Grape Black Rot
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.
Keep out of the compost
This survives a garden heap. Bag it for municipal green waste, which is composted industrially at temperatures a garden heap cannot reach, or burn it where that is permitted.
When and where to look
Scout the planting while temperatures hold between 15°C and 27°C, with humidity above 85%, after rain or heavy dew, while the leaves are still wet. Risk builds after roughly 7 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
Black rot (Guignardia bidwellii) is the most serious fungal disease of grapes in warm humid regions, destroying entire clusters in wet seasons if left unmanaged.
Symptoms
Tan circular leaf spots with dark borders dotted with black specks; berries turn brown then shrivel into hard black mummies that stay on the cluster.
Organic Treatment
Remove mummified berries and infected canes, open the canopy, and apply sulfur or copper from early shoot growth through fruit set.
Chemical Treatment
Mancozeb or myclobutanil from 2.5 cm shoots through 4–5 weeks after bloom, the critical infection window.
Prevention
Sanitise by removing all mummies, train vines for airflow, prune annually, and site vines in sun with good drainage.
Crops at risk
Related problems
Grape Black Rot 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.