from your own infected plant.
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 6°C and 26°C, with humidity above 80%, after rain or heavy dew, while the leaves are still wet. Risk builds after roughly 9 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
Apple scab (Venturia inaequalis) is the most important disease of apples and crabapples in temperate climates, infecting leaves and fruit during wet spring weather and disfiguring the crop.
Symptoms
Olive-green to brown velvety blotches on leaves that later turn black; corky, cracked scabby lesions on fruit; early leaf drop in severe cases.
Organic Treatment
Rake and destroy fallen leaves to break the cycle, apply sulfur or copper from bud break through wet spring weather, and prune for airflow.
Chemical Treatment
Myclobutanil, captan, or dodine applied on a protectant schedule during the primary infection period (green tip to petal fall).
Prevention
Plant scab-resistant cultivars, remove leaf litter in autumn, prune open canopies, and avoid wetting foliage.
Crops at risk
Related problems
Apple Scab 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.