Posts Tagged: Almonds

Climate change to drive surge in insects that attack almonds, peaches, walnuts

UC study predicts three major pests to emerge earlier, produce more generations

As a result of climate change, the Golden State's farms are expected to face a surge in agricultural pests, which poses a threat to California's specialty crops industry. Populations of three major insect pests – codling moth, peach twig borer and oriental fruit moth — are projected to increase mainly due to rising temperatures, according to a study recently published in the journal “Science of the Total Environment” by a team of researchers at University of California Agriculture and Natural Resources and the U.S. Department of Agriculture California Climate Hub.

“These three pests are notorious for infesting most of the walnut, almond and peach orchards of California, causing extensive damages by reducing quality of fruits and nuts,” said study co-author Jhalendra Rijal, UC Cooperative Extension integrated pest management advisor and entomologist for Stanislaus, San Joaquin and Merced counties.

Climate change can lead to shifts in the timing of seasons, including warmer winters, earlier springs and hotter summers, and these conditions can disrupt the natural life cycles of pests.

 The California research is supported in part by USDA's National Institute of Food and Agriculture. NIFA National Program Leader Amy Ganguli said the California project is a strong example of the  work being done through AFRI's Extension, Education & USDA Climate Hubs Partnership.

 “A key element of this grant program to link critical research findings like this with timely education and outreach efforts to producers and the public to encourage nimble responses to the challenges climate change pose,” Ganguli said.

The new research, led by Prakash Jha, UC Agriculture and Natural Resources assistant project scientist based at UC Merced, compared pest populations in recent and future climates. The scientists used temperature projections from the latest generations of scientific models to predict the potential impact of climate change on codling moth (Cydia pomonella), peach twig borer (Anarsia lineatella) and oriental fruit moth (Grapholita molesta). Before using the model, the model predictions were verified using field data of these insect pests from various parts of the Central Valley.

The UC study revealed that due to increases in temperature, these insects are expected to appear up to 28 days earlier in the spring and the time between generations is expected to shorten by up to 19 days. The changes may be gradual, but the study predicts that we may see up to a half-generation of these pests added within the next 20 to 30 years.

The increase in these pest populations poses a serious threat for future pest management, which would subsequently affect the state's economy and employment related to specialty crops, warns Rijal.

“Codling moth is the primary pest of California's walnuts, which occupies over 365,000 acres,” Rijal said. “Similarly, peach twig borer and oriental fruit moth are two major economic pests of peaches. Growers must control almost every generation of these pests to protect the fruit.

“Additional generations of these pests within the same growing season will likely increase crop damage. It certainly increases the number of sprays needed to control these pests, increasing the production cost for growers. Plus, more use of insecticides has consequences for beneficial insects and the environment.”

Growers may need to adapt their pest management strategies to address the impact of climate change on these pests. 

For years, the UC Integrated Pest Management guidelines have suggested putting oriental fruit moth traps out in peach orchards by Feb. 15 in the San Joaquin Valley and Feb. 20 in the Sacramento Valley.

“In the last seven years, likely due to warmer winter, as suggested in this study, we observed the beginning of the moth's activity in traps (also called biofix) as early as Feb. 14,” Rijal said, “meaning that the trap placement date must move earlier to capture the first moth activity. We are revising the guidelines to change the trap placement date to Feb. 7 for the entire Central Valley.”

Developing a holistic climate-smart pest management strategy will build resilience, Jha said. This approach combines pest control with prevention and reduction, such as planting pest-resistant crop varieties, sanitizing the orchards during the winter, harvesting early to avoid later pest generation infestation, using biological control such as natural enemies, and deploying mating disruption techniques.

“More importantly, adoption of pest forecasting – including the long-term prediction and short-term potential outbreak, pest-scouting and early detection – will be essential to combat the growing threat posed by these pests,” Jha said. 

Research will be crucial to provide growers support and guidance about the latest developments in pest management and how to adapt their practices.  

“Climate change impacts on pests and resulting impacts on agricultural production are significant but not often researched or quantified,” said Tapan Pathak, UC Cooperative Extension specialist in climate adaptation in agriculture based at UC Merced.

“Information from this research will not only help farmers to understand impacts for strategic planning, but also will inform the agricultural industry to invest in making varieties more resilient to these damaging agricultural pests,” Pathak added. “We will use this information to update the CalAgroClimate tool, which informs farmers on the progress of these pests during the season so that they can take steps for effective pest management.”

Ganguli added the partnership between the University of California and the California Climate Hub embodies the goal of this funding program.

