Black mold

A picture of a grape leaf plant suffering from black mold

English name: Black Root

The scientific name:Guinardia Bedwelli bidwellii Guignardia

The type of disease: A fungal disease

family: Gnomoniaceae


Black mold affects the leaves, buds and fruit sets of grape vines. On the leaves, they appear as small reddish-brown circular spots that enlarge and develop tan or white centers with dark borders. These spots may coalesce, causing the leaf to become distorted or fall off. On fruit, the disease causes brown circular lesions that turn black as they ripen, causing the mummified berries to wilt.

Close-up of the automatically generated description sheet
Black grape rot.
Controlling grape diseases, spring 2021 | Cornell Fruit Resources: Grapes


Black mold is caused by the fungus Guignardia bidwellii, which can live on residue

Infected plant and canes.

Propagation conditions

Black mold prefers warm, humid conditions with frequent rainfall or overhead irrigation. The fungus produces spores (ascospores and conidia) that can be spread by wind, rain or water splashes.

Disease course

The black rot fungus overwinters as immature fruiting bodies (pseudothecia) on infected sticks, leaves, or mummified berries. In the spring, when temperatures are favorable and humidity is present, the pseudocospores mature and release ascospores that initiate the primary infection. The fungus then produces conidia on this primary infection , which can cause secondary infections throughout the growing season.


Severe black mold infection can lead to significant leaf drop, fruit rot, and reduced yields. Disease can also weaken vines, making them more vulnerable to other pathogens and environmental stresses.

Control strategy

An integrated approach that includes cultural practices, pruning, and fungicide applications is recommended for black mold management.

Preventive measures

Remove and destroy infected plant remains, prune and dispose of diseased canes, and ensure good air circulation in the vineyard.

Organic/chemical control

For organic control, copper-based fungicides (such as copper hydroxide and copper sulphate) can be effective when applied preventatively. Chemical fungicides containing active ingredients such as mancozeb, captan or ziram can also be used according to label instructions.


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