In early April, raisin grower Mike O’Brien’s Thompson seedless and Selma Pete vines in Fresno County were showing young growth — a little later than usual for his 40-acre vineyard near Selma, Calif.
O’Brien has been farming his own grapes for 26 years, and he tends the 120-acre raisin vineyard of his father, Larry. The grapes in both vineyards are hand picked and dried on individual trays.
In March, temperatures in Mike’s vineyard dipped to the 29 degree to 30 degree range for several mornings just as buds had started pushing. “I don’t know of any damage,” he says. “It looks like most of the buds will open up.”
Not long after that, as some vines were just sporting their first leaves, hail hit on his vineyard. “It was just a touch of hail, which bruised a few leaves,” he says. “At this point, those vines are looking pretty good.”
That’s far different than last year, when hail fell on his vineyard in March. Then, however, vine growth was farther along and the amount of hail — 2½ to 3 inches in diameter — was much heavier. He lost about 30 percent of his bunches to that storm.
This year’s storm brought badly needed moisture. Soil moisture levels have risen significantly following about 2 inches of rain from the middle of January until mid-March. That followed an exceptionally dry spell.
”When I drove through the vineyard in December and early January, the dust was like it usually is in June,” O’Brien says. “I’ve never seen that kind of dust here in late fall and early winter.”
In fact, in December he irrigated his Harmony rootstock. “It doesn’t like dry roots,” he says.
He irrigates vines with both drip and furrow, using district and well water. Surface water availability this season is questionable.
“Things are pretty slim,” he says. “We haven’t heard yet if we’ll get any water this year from our local irrigation district — it depends on the snowpack. I hope we get at least one release of water.”
O’Brien has completed berm sprays to control weeds and worked up ground and set furrows for running water to protect against frost. He will apply sulfur to protect young growth against powdery mildew.
“We want to knock out that disease early to keep it from getting out of control,” he says.
Last season’s wet, cool weather encouraged unusually heavy powdery mildew pressure. “We used more fungicide last year than we ever have,” he says.
He starts his control program with micronized sulfur. “The liquid adheres to young shoots and leaves and gets into the crown of the vines better than dust,” he says.
After vines have put on more foliage, he’ll switch to sulfur dust.
Vine mealybug has become a threat to O’Brien’s crop only in the last four or five years. At first they were spotty and he treated accordingly. For the past two years, though, he’s treated all of his vines. He’ll begin treating this year, probably around the end of May or early June, after weather warms and mealybugs emerge from the ground.
“We hit them when they come up the vine,” he says. “Treatment is very expensive.” He’ll continue treating, as needed, until harvest. “We’re still learning the best way to control mealybugs.
“Right now our vineyards are looking good. It looks like prices will be up this year, so if we can get our grapes harvested, it should be another good year for us.”
However, hand harvesting and drying before rains come continues to be a challenge for the O’Briens and other raisin growers.
“Last year, we got our grapes harvested without any labor problems,” he says. “But, one neighbor who had decent production was unable to get his raisin grapes harvested. The crews came in, but because weeds in the vineyard slowed them down, they walked off to work in clean vineyards where they could pick grapes faster and make more money.”
To get a jump on raisin harvest and reduce competition for labor at the peak of the harvest season, Mike and his father continue to replace their Thompson Seedless vines with Selma Pete, which matures about three weeks earlier than Thompsons. About a third of their combined acreage is now planted in Selma Pete vines, Mike says. And that proportion will increase.