Planting a new vineyard in a weedy field is a bad idea. Weeds would compete with the small vines for moisture, space, nutrients and light which would set back their growth. Thus, in establishing a new vineyard, growers need to clear the weeds out. Most growers use synthetic chemical herbicides when planting a new vineyard due to the high cost of hand weeding and negative effects of tillage. Using herbicides is an option for organic growers since the small vines do not produce grapes for several years which corresponds to the waiting time to be certified as organic.
“…weed management is the most expensive and technically challenging practice for organic grape production, and many organic farmers rely on mechanical and hand cultivation for weed control. Although these methods are highly effective, they are also labor intensive, more expensive, and their sustainability is questionable from a labor and environmental perspective.
Another option would be to use conventional production techniques that use synthetic herbicides during the establishment phase, and once established, transition the vineyard to achieve organic certification.”
Authors: Olmstead, M., et al.
Affiliations: Department of Horticultural Sciences, University of Florida.
Title: Weed control in a newly established organic vineyard.
Source: Hort Technology. December 2012. 22(6):757-765.
Powdery Mildew On Grapes
Powdery mildew exists wherever grapes are grown for wine. The fungus that causes grape powdery mildew is an obligate parasite, which means it must grow on grape tissue and will not parasitize any other species of plants. The fungus penetrates only the epidermal cells sending tubular suckers into them to absorb nutrients. The mass of fungal growth on grape skin give the impression that the grapes are sprinkled with flour. This impression is enhanced by the smell of moldy flour released by the diseased grapes. Fungicide sprays effectively control the incidence of powdery mildew of grapes from 99% to < 1% which is very important for the quality of wine.
“Analysis of wines made from powdery mildew-affected grapes has revealed that even slight infection leads to compositional changes, an oily mouthfeel and undesirable fungal/earthy flavours when compared with wines made from disease-free grapes.
The strongest link to the effect of powdery mildew was elevated ratings of ‘oily’ and ‘viscosity’ attributes in wines made from grapes with as little as 1-5% powdery mildew compared to wines made from disease free grapes.
…wines made from diseased grapes were rated as having more pronounced fungal, earthy and cooked tomato aroma attributes than wines made from uninfected grapes.
Juice from the most severely diseased grapes had a dusty and mushroom aroma and acid taste compared to the others.
When subjected to the heat test, wines made from grapes with severe powdery mildew showed greatest haziness, so there is the potential for spoilage of wine during storage due to haze.”
Authors: CRCV Update
Title: Powdery mildew impacting on wine quality
Source: Wine Industry Journal. 2004. 19:71-75.