Bud break is at hand, and frost is an ever-present threat, which is why grape growers should follow appropriate cultural practices to mitigate the risk.
“A vineyard should be free of tall cover crops and weeds and have well-irrigated, firmly-packed soil,” says Emilio Miranda, viticulturist with Allied Grape Growers marketing cooperative. “Weed-free vineyards help collect and absorb heat, and the presence of weeds can increase the concentration of bacteria on the crop and increase the potential for frost damage.”
Cultivating prior to a frost event is asking for trouble, he says. Dry cultivated soils have a greater amount of air spaces, which can hamper heat transfer and storage. Wet, packed soil improves the transfer and storage of heat.
San Joaquin Valley growers are beginning the season with good soil moisture and a promising supply of irrigation water, Miranda says.
“Right now, supplies of irrigation water look much better than in recent years. January was pretty dry, but we just had a wet ending for February and are in decent shape water-wise.”
Last month, growers began treating vineyards with preemergence herbicides. Some are finding that several weed species are developing some resistance to glyphosate. In such cases, he says, the key to effective use of the contact weed killer is to apply it early, while the weeds are still very small.
Meanwhile, Miranda sees a need for some measured plantings of new vines in the valley.
“In some varieties, a lot of the vines aren’t as productive as they once were. Also, the market is reaching a point where the amount of new vineyards isn’t keeping up with the rate at which old vineyards are being taken out. We don’t want to see processors looking overseas to fill any shortage that might occur. Of course, we at Allied Grape Growers always recommend planting a new vineyard only after contracting with buyers for the production.”
Although French Colombard, Grenache and Ruby Cabernet have long been popular among San Joaquin Valley grape growers, there’s been a lot of buzz about the idea of planting small amounts of varieties new to the region, such as Cabernet Franc, Malbec, and Petit Verdot, Miranda says.
“Wineries are showing some interest in these non-traditional varieties. But, despite a lot of talk, there hasn’t been a great deal of acreage actually planted. From what we’ve seen, wineries haven’t had much success selling wines from these grapes as varietals. So, they end up being used as blenders, which do not command as high a price. Growers and wineries keep searching for new varieties in the San Joaquin Valley, but seem to keep coming back to the long-established ones.”