“The incorporation of this research into the existing CalAgroClimate decision support tool accelerates the ability of this information to be publicly used in the development of appropriate pest management or adaptation strategies,” she said.

In addition to Jha, Rijal and Pathak, the study was co-authored by Ning Zhang, Lauren E. Parker and Steven Ostoja of UC Davis Institute of the Environment and U.S. Department of Agriculture California Climate Hub.

The article “Climate change impacts on insect pests for high value specialty crops in California” can be accessed for free online at https://doi.org/10.1016/j.scitotenv.2023.167605.  

Dec. 8, 2023: This story was updated to add comments by NIFA National Program Leader Amy Ganguli.

 

 

 

Winter atmospheric rivers gave pathogens, diseases path to infect crops

Outbreaks similar to El Niño-influenced issues of the 1990s

The wave of atmospheric rivers that swept across the state this winter has created the right conditions for plant pathogens that haven't been seen for decades in California. University of California, Davis, plant pathologist Florent “Flo” Trouillas is getting more calls from growers and farm advisors concerned about potential crop damage.

“Generally, whenever you have rain events, you're going to have problems,” said Trouillas, a Cooperative Extension specialist who is based at the Kearney Agricultural Research and Extension Center in Parlier. “In wet years we get really busy because most pathogens need and like water.”

Trouillas is like a disease detective. He splits his time between the field and the lab, working to diagnose pathogens, diseases and other ailments that strike fruit and nut crops such as almonds, cherries, olives and pistachios.

On a recent visit to an almond orchard near Fresno, Trouillas joined Mae Culumber, a nut crops farm advisor for UC Cooperative Extension Fresno County. A few weeks earlier, the two had walked the orchard, taking note of the base of some trees that had gumming — a thick, jelly-looking substance indicating a pathogen had taken hold.

“A lot of what Florent is doing is trying to assess patterns on a landscape,” Culumber said. “Sometimes things may look like they are one thing, but it could be another problem.”

When the two returned weeks later, the amber-colored gumming had moved into the canopy, looking like gumballs stuck to branches, some of which were already dead. “It's getting out of control from before,” Trouillas says. “This branch was killed. This is widespread.”

From the field to the lab

Lab testing confirmed what Trouillas believed was the culprit: Phytophthora syringae, a pathogen that can affect almond crops but is rarely seen in California. If it is found, generally the site of infection are wounds caused by pruning, but that is not the case here, where the infection began in the canopy at twigs, or small branches.

It is a threat to a key crop, which according to the California Department of Food and Agriculture, generates $5 billion annually. The last time Phytophthora syringae hit California was in the 1990s after a series of El Niño-influenced storms. Trouillas, who has a photographic memory, remembered reading about it in an old manual.

“It's rare for California and one that we see mostly following atmospheric rivers,” he says.

“The disease will only happen following these extremely wet winters.”

Phytophthora is soilborne, mostly found in tree roots, and doesn't generally spread up into branches. But the intense storms created the right conditions for the pathogen to “swim” up trunks as winds blew spores into the air and rain dropped them back down into the canopy, Trouillas said.

Some of the trees in this orchard will die; others can be saved by pruning infected branches and applying a recommended fungicide, he said.

Identification, diagnosis, education

Trouillas is one of more than 50 Cooperative Extension specialists at UC Davis and each is charged with identifying problems and developing solutions for those issues in support of agriculture, the ecosystem and communities throughout the state.

In his role, Trouillas focuses not only on pathology and research but also on educating growers, nursery staff, pest control advisers and others in agriculture about ways to manage potential threats and how to prevent crop damage.

“His role is very crucial,” said Mohammad Yaghmour, an orchard systems advisor for UC Cooperative Extension Kern County. “He's not only on this mission to educate growers but he's also a source of education for us.”

Trouillas typically conducts one or two site visits a week, usually after a farm advisor reaches out about a problem they can't solve on their own.

“This allows us to be at the forefront of disease detections in California,” he said.

He likens these visits to house calls a doctor would make, only to fields instead. And one of those calls recently took him to a cherry orchard in Lodi.

“These guys help me quite a bit,” said Andrew Vignolo, a pest control adviser with Wilbur-Ellis who asked for a consult. “I bug them a lot.”

The visit starts like any consult in a doctor's office, only the questions come fast as they walk around the Lodi orchard where branches are dying, there is gumming and the trees appear stressed. Some look to be sunburned from exposure. Old pruning wounds show cankers, indicating that past disease treatments didn't get rid of whatever was affecting the trees.

Trouillas asks about the cultivar of the trees because some varieties are more susceptible to pests or diseases. He focuses on stress because that opens the door to disease.

