The short-term marketing outlook for raisins is anything but cheerful, and even the long-term future of the industry is uncertain at best. Global competition has driven down prices significantly and increasing concerns about labor availability and cost hang over a struggling California raisin industry.

Faced with this uncertainty, Russell Gunlund and his two sons Lance and Gere of Caruthers, Calif., ripped out 191 acres of Thompson seedless vines last winter, invested a little more than $3,000 per acre in an overhead Dried-On-The-Vine (DOV) trellis system, and sank about $2,000 more into the venture to replant the vineyard with Fiesta variety grapes.

“This is the only thing we could do if we were going to stay in the raisin business,” Russell Gunlund says. “The economics just aren't there under the old way of growing raisins.”

DOV systems enable raisin growers to harvest mechanically and eliminate labor-intensive hand harvesting and between-row drying on paper trays. DOV systems also produce higher yields of improved quality raisins, especially with newer varieties.

Commercial adaptation of DOV has been relatively slow, due primarily to the depressed economics in the industry. However, the advantages of DOV are indisputable.

“I would guess there's only about 3 or 4 percent of the acreage that is currently set up for DOV,” says Pete Christensen, retired University of California Cooperative Extension viticulture specialist.

“Eventually, most growers will convert to DOV, but it's not going to happen overnight. More than likely, it will be a long, slow process.”

DOV in its simplest form are vines retrained to accommodate mechanical harvesting with no modifications to the existing trellis system. Tulare County UCCE farm advisor Bill Peacock is currently working on this system which offers growers the obvious advantage of foregoing the need to come up with a large capital investment to convert to DOV. However, there are no significant yield increases to be gained with this system. The same is true for the “South Side” system that utilizes a minor modification in the trellis system to reposition vines for mechanical harvesting.

Easy conversion

“These systems are a relatively easy way for a grower to convert a Thompson seedless vineyard to DOV,” Peacock says. “Under the current economic conditions, that is very attractive to a lot of growers. Even though a grower won't get higher yields under this system, he will get the advantages that go along with mechanical harvesting.”

The open gable system is another DOV option that some growers are installing and using with early ripening varieties such as DOVine and Fiesta. “We are working on the system at Kearney and are getting yields of 3.5-4.5 tons per acre,” Christensen says. “It has the advantage of utilizing all of the existing farming equipment and not requiring any low profile equipment. Also, a grower can install a smaller acreage at a time as each row is free-standing. There are no interconnecting structures like those that are required with the overhead system.

“Also, the trellis and vine structures are lower which facilitates hand labor tasks. In addition, fruit drying is faster than with the overhead. While the system does not appear to be as high-yielding as the overhead, it has advantages in lower start-up and maintenance costs. Its greatest potential is probably for medium-size acreages.”

The Gunlunds considered all of the alternatives, and opted to go with the overhead system and the new varieties. “For our situation, we feel like the future is with the newer, early maturing, higher yielding varieties,” Lance says. “In addition to the late maturity and the lower yield potential with Thompson seedless, there are other drawbacks that a DOV system doesn't necessarily solve. For one thing, I've noticed that those systems produce a lot of unwanted crown fruit. You can't take that off mechanically. It has to be done by hand. As for the late maturity, you can compromise and cut the canes early, but there are obvious disadvantages to that.”

Varieties developed specifically for DOV systems mature about 10 to 14 days earlier than Thompson Seedless. In addition, the differences in yield potential between Thompson Seedless and some of the varieties specifically developed for DOV are nothing short of phenomenal. Trials conducted at the UC Kearney Ag Center in Parlier, Calif., have clearly demonstrated the yield advantages associated with the newer varieties.

High yields

“We've seen some rather high yields with the newer varieties, particularly with the overhead system,” Christensen says. “Trials conducted in 1999 and 2000 with Fiesta grown on an overhead system averaged 5.5 tons per acre. DOVine on the overhead system produced 4.2 tons per acre in 1999 and 6.0 tons per acre in 2000. An experimental variety, C51-110, averaged 6.3 tons per acre during that time period on the overhead system. This variety will probably be suitable for standard or South Side trellising, but its high vigor will likely produce higher yields on the more expansive trellising systems.”

By comparison, traditional tray dried Thompson Seedless raisins average about 2.0 to 2.5 tons per acre. The Gunlunds won't speculate about projected yields from the Fiesta they planted under the overhead system. However, they have several years of experience with a 40-acre block of Fiesta that they planted and grew under a conventional trellis system.

“We think it's premature at this point to make guesses about yield with the overhead system,” Russell says. “We know we can make about four tons per acre with Fiesta under the conventional system. By going to the overhead system, we feel like we'll get better yields because there will be better utilization of light.”

Raisin quality is another benefit to DOV systems. “All raisins that are grown in a DOV system have a meatier appearance,” Christensen says. “They perform better in our air stream sorters and tend to grade better than tray-dried raisins of similar maturity. In addition, rain is not as much of a factor as it is with tray-dried raisins.”

