Sulfur is usually applied at night, when winds are calm

This time of year -- usually at night -- you see tractors going through vineyards in the Gap, putting out clouds of dust or a fog of droplets. What is the stuff they're putting on the vines, is it harmful, and why are they doing it under cover of darkness?

It's the battle that goes on in every vineyard: man vs. mildew. Powdery mildew affects grapevines around the world, just one of many threats -- critters, insects, diseases, weather phenomenon --that can ruin a promising crop. So what are they putting on those vines? Are they polluting the environment and contaminating the wine you drink?

The answer is NO! Early sprays are usually sulfur or copper dissolved in water, or mineral oil in solution. Some growers use a dry application of micronized sulfur powder. All of these materials are certified organic and are also typically used on the produce you buy at the farmers' market or supermarket. Sprays later in the season may include stronger fungicides, but the trend today is to use the most environmentally friendly materials possible; often these are biological fungicides. If a vineyard is certified as "Sustainable," "Organic," or "Biodynamic" you can be sure the grower is committed to using only very "soft" products -- often a wine label will give you that information.