Posts Tagged: agriculture

Care of Fire or Frost Damaged Trees

Recent and recurring fires are a problem where both citrus and avocado are grown in California.The winter forecast is out from NOAA and it looks like there might be frost in our future.  What do you do if it hits your trees? https://www.noaa.gov/news-release/us-winter-outlook-warmer-and-drier-south-wetter-north  Treatment of damage to both trees by fire and frost is often the same.  Wait.  Wait for the tree to tell you the extent of the damage.  If it's a young tree with mainly green tissue, it becomes apparent pretty soon after the event, within a week to 10 days. With older trees, though it takes longer.  With citrus if there is significant damage to the trunk, it's not likely to recover, or recover to commercial status.  if it's just damage to the canopy, there's a good chance both trees will recover. If there is damage to the trunk of an avocado, though, it is amazing in its ability to recover.  And waiting for up to a year may be necessary to truly evaluate recovery.

Care of Frost/Fire Damaged Trees

Determining the amount of damage is often a difficult job and cannot be done accurately for some months following the freeze. It is usually better to let the tree recover by itself.

Sunburn prevention

Exposed limbs can be badly damaged by sunburning. Whenever defoliated trees have not grown enough new leaves to protect the limbs before hot weather occurs, you should provide protection.

Protection is best provided by spraying or painting all exposed limbs with either a cold-water white latex paint or a whitewash. The paint needs to be white enough to reflect the light, but thin enough to flow through a sprayer. With latex paint, a 2-part latex to 1 part water is usually adequate.

Irrigation

Do not irrigate damaged trees until the soil in the root zone approaches dryness. The loss of leaves reduces the use of water so the soil will remain wet longer than with unaffected trees. Careful, frequent examination of the soil is necessary to prevent excess moisture from normal irrigations. Root Rot occurs in soils with excessive moisture when the Phytophthora fungus is present, and growers must guard against this disease following frost damage.  After fire and wind, if soils are dry and there is still green leaves on the canopy, irrigation after the event may be necessary.  The key is to check the soil moisture, and if dry, water.

Pruning

Do no prune until you know how much of the tree has been killed. New foliage will grow from the remaining live wood and the tree will recover better without pruning.

When new shoots are at least two or three feet long, you can remove the dead wood. This will usually be mid-summer, 6 to 8 months following the frost/fire event. At the same time, suckers should be thinned out to select the new limbs to replace those lost.

Care of young trees

Badly damaged young trees usually develop strong sucker growth which can be used to form a tree as good as a replanted tree. If these suckers are from above the bud union, you can develop a new top by thinning and training. On young trees damaged to the bud union, strong root suckers can be budded or grafted to the desired variety the following spring. If the sucker growth is weak, the tree should be removed.  Trees less than two years of age with only green tissue are usually a lost cause.

Severely damaged mature trees

The handling of severely damaged mature trees where they have been killed back to the large scaffold limbs, to the trunk, or to the ground, presents many problems. Each tree should be considered separately. Often growers can topwork badly frozen trees to a more resistant or productive variety.  The hardest thing is to figure out how to treat the range of damage to trees in a single irrigation block - some will need a regular irrigation, some less, and some none at all.  Balancing a checker board of trees is difficult.

Two Years After the Fire

avocado burned 2 years later 3

Fire Information for Tree Crop Growers

The following is a compendium of blogs for growers to help with the recent fire damage in the Ventura area:

https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=26670

https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=28711

https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=26510

https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=26353

https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=26095

https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=25899

https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=25885

https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=24639

Don't hesitate to contact me, at

805-645-1462

bafaber@ucanr.edu

IMG 2040

USDA Brings Back the Goods - Fruit

You may not have heard of USDA plant explorers David Fairchild and Palemon Howard Dorsett, but they are among those who have had the greatest impact on what we eat in the United States. Now a silent film of their 1925–26 collecting trip to Ceylon (Sri Lanka), Sumatra, and Java has been found by the National Agricultural Library (NAL).

One hundred years ago, the national cuisine was rather plain—heavy on meat, potatoes, and cheeses, and with a very limited palette of fruits and vegetables. But Fairchild, Dorsett, and other USDA plant explorers trekked across the world to find new crops and ornamental plants for the country.