Quieden, a trellising company based in Salinas, Calif., designed the system for the Gunlunds and provided the hardware.

“There are a lot of interesting things about this project,” according to Dan McNamara of Quieden. “First of all, the Gunlunds decided to tackle the role of general contractor. By unbundling, they saved themselves more than $500 per acre.”

Most growers opt for a turnkey operation when installing a trellis system. For the Gunlunds, the hands-on approach seemed to make more sense.

Cheaper, quicker

“We've got labor already in place that we were able to utilize,” Gere Gunlund says. “In addition to the savings, we were able to get the job done a lot quicker.”

The process moved quickly. They started tearing out the old vines in November 2000. Deep-ripping the 191 acres three times and fumigation followed. By March, the interior posts were in place and the vines planted. They used Lopez and Gomez to install the end posts and anchors and made arrangements with various suppliers and installation contractors to complete the balance of the installation. By the end of May the entire trellis system was in place.

One of the most amazing accomplishments that surprised even the Gunlunds was the rate of growth achieved by the vines in the first two months. After a mere eight weeks in the ground, they were emerging from the tops of the four-foot grow tubes. Although common in wine grapes, particularly in coastal areas, large growth tubes are not a common practice when establishing a raisin vineyard.

“Grow tubes got somewhat of a bad rap in the Valley because they weren't done correctly,” McNamara says. “It's very important that you get a grow tube with enough diameter to it, so that it won't restrict the leaves too much while the vine is growing. Additionally, it's very important for the grow tube to be a neutral color so it won't block certain light colors. The material needs to be stiff enough so the tube will not flatten in the wind and rigid enough to be pressed into moist soil to form a seal.”

Quiedan supplied the grow tubes for the Gunlunds.

“Look at this growth we're getting,” Lance Gunlund points out. “In my opinion, these grow tubes have already paid for themselves. Without the grow tubes, we would expect less than half of the growth we've seen so far. I think it's very likely we'll get at least some production out of these vines next year. Not only do we have much better vigor than we anticipated, we haven't spent anything on hand labor to train the vines up to this point. In addition, we can easily keep the vineyard floor clean with a standard herbicide program without harming the vines.”

System features

Some other interesting features to the Gunlunds' DOV system include the use of wooden interior posts and a six and half-foot ceiling for the trellising wires. “In an overhead system, the majority of the weight on the trellising system comes from the top,” Gere Gunlund says. “We're not as worried about loading up one side of the trellis. We can put a lot of weight up here, and this system should be able to hold it without a problem.”

The Gunlund's overhead system consists of a matrix of wires at 6.5 feet above ground. The wires are terminated on cables elevated to 6.5 feet which run around the perimeter of the vineyard.

“We used eight wires per row that run the direction of the vine row,” McNamara says. “These ‘row wires’ are spaced about 20 inches apart and run in the direction of the vine row. Perpendicular wires cross under the ‘row wires’ at every vine, i.e. 6 feet. There is a stake at every vine which supports the ‘crosswire’ which in turn supports the ‘row wires’. The wires provide a matrix which directs the canopy load downward and spreads the weight load throughout the system.”

While most overhead systems are at least seven feet high, the Gunlunds opted to go a little lower. “We decided on six and half feet because it's a better fit,” Gere says. “It's a small detail, but we think it will work extremely well when it comes to any labor requirements.”

Labor issues, in general, will eventually drive the conversion from traditional production to DOV systems, according to almost anyone in the industry. “DOV doesn't necessarily reduce overall labor requirements, but it enables a grower to utilize labor more efficiently,” Christensen says. “It's easier to manage because that need is spread throughout the entire season instead of having it concentrated at harvesttime. So far, we've been able to cope with the challenges of finding labor at harvest, but it's getting more difficult every year. Over time, it will likely become even more challenging.”

Labor needs spread

With a DOV system, labor requirements are transferred from harvest to other operations such as vine training, cane cutting and canopy management that take place throughout the season.

“This works extremely well for us,” Russell Gunlund says. “We already have permanent labor in place. Now we have something to keep them busy throughout the entire year, instead of having peak labor requirements at harvest. That situation has been getting more difficult to deal with every year. We've got labor contractors now who are making unreasonable demands, telling us when we can harvest our grapes and threatening us with a shortage of labor if we don't follow their schedule. I can't tell you how irate that makes me. With this system, we'll definitely get rid of that headache.”

The capital investment for converting to DOV can range from practically nothing for Peacock's system to thousands of dollars per acre depending upon the trellising system selected and the method of installation.

For growers who decide on the overhead system, the rewards could be huge, but only time will tell. “If you can make 6 1/2 to 7 tons of raisins per acre, you can pay for a trellis system in a hurry,” Peacock says. “You just have to have the money to invest in it, or at least enough guts to go borrow it.”