With Spring approaching and rains coming and going during our last few weeks here in San Luis Obispo, we thought it would be good to discuss what we are going to be doing in the vineyards as the buds are beginning to break.
The key to maintaining a sustainable practice for mildew is PREVENTION.
A reasonable question would be why not wait until it is found in the vineyard? Mildew is unique, in that once it is established in the vineyard, the eradication and control of its spread can result in ten times the labor, fuel and material inputs. Mildew can easily ruin wine quality and render individual clusters worthless and in this growing region, it will grow every year.
Tolosa will begin its prevention program at the start of shoot growth by completely washing the vine with a light mixture of a highly refined, pure mineral oil and water. When applied properly, this important and sustainable practice eradicates over wintering mildew spores and starts the new vine growth free of infection. From that moment on we begin to monitor our field weather stations to time the durations of humidity and temperatures conducive to mildew reproduction. This data is then used to model the timing of the next sprays.
Later this spring Tolosa will remove unnecessary leaves and shoots around each grape cluster to minimize congestion. By taking this important step, the resulting spray coverage will be complete as possible for total prevention, and therefore control of mildew. An additional benefit of this work is that, if rain this year falls before harvest, these clusters will dry more quickly and as a result be naturally more resistant to mold and degradation.
Spring's first spray, monitoring field weather stations, shoot spacing, shoot thinning, shoot positioning into uniform upward growing tips, and ultimately the removal of leaves surrounding the developing grape cluster are all considered important practices in Tolosa's sustainable program to minimize wasted fuel, labor and material use .
Jim Efird, Tolosa Partner & Viticulturist