Despite continuing concerns over drought, limited availability of water in a number of areas and several heat spikes this spring, it’s been a pretty good growing season so far for wine grape growers in the central and southern San Joaquin Valley, reports Jeff Bitter, vice president of operations for Allied Grape Growers.

Based in Fresno, Calif., Allied Grape Growers is a California wine grape marketing cooperative with nearly 600 grower members in the state’s major wine grape regions.

The San Joaquin Valley crop experienced a run of several 100-degree-plus days in early May and again in early June. As with other crops elsewhere in the state, warm weather throughout the spring has pushed development of the wine grapes in this region about 10 days ahead of their normal rate of development, Bitter notes. Meanwhile, pressure from diseases and insects has been on the mild side.

This year’s AGG’s survey shows bunch counts for most varieties in this area are down from last year. The few exceptions include Chardonnay and Viognier. Bunch counts of red varieties are all down, some as much as one-third, from last year’s numbers.

“Since last year turned out to be a larger than average wine grape crop in central and southern San Joaquin Valley, the decreases in bunch counts could point toward a crop that is closer to average in size,” Bitter says.

Although bunch counts don’t correlate exactly with crop size, they’re the first indication of the potential size of the 2014 crop. Growers will get another clue from the size of clusters after veraison when the berries begin softening and developing sugar. In mid-June, growers were seeing veraison in the earlier ripening varieties, such as Fiesta. By the end of the month, all varieties are expected to be in or through veraison.

However, those observations won’t mean much if growers lack the water needed to finish the crop to match these earlier yield indications.

AGG estimates about a third of the wine grape acreage in central and southern San Joaquin Valley is on the West Side, where growers have received little, if any, surface water this season. The amount of water available for the remaining two-thirds of vines in this region varies, depending on the irrigation district and availability of well water, Bitter notes.

For many growers here, accustomed to producing a crop with the aid of surface water, this is the first season in a long time when they’ve had to rely on their wells to meet much of their water needs. Some, who skimped on well and pump maintenance or failed to upgrade their equipment in the midst of declining water table levels over the years, have seen wells run dry and pumps fail to keep up the pace, he adds.

Earlier this season, AGG was advising its growers to use water prudently to prevent excess canopy growth and, thus, the need to support that foliage with additional water throughout the summer. It continues advising judicious use of water, even as temperatures warm up.

“That means giving vines the water they need during the heat of summer, but not too much,” Bitter says.

One way is to look for obvious signs of over-irrigation, like active growth of shoot tips as summer progresses. “The idea is to encourage canopies to begin shutting down and directing the water to growing and maturing fruit rather than leaves and canes,” he says.

Many AGG growers are also basing their irrigation decision on results of a pressure chamber or pressure bomb test, Bitter reports. A leaf is placed inside the chamber, leaving the petiole exposed through a seal in the chamber. This device applies air pressure to the leaf. The amount of pressure required to cause water to appear at the petiole indicates the degree of tension the leaf is experiencing on its water. The more pressure required, the more water-stressed the leaf. (Details are available on the University of California Fruit and Nut Research his and Information Center website at http://bit.ly/PressureChamber)

Following two record-large wine grape crops, Bitter would like to see prices maintain the levels of the last several years.

Ample inventories of wine for the $7-a-bottle and lower market have helped slow sales of grapes to that segment of the trade, he notes. That’s the same market where many of the wine grapes grown in central and southern San Joaquin Valley are destined. In fact, some growers here have made new plantings of these grapes in the last few years.

The slowing of sales in this market put downward pressure on sales of California wine grapes in general.

“The momentum of the last few years is slowing down and buyers have been pretty quiet lately,” Bitter says. “They’re not going out and actively buying wine grapes in the San Joaquin Valley, and this is acting as a depressant on the market. Wineries have inventory so they are in no hurry to ensure more supply.

“In addition, a very high percentage of grapes are already under contract for 2014 via multi-year agreements. So, there really aren’t a lot of grapes on the spot market to begin with. Because of the water concerns for this year’s crop, buyers don’t want to come out early with too low of a price. With this scenario we’re not likely to see much activity in the market until harvest starts.”

He looks for grape trucks to begin rolling in the central and southern San Joaquin Valley, the last week of July. That would be similar to last year’s July 25 start of harvest.

With growers pulling out an estimated 10,000 acres of Thompson Seedless vines this past winter, the supply of those grapes for both the wine and raisin markets should be down. In addition, bunch counts reported for this year’s Thompson Seedless crop range from about 15-percent to 20-percent lower than last year.

“These factors should translate into higher green and raisin prices for this variety,” Bitter says.