|2 & 3. Powdery mildew on the reverse side of the leaf. Willunga 23/10/2012.|
|Leaf spots in an abandoned vineyard. Willunga 23/10/2012.|
|4. A powdery mildew flagshoot in Grenache.|
Note the upturned lower leaves covered in white fungal growth.
Infections at this time of the season are very serious. One of the vineyards pictured above in Willunga has 4-6 powdery mildew infections per panel (2 & 3), this will obviously turn into a ranging infection of the next four weeks if the vineyard remains unsprayed.
Berries are extremely susceptible from the immediate capfall stage (EL-18) through fruit set (EL-30). This is the most critical time to keep powdery mildew under control. Severe powdery mildew infections on the clusters is usually a result of poor fungus control and canopy management throughout this period.
Maintaining proper airflow and sunlight penetration into the vine will ensure a “drier” micro climate inside the vine. Direct contact with sunlight will also kill powdery mildew spores and reduce the chances of crop loss. This can be achieved with good canopy management.