As part of CropWatch McLaren Vale and commercial monitoring I study the spread of powdery mildew (and in certain years when we have outbreaks downy mildew) from abandoned vineyards. I use these vineyards to get photos of disease and make observation of spread etc.
My considered opinion is disease does spread from abandoned vineyards to neighboring properties and that this increases the cost of disease control in adjoining vineyards.
For the big three fungal disease, powdery mildew, downy mildew and botrytis, the pressure was very high last season (Vintage 2011). High pressure last season has both positive and negative consequences for this season. If you had good control last season, then you know that your spray programme was robust, and you have a low level of disease carrying over to this season.
Unfortunately if you had a significant amount of disease last season you are likely to begin this season with a higher pressure than in a clean vineyard.
Powdery mildew is influenced by the amount of inoculum inherited from last season. Downy mildew survives in the soil for a great length of time, so it will be present for many years after widespread infections in the 2010/11 season.
The first ten weeks of the season will be critical to keeping your fruit clean from both powdery & downy mildew. Powdery mildew early season control is critical to win the battle control next season’s disease this season. Downy mildew protection will also be important if we have a wet grapevine growing season.
Unfortunately there is one factor that you have no control over. How clean are neighboring vineyards? Contrary to what is often reported we can identify many situations where unprotected vineyards are having a significant build up of disease, which in turn is spreading into surrounding tended vineyards.
|Downy mildew on abandoned Grenache, Whites Valley 5172 - Dec 2010.|
Abandoned vineyards are one of the main issue the industry faces, other than an over supply of fruit, the increased disease pressure from abandoned, or poorly tended vineyards.
Abandoned vineyards are a potential host of pests and diseases and can be a significant concern for neighboring properties. Unfortunately it would seem that there is not relevant legislation that makes a basic level of care a legal requirement in South Australia. In our opinion farm owners have a moral obligation to manage the risk of an abandoned vineyard.
During Vintage 2011 several abandoned vineyards in the McLaren Vale region greatly increased the levels of powdery mildew and downy mildew in adjoining vineyards.
|Approximate spread of powdery mildew by January 2011*. The 150 meter radius of disease affects five separate vineyards and significantly increases the disease pressure in these vineyards.|
*This vineyard was featured in our earlier post - Vineyard Photos - What is looks like inside an abandoned vineyard.
It is now time to put pressure on farm owners who did not tend their vineyards last season. They need to be tended or pulled out for the sake of their neighbors and the sake of the wider grape industry.