Fairchild alone is credited with the introduction of more than 200,000 exotic plants and crop varieties, including avocado, flowering cherry trees, hops, horseradish, kale, nectarines, papaya, and pistachios.

Dorsett is best known for collecting germplasm that has helped to build soybeans into a $40 billion-a-year U.S. crop.

In 1925, Fairchild and Dorsett led a USDA expedition to Ceylon, Sumatra, and Western Java, during which they scoured markets, botanical gardens, farms, roadsides, and even beaches to collect seeds and plant specimens. Accompanying the explorers was Dorsett's son Jim, whose job was to document the trip photographically.

Jim Dorsett was equipped with a then state-of-the art Sept camera that could take sharp still photos, fast-action sequence photos, and movies. Fairchild was the first to acknowledge that Jim Dorsett's equipment and techniques were far superior to his own. But he was not the last, as National Geographic hired Jim Dorsett soon after he returned from the expedition.

Recently, NAL's Special Collections staff began an inventory of their 16-mm films. They discovered a poorly labeled film canister. Once they began watching, it didn't take long into the 21:06-minute silent film to realize what they had.

“It is an amazing film,” says botanist Karen Williams with the Agricultural Research Service's National Germplasm Resources Laboratory. “It offers rare insights into how people were using plants at that time. Were they using the same plants in different ways than is now common in the region? In addition, they included natural habitats in the film. Botanists may be able to make comparisons between some of the plants that are identifiable in the film and plants known to occur in the same region today—or they may find that some are rare or even extinct today,” she adds.

A collaboration between NAL and the Fairchild Tropical Botanic Gardenin Coral Gables, Florida, has begun to interpret the botanical and historical context of the film.

“A fascinating movie to watch and a real jewel in ethnobotany, particularly when you consider it was made in the early 20th century,” says Fairchild Tropical Botanic Garden adjunct faculty and Florida International University professor Javier Francisco-Ortega. “The film covers so many things: new crops, plants as avenues to teach, ethnography, plants as tools and building materials. There is one sequence where you see them collecting a certain bamboo and then a man building with it.”

You can watch a digitized version of the entire film on YouTube  Those were the days of really getting into travel.

Paula Sewell has biographies of three of the  USDA explorers - David Fairchild, Frank Meyer (Meyer Lemon) and Wilson Popenoe (Pop Enoe).  Turns out Popenoe retired to Antigua Guatemala and Tony Brown of Carpinteria went to the guru to learn more about the cherimoya and how best to nurture it here and from there the crop flourished and the whole family was involved - Johnny, Peter and Emily.

Wilson Popenoe in the field on his horse Starlight using a McClellan saddle

ARS Office of Communication

UC Riverside Happenings

UC Riverside awarded $1.5 million for sustainable agriculture initiatives

RIVERSIDE, Calif. -- The University of California, Riverside, has been awarded $1.5 million in grants from the California Department of Food and Agriculture to lead three interconnected projects aimed at transforming California's specialty crop farming. The initiatives focus on youth engagement, sustainable waste management, and advanced agricultural technologies.

“These multidisciplinary projects are designed to address complex food system challenges by integrating diverse perspectives,” said Deborah Pagliaccia, a professional researcher in the UCR Department of Microbiology and Plant Pathology and co-principal investigator of the grants. “They aim to foster a learning environment where students and stakeholders contribute to a cohesive curriculum that bridges the gap between theoretical knowledge and practical application.”

Each of the three projects has received about $498,000 in funding and will integrate education, research, and practical application to help shape a sustainable future for global food systems.

“We are also committed to equipping and informing students with the knowledge and skills necessary for careers in agriculture,” said Georgios Vidalakis, a professor of plant pathology and director of the UCR Citrus Cloning Protection Program, who is the grants' principal investigator. “We will use a holistic teaching approach to enhance academic and professional development and prepare students to continue their education or enter the job market as effective change agents.”

The first project is titled “Seeding Success: Youth Engagement and Skill Development for Sustainable and Resilient Specialty Crop Farming in California.” Led by UCR in collaboration with UC Agriculture and Natural Resources, the Growing Hope Project, John W. North High School, and San Andreas High School, the project aims to cultivate a skilled, diverse, and adaptive workforce prepared to meet emerging climate and socio-economic challenges in California's specialty crop sector. 

