Wednesday, October 24, 2012

Powdery Mildew - UPDATE 24/10/2012

Powdery mildew is the main fungal disease that most grape growers confront every seasons.  Many grape growers struggled to keep powdery mildew under control in vineyards, as once your vines are infected and the symptoms are visible, the disease already is in an advance stage of development. 

DJ's have specialist skills, based on experience, in detecting the disease early in the season. This week we have detected the following symptoms.

1. A powdery mildew a flagshoot - A small amount of powdery mildew 
 at this point in the season becomes a significant amount at harvest. 
McLaren Flat 22/10/2012.
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.

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