Posts Tagged: Pistachio
Monitor for rodent activity and use bait stations before the growing season to prevent problems, UC ANR scientists recommend.
Roof rats are running rampant in California orchards this year, according to UC Agriculture and Natural Resources scientists.
“In pistachio and other nut orchards, roof rats are burrowing and nesting in the ground where they're chewing on irrigation lines, causing extensive damage,” said Rachael Long, UC Cooperative Extension advisor. “They are also nesting in citrus trees, feeding on the fruit and terrifying field workers when they jump out as people are picking fruit. The chewing pests are also girdling citrus limbs, causing branch dieback.”
Holes in the ground around the base of pistachio trees throughout a Yolo County orchard puzzled the grower.
“We looked for ground squirrels, but never saw any,” Long said. “We set up game cameras, but only got birds and rabbits. We put rodent bait in the holes, but the digging didn't stop.”
Long, the pest detective, cracked the case by consulting Niamh Quinn, UC Cooperative Extension human-wildlife interactions advisor based in Irvine. “She informed us that the damage we were seeing was from roof rats.”
Burrowing roof rats sounds like an oxymoron. While roof rats generally don't burrow in urban environments, their country cousins have been known to burrow.
“It's not true that they don't burrow,” Quinn said. “When I worked as staff research associate for Roger Baldwin, UC Cooperative Extension wildlife specialist, that is mostly what we studied, burrowing roof rats in orchards.”
Baldwin said, “It seems to be a good year for rats in a number of different areas and crops throughout the state. I've received more questions and comments about rats this year than perhaps the last 10 years combined. As for bait application, putting bait down burrow systems for rats doesn't usually work too well, so I'm not surprised that approach didn't work. Growers will likely have better luck with bait stations in the trees.”
Because the rats climb, Baldwin suggests attaching bait stations to tree branches.
“In addition, elevating the bait stations will eliminate access to bait for many protected mammal species, such as kangaroo rats,” Long said. “The bait diphacinone grain can be purchased from some ag commissioners' offices. This is what Roger Baldwin said they tested and it worked.”
As for the bait stations, they should be designed so that there isn't any spillage for nontarget animals to eat, Long said.
When roof rat outbreaks occur, rodenticides are often needed to prevent crop damage. However, timing is critical as diphacinone use is highly restrictive and not allowed during the growing season, which is beginning as the weather warms.
“Check the product label for application instructions,” Long reminds growers. “It's the law.”
Identifying the pest
“Roof rats can forage away from their nest, so you won't likely find signs of their activity, such as rat droppings outside their burrow, to help identify them,” Long said.
Ground squirrels are active during the day, so they are more likely to be seen, dig holes about 4 inches in diameter and forage above ground near their burrows. Vole and mouse holes are 1- to 2-inches in diameter. Roof rat holes are typically 3 to 4 inches in diameter and might have nut shells in front of them, for example pistachio or almond shells. Rabbits will feed on seedling crops, but do not dig burrows.
“Rats are sneaky and hard to spot,” Long said. “If you see damage, including digging in the soil but no wildlife, suspect rats.”
For more information on controlling roof rats, download Quinn and Baldwin's free UC ANR publication 8513, Managing Roof Rats and Deer Mice in Nut and Fruit Orchards at http://anrcatalog.ucanr.edu/Details.aspx?itemNo=8513.
The same approach was used in a long-running battle with pink bollworms, which used to be the bane of cotton farmers. The story said USDA is checking fields this year before declaring pink bollworm officially eradicated.
Navel orangeworm isn't a serious pest of citrus, as the name might suggest, but it is devastating in tree nut production, said David Haviland, the UC Cooperative Extension entomology advisor in Kern County. Navel orangeworm moths lay eggs inside nuts, which mature and eat the nut meat. The cost of dealing with the pest is "huge," Haviland said.
Currently, the best strategy for keeping the pest in check is mummy removal - clearing nuts leftover after harvest.
"On every acre of almonds or pistachios in California, growers will spend two, three, sometimes $400 on an acre just doing what's called mummy removal," Haviland said.
Farmers also use pesticides against naval orangeworm. Haviland said they are expensive and require tedious paperwork.
"If the growers can use the sterile technique to actually avoid pesticide use altogether, that would be an ideal situation for both the farmer as well as for the consumer that's concerned about how their food is produced," Haviland said.
The USDA facility expects to send a shipment of sterile moths to California in August to see how well they disperse.
