Huter Farms’ Thompson seedless vines in the central San Joaquin Valley began blooming at the beginning of May, but like last year, cool spring weather has delayed growth of the raisin grape crop.
“The vine development is about 7 to 10 days behind,” says E.G. Huter, Fresno. In addition to his own 20 acres, he works with his father, Elmer Huter, Jr., in growing another 340 acres of Thompson seedless near Kerman.
As the third week of May began, they had finished their first fertilizer application of the year, treating every-other row with a half rate of UN32 and Asset root stimulant. Next month they’ll apply the rest of the UN32 plus potash on the rows not treated in the first pass.
“This split application seems to strengthen the vines and produce better quality grapes,” E.G. says.
One lesson he has learned since he began growing grapes on his own three years is the value of getting the jump on powdery mildew. “It’s a lot more expensive to fix the problem than to prevent it,” he says.
His program for controlling the disease begins when he sprays wettable sulfur and a strobilurin fungicidewhen the shoots reach eight inches long. Earlier this month he sprayed wettable sulfur for the third time, along with a sterol inhibitor fungicide, foilar fertilizers and zinc.
If needed, he’ll come back 14 to 21 days later with wettable sulfur and a different strobilurin fungicide from the one he used earlier. He’ll make a fifth spray before veraison, applying wettable sulfur and more foiliar fertilizer. Last year, this application also included a sterol demethylation inhibitor (DMI) fungicide.
The Huters use machines to pick and lay most of their raisin crop on continuous trays. The only exception is a few hand-harvested acres, where obstacles like telephone poles and tight turning spaces prevent use of mechanized equipment.
The majority of Huter Farms’ vines are 20 to 30 years old, although in some fields vines have been growing for almost a century. Termites are preventing the old vines from producing to their full potential.
“We have a pretty big problem with termites eating the wood on these vines,” E.G. says. “Termites can be a bigger crop reducer than anything on older vines — eventually the vine succumbs to the damage. The termite-infested vines can also be damaged when picked by machine.”
Instead of layering canes to fill in the voids where vines have been lost due to machine damage, disease, termites or sandy areas, the Huters plant grafted vines — Thompson on Freedom rootstock — in the open spots.
“The grafted vines are more vigorous and produce more grapes, especially in sandy areas,” E.G. says.