California pistachio growers who are planning to shake their trees twice during this year’s harvest should have begun test shaking their trees over the Labor Day weekend, reports Bob Beede, University of California Cooperative Extension Farm Advisor for Kings County. That’s based on what he’s been hearing from growers and would be earlier than normal.
With a two-shake approach, the first shake is a light one and is designed to remove the most mature nuts. “This reduces the navel orangeworm (NOW) threat by removing the nuts most susceptible to NOW damage,” Beede says. “Then, growers will go back a week or two later and shake the trees a second time to get the rest of the nuts.”
Earlier this summer, an unusually high number of early splits occurred compared to recent years, increasing concerns among growers about the NOW threat, he notes.
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It’s not unusual for a very small percentage of pistachios to split prematurely in July. But, this season the increased incidence of “early splits”, coincided with the second NOW generation. As a result, many growers made additional insecticide sprays to help minimize damage.
Meanwhile, near record hot weather in August, particularly on the when temperatures rose as high as 109 degrees in many areas, highlighted the value of timely irrigation throughout the summer in maximizing the number of full, split nuts at harvest.
“University of California research shows that the developing kernel is extremely sensitive to water stress from the time the kernel starts growing, usually around July 1, until harvest,” Beede says. “Proper irrigation management during this period, known as stage 3, is critical to maximizing the percentage of split nuts at harvest.”
This year, irrigation costs for West Side growers have increased due to a reduced supply of surface water. They’ve been paying as much as $350 to $500 per acre foot for supplemental water to meet the four acre-foot per year water requirement of the trees, Beede notes.
As August drew to a close, growers on the East Side of the San Joaquin Valley, where the air is more humid than on the West Side, watched their trees for any signs of Alternaria blight. High relative humidity levels in an orchard could trigger an outbreak of the fungal disease. It can cause leaf drop and a rapid breakdown of hulls, leading to dark staining of the nuts and lower market value.
While the pistachio production isn’t expected to set any records, Beede looks for a respectable crop size, overall. However, yields could vary significantly from one farm to another.
“I’ve seen some orchards where the trees have a phenomenal crop on them, as much as 6,000 pounds of nuts per acre,” he says. “However, others look like they may yield only about 1,000 to 1,500 pounds per acre.
“The knowledgeable growers and producers I’ve talked with are suggesting this year’s California crop could be in the 550-million-pound range,” he says. “With a crop this large, we probably won’t have as many jumbos, the 16/18 sizes, this year and more 18/20s. That will work just fine for meeting market needs.”
With the long hours and strenuous work involved with harvest, Beede reminds growers to be safe in and out of the fields. “When you’re dog-tired and driving home at the end of your shift, it’s especially important to stay alert behind the wheel,” he says. “Harvest is hard enough without losing someone. Equipment drivers have to constantly be looking out for where others are to avoid serious accidents.”