Do they prune in the dormant winter months or in summer when pathogens are more prevalent? Does the soil get tested? How old are the trees? What about nutrition?

“I'm trying to figure out how they got infected so bad,” Trouillas said, walking the orchard. “Bacterial canker is a very mysterious disease.”

He thinks it might be a bacterial canker disease and shaves some bark to take to the lab for testing. He wants to come back next winter to take some samples to see where the pathogen is overwintering.

“We'll know in a few weeks if we have a fighting chance,” Vignolo said.

Be it Lodi, Fresno or elsewhere in the state, Trouillas focuses on local conditions. But what is learned in one field can be passed on to others, providing early warnings or advice for those in similar situations. “All these efforts at collaboration, from the field, to the lab, going through research projects, there's only one goal here — to help the farmers of California.”

Climate change may reduce frost damage to orchard crops

CalAgroClimate web tools help farmers prepare for frost events

A cold snap damaged almond blossoms across the Central Valley, resulting in more than $44 million in crop insurance claimsin late February 2018. A multi-day frost event wiped out roughly 75% of California's citrus crop and severely damaged avocados in January 2007. Frost can damage crops, impact growers' bottom lines and drive up food prices for consumers. With advance notice, farmers may be able to use heaters, wind machines, irrigation and other tactics to lessen some of the impacts of cold weather, such as damaging near-ripe citrus fruit or killing the bloom in almonds.  

CalAgroClimate is a new farmer-focused website that can help growers anticipate weather-related risks and make plans for taking defensive action. Growers and crop consultants can use CalAgroClimate's crop and location-specific tools and resources to help prepare for upcoming frost events. The website's tools can also support on-farm decisions for managing heat, crop development and pests. 

Future holds less frost

The risk of frost damage to crops and the need to prepare for that risk is top-of-mind for many farmers today, but will it always be so? To examine what climate change might mean for future frost risk, researchers at UC Davis, UC ANR and the USDA California Climate Hub conducted a study examining the incidence of temperatures below multiple “frost thresholds” during the months of critical development phases for three frost-sensitive California crops: almonds, avocados and navel oranges.

The researchers found that even during the coldest winters and springs, the incidence of frost exposure declined under projected mid-21st century climate conditions by more than 50% for almonds and oranges, and by more than 75% for avocados. While farmers in 2050 will not find frost risk to completely be a worry of climates past, they will not have to contend with the same frost concerns that farmers face today.

Beyond the obvious benefits of reduced risk of crop damages, additional benefits of reduced frost exposure include lower water use and energy costs associated with mitigation actions. Irrigation is a primary means of protecting crops from frost temperatures, and with fewer hours below freezing that means fewer hours of running water and using pumps. The authors of the future frost exposure study showed that growers may collectively save tens of thousands of acre feet of water and enjoy millions of dollars in energy savings.

Few aspects of climate change are considered “positives,” and although the warming winters and springs that result in reduced frost temperatures could also come with increased pest pressure, reduced chill accumulation and other challenges, the reduction in frost exposure is a silver lining.

However, until this frost-free future arrives, growers still need to be prepared to protect their orchards from frost. To assess frost risk for the next seven days for your location, check out the new interactive Frost Advisory Tool at CalAgroClimate.org.

Five questions with food safety expert, new AAAS Fellow Linda Harris

Professor of Cooperative Extension shares career story, appreciation for UC Davis

After growing up in northern British Columbia, in a remote smelter town called Kitimat (“an 8-hour drive from the nearest McDonald's”), University of California Professor of Cooperative Extension Linda J. Harris embarked on an academic journey that crisscrossed North America and eventually led to her election as a Fellow of the American Association for the Advancement of Science.

AAAS, the world's largest multidisciplinary scientific society and publisher of the journal Science, recently announced the election of its 2021 class, which will be inducted during its annual meeting, Feb. 17-20.

In addition to Harris – a faculty member in UC Davis' Department of Food Science and Technology – four other UC Agriculture and Natural Resources affiliates will be inducted: Helene Dillard, dean of the UC Davis College of Agricultural and Environmental Sciences; Kathryn Uhrich, dean of the UC Riverside College of Natural and Agricultural Sciences; and UC Berkeley Professors Rodrigo Almeida and Paolo D'Odorico.

Harris, a Certified Food Scientist, recently shared her thoughts on the value of extension work, her contributions to the field, UC Davis' support for women in academia, and the arc of her career journey.

How did you get your start in food science and microbiology?

