Between the Vines is a biweekly column on wine and wine making in the Livermore Valley region. This column was contributed by Dr. Robert Taylor, winemaker and owner of Retzlaff Vineyards & Estate Winery.

What's happening in Livermore Valley vineyards this month?

July is the month of truth. It is in July that we see if we have mildew in the vineyard. Powdery mildew is a fungus, and it is the most common and serious vineyard pest in the Livermore Valley and throughout California. Most of our work in April, May and June has been to control this pest.

At Retzlaff, our vineyards are certified organic and we spray sulfur to control mildew. Generally, we water every two weeks and spray sulfur immediately after. We have removed leaves and extra shoots to assure that the sprays cover the entire plant and developing fruit. Now in July we learn if this effort has been successful.

Without summer watering, the vines in Livermore Valley would probably die, and for sure they would be stunted. With too much irrigation, grapes lose intense flavors.

If powdery mildew is not controlled, wine grape growth is checked, and the fruit does not develop. The result is reduced yield and smelly wine. The powdery mildew causes the grape skins to crack, so that when the grape ripens, the fruit molds and rots. This makes acetic acid, which is the main component of vinegar and has a sour taste and pungent smell. Also in July, we are cultivating and smoothing the vineyard so that it is easy to pick the grapes in August, September and October. The white grapes ripen first, followed by the reds.

Our 12 acres of vineyards were planted in 1978 and my family, the Taylors, has farmed them ever since. We grow cabernet, merlot, sauvignon blanc, semillon and chardonnay. The grapes are used to produce Retzlaff Estate-Bottled wines. Maintaining our organic faming certification from California Certified Organic Farmers takes a lot of labor and vine care vigilance. For more information, visit Retzlaff Vineyards & Estate Winery, 1356 S. Livermore Ave. in Livermore or find us online at www.retzlaffwinery.com.

wine country events

  • Dante Robere's First Wine Release -- 12 to 5 p.m. July 27 in Dante Robere Vineyards at Eagle Ridge, 10017 Tesla Road in Livermore; www.danterobere.com. Cost: free. Join Dante Robere for its first wine release. They will be pairing food with each release: 2012 Sauvignon Blanc, 2012 Estate Syrah Rose and 2010 Zinfandel. Enjoy a surprise barrel tasting.

  • Evening in the Vineyards -- 6 to 9 p.m. Aug. 2 at Las Positas Vineyards, 1828 Wetmore Road in Livermore; www.laspositasvineyards.com. Cost: Free. Join us for a free concert featuring live music by Jim Ashley and artisan pizzas by On The Vine Catering. Wine and beer will available for sale, and no outside food or beverages will be permitted. To make reservations please email info@laspositasvineyards.com or call 925-449-9463.