In March — the first time in a long time — walnut grower Paul Stanfield treated his trees to control walnut scale, which was spread pretty much throughout his orchards.
“For the last five years or so, we’ve used insecticide formulations targeted at a single pest, like coddling moth or navel orangeworm,” says the Hanford, Calif., grower. “Prior to that, we had been using broad spectrum chemicals that controlled various types of insects. That’s probably allowed scale and other secondary pests to slowly build up.”
Also, in March, Stanfield sprayed his Vina trees with a fungicide to treat for blight. Summerfield Farms’ 240 acres of walnuts include Chandler, Serr, Tehama Vina and Tulare varieties. Pecan trees are on another 18 acres.
His older trees are planted on a 30 x 30-foot spacing, but when he replaced an old orchard six years ago, he chose a 28-foot equilateral spacing for the new orchard.
“Growing more trees per acre not only increases production, but results in a more uniform tree size, allowing each tree similar amounts of sunlight,” Stanfield says. “I didn’t anticipate these trees growing as well as they have, because they were planted where walnuts had grown before. But, I’ve been really pleased with how they’ve developed.”
Coddling moth and mites are his two biggest pest problems. “Navel orangeworm damage at harvest usually appears in nuts that have been previously infested by the pest,” he explains. “Over the last few years, we’ve found that if we can control coddling moth, harvest in a timely fashion, and practice good winter sanitation in our orchards, we can usually keep navel orangeworm under control.”
He sprays the overwintering generation of coddling moth once in early to mid-May, depending on seasonal flight patterns in the Serrs. Most years, he treats again later in the season. Last year, he applied a second spray on some orchards in June and a third spray in July or around the first of August. He’s even sprayed a fourth time when needed.
“If the coddling moth population is low enough, I’ll skip the overwintering sprays,” Stanfield says. “But, I almost always treat the second generation in the last half of June, when I can also spray for mites at the same time. Normally, that’s the only time I treat for mites, unless there’s a flare-up along dusty driveways. Then, I’ll spray them a second time.”
Timing his irrigations to allow the ground to dry enough to permit spray rigs in for applying for spraying insecticides and herbicides can require some juggling.
He tries to run water every 14 days during the summer months to keep up with the heightened consumption of mature trees. “Our orchards take a good 12 days to dry, and that leaves only a few days to control insects and weeds,” Stanfield says. “But, if we need to get in sooner, I’ll shorten up or extend the interval between irrigations as needed.”
Last year, he began his first irrigations the first or second week of April. This year, as a result of winter and spring rains, he was able to delay the first irrigation until the beginning of May.