Non-botrytis bunch rots
Bunch rots on grapevines can be caused by a range of fungi, yeasts and some bacteria, including acetic acid bacteria. This page discusses rots that are not caused by Botrytis cinerea.
Cladosporium rot
Non-botrytis bunch rots don’t look the same as B. cinerea (grey mould). Many of the non-botrytis bunch rots produce black moulds and look similar, while others are more distinctive. Some of the more frequently encountered non-botrytis bunch rots found in vineyards are:
- Alternaria rot
- Aspergillus rot or black sooty mould
- Bitter rot or Greeneria rot
- Black spot or Anthracnose of grapes
- Botryosphaeria rot
- Cladosporium rot
- Penicillium rot or blue mould
- Rhizopus rot
- Phomopsis rot
- Ripe rot or Colletotrichum rot
- Sour rot
The majority of fruit-rotting diseases are caused by fungi. Many are opportunistic pathogens that infect berries through wounds (e.g. berry splitting after rain events).
Fungi produce many spores, which can be dispersed by wind, dust and rain. Insects can carry them on feet or mouthparts. The diseases can carry over from the previous season on mummified berries, dead wood, bark, canes and spurs, vineyard debris and decaying vegetation, or in the soil. Many of the fungi associated with non-botrytis bunch rots can also be found on the vegetative parts of the vine, such as the leaves, shoots and wood (e.g. in Botryosphaeria rot).
Like botrytis, other berry rots are favoured by wet weather and high relative humidity during the growing season. Higher rainfall increases the risk and amount of these diseases. A sequence of favourable seasons can increase the incidence and severity of these diseases. Some grapevine varieties are more likely to be affected than others, particularly if they have dense clusters and vigorous canopies.
There are several viticultural practices that vineyard managers can employ to reduce the risk of non-botrytis bunch rots. These include variety selection, canopy management, avoiding pockets of excessive moisture in the vineyard, vineyard hygiene and the use of fungicides.
Bunch rots reduce grape yields and have negative effects on grape and wine quality.
Video
Non-botrytis bunch rot
Practical management options for controlling non-botrytis bunch rot.