Posts Tagged: pistachios

A hike in navel orangeworm pressure expected later this century due to climate change

Outsized wildfires, rising sea levels and disappearing glaciers are dramatic signs of climate change, but not the only ones. New UC Agriculture and Natural Resources research provides forewarning of a change that will be economically and environmentally costly to California – a fifth generation of navel orangeworm, the most destructive pest of almonds, walnuts and pistachios.

Navel orangeworm (NOW) will be more problematic in the future because of warming temperatures, UC Cooperative Extension scientists report in Science of the Total Environment.

Like most insects,NOW's development rate, physiology, behavior and reproduction are highly dependent on the ambient temperature. When the weather warms in the spring, NOW moths emerge from the nuts left in the tree or on the ground during the winter. After mating, females then recycle those last year's nuts to lay eggs and complete one generation. Adults emerged from that first and subsequent generations then lay eggs on in-season hull-splitalmondnuts, where larvae feeding damages the crop. Typically the pests fly three to four times per year – with more flights in areas with warmer weather.

“Warmer temperatures can result in early activity of the pests in the spring and increased activity during the season,” said Tapan Pathak, the UC Cooperative Extension climate change specialist and the study's principle investigator.

The scientists looked at 10 climate models to determine what nut farmers can expect to face over the next 80 years and applied NOW developmental models to the changing climate. Daily maximum and minimum temperature data were obtained for 1950 to 2005, and future projections stretched to 2100.

“The fifth generation can happen in the next few decades,” said Jhalendra Rijal, UC integrated pest management advisor and co-author of the research. “The climate models suggest that spring will begin earlier. That causes insect activity to start earlier. With increased temperatures through the season, the number of days to complete a generation is less. At the end of 2050 or so, we'll see an extra generation.”

The study focused on 23 counties in the Central Valley, from Shasta County in the north to Kern County in the south, where 1.78 million bearing acres of nut crops are planted. About two-thirds of that acreage is planted to almonds, 20% in walnuts and 16% in pistachios. The tree nut crops were valued at more than $8 billion combined in 2018, according to the California Department of Food and Agriculture.

The completion of the NOW life cycle is faster in pistachio compared to almonds and walnuts, so the potential risk of crop damage and economic loss is higher in pistachio, according to the research report. There are only a few years historically in which the models detected the fifth generation of NOW in Kern County pistachios. The occurrence of the fifth generation in almonds and walnuts was historically nonexistent, but it starts appearing in three southern counties by 2040 and eleven counties by 2100.

“In order to alleviate some of the risks related to navel orangeworm damage to nut crops, it is important to implement integrated pest management practices,” Pathak said.

IPM preventative and control measures include sanitizing the orchard during the winter by removing all the nuts on the ground and in the trees, applying synthetic reproductive hormones to limit the pests' ability to find mates, encouraging natural enemies, judicious of least-toxic pesticides if necessary and harvesting the crop early to avoid a new generation of the pest.

“A better understanding of future navel orangeworm pressure on California's major nut crops can help facilitate and strategize integrated pest management practices in order to minimize production risks,” Pathak said.

The results of the research can also inform growers and pest control advisers about the potential increased threat from other pests as the climate changes.

Climate and California agriculture of the future

One of the forces driving agricultural experiments in California's fertile San Joaquin Valley is climate change, reported Mark Schapiro on Grist.org. Although some sources still don't feel completely comfortable with the concept.

"Whether it's carbon built up in the atmosphere or just friggin' bad luck, the conditions are straining us," said John Duarte, president of Duarte Nursery.

The state's fruit and nut orchards are taking the most heat as conditions change. A fruit or nut tree planted today may be ill-suited to climatic conditions by the time it begins bearing fruit in 5 or 10 years. Between 1950 and 2009, “chill” hours trees needed annually to reboot trees' metabolic system for the spring bloom had already declined by as much as 30 percent, according to a California Department of Food and Agriculture study.

“If trees haven't had that low-chill period when they wake up in the spring, it's like being up all night and then trying to go to work.” said Mae Culumber, a nut crop advisor with UC Cooperative Extension in Fresno County.

Researchers have already observed that cherry, apricot, pear, apple, pecan and almond trees are often less productive than they used to be.

The article said farmers may turn to pistachio trees to weather a warmer and dryer California. Pistachio trees require one-third to one-half as much water as almond trees. During droughts, pistachio tree metabolism slows and when water returns, they start producing nuts again. And they can produce nuts for 80 years or longer, almost four times the life span of an average almond tree. 

For field crops, scientists are looking at improving the soil and transforming growing systems to help farmers adapt to the warming climate.  

“When I drive to the Central Valley, I get goosebumps; I feel the urgency,” UC Davis agronomist Amélie Gaudin said. “I see an agriculture that is basically hydroponics. It's like a person being fed/kept alive by an IV.”

“What happens when you no longer have the sugar-water?” she adds.

Gaudin is focusing on using agroecological principles to develop efficient and resilient cropping systems. Planting cover crops and reducing tillage show promise for mitigating the impact of climate change in the valley.

Too many California pistachios coming up empty

Some California pistachio farmers are facing one of their worst harvests ever, reported Sarah Zhang on Wired.com.

UC Agriculture and Natural Resources experts said the dip in yield cannot be blamed on the drought, but a warming climate may be coming into play. Pistachios require cold winter temperatures to reset their biological clocks.

“They use the temperature to know when winter is over,” said Craig Kallsen, UC Cooperative Extension advisor in Kern County. “And if they don't get the message, they get confused.”

Male trees then end up blooming after the female tree. If female plants don't get fertilized when they bloom, they still produce shells—just empty ones. 

Kallsen said the hardest hit regions are in the Southern San Joaquin Valley.

"We're looking at a record low (yield)," Kallsen said.

Farmers to the north had more chilling hours, so they are seeing a normal or low number of empty pistachio shells.

Growers have found that spraying oil can help trees bloom more uniformly, however, it doesn't always seem to help, the story said.

“There are a lot of things we're still trying to understand,” said Gurreet Brar, UC Cooperative Extension advisor in Fresno County. “Oil applied at the wrong time or in inappropriate conditions like water stress conditions can injure the plant.” 

Pistachio crop threatened by fungus

The California Report, a popular radio news program that is broadcast throughout the state on public radio stations, devoted five minutes this morning to a solution found at the UC Kearney Agricultural Research and Extension Center for a serious pistachio production problem.

Reporter Alice Daniel interviewed Kearney-based UC Davis plant pathologist Themis Michailides, who led the team that discovered how to expose pistachio trees to spores of a beneficial fungus that displaces the fungi that produce aflatoxin.

Though the story was broadcast this morning, it can still be heard on The California Report website and is embedded below:

For more information on the beneficial fungus, AF-36, which was used for the first time in commercial pistachio orchards this past summer, read Pistachio farmers enlist a beneficial fungus to battle aflatoxin.

California nut harvest winding down

Nut harvests in California are winding down, and growers of almonds, walnuts and pistachios are mostly happy with their yields, reported Tim Hearden in Capital Press.

• Almond growers expect to meet an early estimate of 1.95 billion pounds statewide, which would be a record


• Pistachio growers in the San Joaquin Valley are enjoying their second-largest crop ever after last year's record yield


• Walnut growers expect this year's yield to be 485,000 tons, slightly lower than last year's 503,000 tons

"The rumors I've heard is that guys are still complaining about the quality" of walnuts, said Rick Buchner, a University of California Cooperative Extension farm advisor in Red Bluff. "We're getting a lot of black husks on them, so there's a suggestion that we may have some husk breakdown and husk fly problems. It's probably too soon to tell yet."

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