The third week of August marked the start of the 2015 harvest for California’s raisin grape growers. 

“Just about everyone around here started picking grapes then,” says Dennis Wilt, D&J Farms, Biola, Calif. “That’s two weeks earlier than usual. It looks to be a nice crop, not a bumper crop but average size or better.”

The early harvest is in line with the crop’s rate of growth throughout the season. That includes flowering when Wilt applied his bloom spray of gibberellic acid – to improve grape maturity and raisin grades by thinning berries and increasing berry size – and fungicide about two weeks ahead of his typical timing.

He grows 200 acres of raisin grapes, mostly Thompson Seedless plus some Zante currants, and uses various methods of harvesting them.

After cutting the canes on his 50 acres of dried-on-the-vine grapes on August, he’ll wait about seven to eight weeks for them to dry down to the desired moisture level of 11 to 12 percent before he harvests them by machine.

Meanwhile, Wilt began hand-picking the 50 acres of grapes he dries on individual trays on August 23. The next day he started cutting the canes on the 100 acres of grapes which he’ll harvest 10 to 14 days later by machine and lay on continuous drying trays

He likes to pick his tray-dried Thompson Seedless grapes with sugar levels in the range of 21º to 23º Brix. However, he starts his DOV harvest when the grapes reach 18º to 20º Brix. “When I cut the canes when these grapes have 2 percent to 3 percent less sugar than my hand- or machine-picked grapes, I end up with about 10 percent B and better grades on my raisins,” Wilt says. “I don’t know why. It just happens.”

Wilt doesn’t foresee any problems getting the labor needed to complete this year’s raisin grape harvest. “Because it started so early, crews should be able to get around to everyone in a timely manner,” he says.

This year’s crop has also been favored by the lack of any extended spells of really hot weather. “We only had a day or two when the temperature rose to around 108 to 110 degrees,” he says. “The latest forecast predicts temperatures no higher than about 85 to the low 90s through September. So, we shouldn’t have any excessive heat through harvest.”

If all goes well, Wilt expects to have his tray dried raisins safely inside bins by Sept. 20. In some years, that date can be significant. It’s the deadline when grapes must be picked and laid on drying trays to qualify for any rain insurance benefits.

While harvest prospects look bright, the water situation remains bleak. Except for one delivery of surface water in late June and early July, growers in his irrigation district have relied on groundwater to irrigate their fields.

“The water table is dropping relatively fast because everyone is using well water this year,” Wilt says. “It’s not a pretty picture.”

Three years ago his water table stood 40 to 45 feet below the surface. It’s since declined to a depth of around 80 to 85 feet. Earlier this year, a well on some rented land had to be deepened to 200 feet. That was when the bowls began sucking air just three months after they had been lowered from 70 feet to 85 feet.

“It’s about a one-year wait around here to get a well drilled,” he says.

The quality of the water he’s pumping from the ground is another concern. He’s starting to pick up levels of boron and salts that he hasn’t seen before.

Except for one field which he sprayed to treat for mites and another to control leafhoppers in late June, insect pressure in his vineyards has been light this year, he adds.

“If it wasn’t for the drought concerns, this has been a decent season for growing grapes in terms of weather, insect and disease threats,” Wilt says. “It takes a lot more time and planning when you’re irrigating just 10 acres a day using well water than when I could irrigate 30 to 40 acres in a day with district water.”