🍄Fungal diseasesSevere
Grape Black Rot
Risk near you, next 48h
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When it strikes
Temperature
15–27°C
Humidity
≥85%
Leaf wetness
Required
Season
Spring, Summer
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.