I was interested in science at an early age. As an undergraduate student at the University of Victoria in Victoria, B.C., I enrolled in biochemistry at the suggestion of my high school biology teacher. In my second year, I switched to the University of Alberta in Edmonton, Alberta and decided to review the course catalog – a paper version! When I got to the section on Food Science, the applied nature of the field just sounded right and I never looked back.

However, I didn't do particularly well in microbiology as an undergraduate student – too much memorization for me. At the end of my B.S. I was ready for a job in the food industry and took the very first job I was offered – ironically enough as a dairy microbiologist in a quality control lab. Thankfully, that job opened my eyes to the possibilities in microbiology. What was memorization turned into something I learned through doing and I was hooked.

Two years later, I was ready to go back to school and contacted a professor of food safety microbiology at the University of Alberta who fortunately had funding for me. During my M.S. degree in food microbiology, he encouraged me to pursue the Ph.D. – which was not something I had ever considered – and that led me to leave Canada and head to North Carolina State University and a Ph.D. in microbiology in the Food Science Department, where I worked on a project related to the fermentation of sauerkraut.

I did have one publication related to food safety during my time at NC State, and when I took my first faculty position back in Canada [University of Guelph in Ontario] I continued to work in food safety, mostly with meat and meat products.

I am so glad that I saw the advertisement for my current position and that I followed my instincts to apply for the job. The opportunities to grow professionally and to work in the food safety area at UC Davis, within the Cooperative Extension network in California, and with collaborators across the U.S., and around the world, have been enormous, and I am extremely grateful for the path that led me here.

February 11 is the United Nations-designated “International Day of Women and Girls in Science.” How has UC Davis supported women in your scientific field?

My career in STEM [science, technology, engineering and math] has been very rewarding and many of the gender barriers I faced early on have been addressed. I feel very fortunate to have landed at UC Davis and I am thankful that there is a long history of addressing these barriers at this institution.

When I was hired in 1996, the Department of Food Science and Technology was about 25% women and both the department chair and dean of the college were women. I had never been in a department or college with so many women faculty, including in positions of leadership. It was a very important consideration in my move. Today our department is 50% women and I proudly served for five years as the second woman department chair, from 2016 to 2021.

As a first-generation university graduate raised by a single mother, you have a unique perspective in encouraging young people on their path toward a STEM career. What advice do you have for them?

To those contemplating a career in STEM, I would say: be open to new opportunities and adventures – you never know where they may lead you. Get involved in leadership in any capacity you can from student organizations or around other things that interest you. Skills that you learn with these types of activities will be invaluable to your career.

I am very much an introvert and had to work hard to overcome my fear of public speaking. In addition to leadership roles in student clubs, I joined Toast Masters while working on my Ph.D. These activities had a huge impact on building my confidence and helped influence my career choices.

In the AAAS Fellows announcement, it says you were elected for “contributions to the field of food safety microbiology, especially related to control of Salmonella and other pathogens in low-moisture foods and fresh produce.” Is that your proudest achievement in the field?

I am most proud of the work described by that short statement especially as it applies to California-grown commodities. I would say that my laboratory is best known for work with the tree nut industry – almonds, pistachios and walnuts, as well as a range of types of fresh produce grown in this state.

My laboratory has worked to understand behavior, movement, prevalence, and especially control of foodborne pathogens like Salmonella during production in the field through harvest and postharvest handling all the way through to consumer practices.

I have been fortunate to have many terrific state, national and international collaborators and an outstanding group of people working in my laboratory as we set the foundation for some of the food safety research in tree nuts and produce. It has been most gratifying to watch the significant growth in these fields of investigation, especially with a new generation of scientists that span the country and beyond.

Another “hat” you wear is UC Cooperative Extension specialist. How have you contributed to food safety knowledge and practices in our communities?

I think you will see that my “hats” are not that different. The research from my laboratory has provided the foundation for several commodity-based, food-safety risk assessments – for almonds, pistachios, and walnuts. And these, in turn, have been used in support of regulations or helped guide implementation of safer food industry practices. Our research has also informed several publications aimed at consumer handling of fresh fruits and vegetables and has been cited in regulations pertaining to fresh produce safety. It is gratifying to see our research being used.

My research and extension work are very integrated. One feeds the other. Because I have been able to interact with stakeholders (especially integral to my position as a Cooperative Extension specialist), I have been able to understand firsthand some of the pressing food-safety issues and challenges in California. These stakeholder interactions have largely formed the basis for most of my research and extension grant proposals over the years. The collaborations that have resulted from extension activities have opened doors and access to many unique opportunities for sample collection and research exploration.

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.

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