“Given California's drought and the need to use all available water supplies, even those of marginal quality, there will be great interest in Ken Schmidt's and UC Cooperative Extension advisor Blake Sanden's talks about Valley water supplies and quality,” said Louise Ferguson, a UCCE specialist in the Department of Plant Sciences at UC Davis and organizer of the event.
Sanden, who is based in Kern County, will give a presentation on his research on the effects of using saline water for pistachio irrigation on crop yield and soil quality.
“In 2014, there were problems of fruit set and pollination,” Ferguson said. She expects there will be strong interest in the talk about the effects of climate and other factors on pollination requirements and fruit set by Gurreet Brar, UCCE advisor in Fresno County.
An emerging problem that growers have been seeing in California and Arizona in the past three years is what scientists are calling Pistachio Bushy Top Syndrome in clonal UCB1 rootstocks. Affected trees are short and stunted, have closely spaced internodes, exhibit bushy growth and twisted roots. The cause is unknown, but scientists have found it to be associated with the bacterium Rhodococcus.
Jennifer Randall, a professor in the Department of Entomology, Plant Pathology and Weed Science at New Mexico State University, will deliver the first public presentation of research results on the "bushy top" syndrome.
A full day of research presentations are scheduled.
Themis Michailides, a researcher in the Department of Plant Pathology at UC Davis, will give an update on pistachio diseases.
David Haviland, UCCE advisor in Kern County, Kris Tollerup, UC IPM advisor, and Bob Beede, emeritus UC Cooperative Extension advisor will discuss management of navel orangeworm, Phytocoris, leaf-footed bug and stink bugs.
Brad Higbee, director of entomology research for Paramount Farming Company, will discuss how winter sanitation of orchards can decrease pest pressure and, in turn, reduce the need for pesticides.
Joel Siegel, USDA-ARS research entomologist, will explain how to how to anticipate pest pressure based on past infestation levels.
Patrick Brown, professor in the Department of Plant Sciences at UC Davis, will discuss nutrient management in pistachios.
The 2015 Statewide Pistachio Day will be held from 8 a.m. to 4:30 p.m. at the
Visalia Convention Center. For more information, visit http://ucanr.edu/sites/pistachioday.
For more than 100 years, the University of California Cooperative Extension researchers and educators have been drawing on local expertise to conduct agricultural, environmental, economic, youth development and nutrition research that helps California thrive. UC Cooperative Extension is part of the University of California's systemwide Division of Agriculture and Natural Resources. Learn more at ucanr.edu.
Tension is rising. In these last hot days of August, as the nuts reach maturity, the shells must split. If too many of them don’t, the harvest will be much less profitable, because it’s hard to make a natural-looking split in a pistachio shell with a machine, and unsplit pistachios bring a lower return. Growers are watching the split percentages carefully; wait too long for the highest number and navel orange worms have a larger window of opportunity to lay eggs along the sutures.
Pistachio orchards are harvested mechanically, and the machines are generally owned by contractors, though a large farm may have its own. As soon as the first machine enters the first orchard — the greatest acreage is on the west side of the San Joaquin Valley, around Bakersfield — a race begins.
“It’s chaotic,” says Ferguson. For more than 15 hours every day, beginning before dawn and finishing at dark, the harvesters speed through tunnels of dust and noise up and down orchard rows, followed by bank-out wagons that must get the nuts to the processing plant for drying before the day is out. Each wagon holds 55,000 pounds of pistachios. Left too long in the heat, under the weight of such a load, the pink hulls (each nutshell is within a hull) degrade and stain the shells a darker shade, which lowers the nuts’ value. The California pistachio industry prides itself on producing a large, naturally split, light shelled nut with no artificial splitting or bleaching.
The race gets more fraught each year because contractors have significantly more and more acreage to harvest within the six-week harvest season. Ferguson calls pistachio the “single most successful plant introduction in the 20th century.” The California crop has grown from zero to approaching a quarter million acres in 40 years.
Her colleagues at UC Davis are breeding varieties with a more reliable split and a very early or very late harvest date to spread out the season. Meanwhile, the chaos goes on. This year, because of the cool spring, Ferguson suspects the nuts will split over an extended time period, so growers may well decide to harvest once, then a few weeks later get the harvesters back for a second time.
See a tree shaker harvesting pistachio nuts below. (Video provided by Coe Orchard Equipment.)