A key component is the development of a new course, “Sustainable Agri-Food Systems and Circular Economy,” which is designed to educate, engage, and empower high school and UCR undergraduate students to address global food security and environmental sustainability challenges. Students will participate in workshops, labs, field visits, and internships that offer them practical experience in sustainable farming technologies such as controlled environments, insect-based farming, climate-smart agriculture, and nature-based farming.

The second project is titled “Closing the Loop: Transforming Agri-Food Waste into Sustainable Carbon-Based Soil Amendments and Fertilizers.” Researchers will address climate change, improve soil health, promote sustainability, and enhance carbon sequestration practices. Specifically, they will divert waste from landfills, reduce greenhouse gas emissions, and lower reliance on synthetic fertilizers. They will also transform agri-food waste into valuable soil amendments, research the impacts of organic waste-based soil amendments on field-grown trees and greenhouse-grown vegetables, engage underserved farmers, and create internships for UCR students.

The third project is titled “Sustainable Citrus: Unlocking the Potential of Controlled Environment Agriculture for Commercial Nursery Growers.” With the goal of translating scientific discoveries into practical solutions for commercial growers, the project will enhance controlled environment agriculture technologies for citrus nursery growers. Researchers will focus on optimizing light conditions to improve plant growth and stress resilience while also enhancing the quality of disease-free plants and improving energy and cost efficiencies. Researchers will train underserved farmers and offer internships to UCR students to give them hands-on experience in advanced agri-food systems technologies.

All three projects, which begin November 1, 2024, and end June 30, 2027, will be interconnected through their use of labtofarm.org, a platform dedicated to bridging the gap between laboratory research and practical farming applications. The platform will allow researchers to disseminate their findings, engage with a broader community, and develop sustainable methodologies that are economically viable and environmentally friendly.

“LabtoFarm.org will allow us to engage undergraduate students, underserved farmers, and various stakeholders in a meaningful exchange of knowledge and innovation,” Pagliaccia said. "The platform also serves as a hub for student internships and collaborative projects, offering valuable opportunities for professional growth, hands-on experience, and direct involvement in sustainable agri-food systems practices."

According to Vidalakis, UCR is well positioned to conduct the three projects because of its location.

“We are one of very few universities conducting agricultural research that are located in urban environments,” he said. “Ours gives us access to more young minds that we can train to become business owners, entrepreneurs, and government officials. Traditionally, large urban centers have been generators of research, development, and new technologies and ideas.”

Pagliaccia, who has extensive expertise in sustainable agri-food systems, said the idea for the three projects was conceived during her service as managing director of UCR's California Agriculture and Food Enterprise, or CAFÉ.

“In CAFÉ, we worked to empower the community to make well-considered decisions toward a sustainable and economically successful future for global agri-food systems, which is also the overall goal of our three projects,” she said.     

Pagliaccia and Vidalakis will be joined in the projects by co-principal investigators Samantha Ying, Robert Jinkerson, Sohrab Bodaghi, and Arunabha Mitra at UCR; and Jonathan Kaplan at Sacramento State University.

Iqbal Pittalwala
University of California - Riverside
iqbal@ucr.edu
Office: 951-827-6050

 

 

citrus and mountains

My Frost Protection Spray Trials

The use of foliar nutrients as frost protectants has been promoted for years. Research published by Steve Lindow at UC Berkeley explained that certain naturally occurring bacteria ,such as Pseudomonas syringae and Erwinia herbicola act as nucleating agents for ice formation. The presence of these ice-nucleation-active bacteria results in the formation of ice crystals in plant tissue at temperatures several degrees higher than in their absence. When water in plant cells freezes, it expands and ruptures the cell walls, leading to cell necrosis. The bacteria can be killed or prevented from acting as nucleating agents, thus providing several degrees of frost protection.

This discovery provided a plausible explanation for the previously observed positive effects of foliar sprays on freeze tolerance. While the mechanism can be explained, there is no general agreement on which chemicals are most effective in controlling the ice-nucleating bacteria. These products need to be applied early enough to remove the ice-nucleating bacteria, but not so early that they have a chance to return.

Several specially formulated products are commercially available, but in controlled tests these have generally not given better results than copper-based fungicides or micronutrient mixtures. Certain urea-based products, antibiotics, anti-transpirants, and surfactants have also claimed to be effective.

At issue is not only these surface-dwelling bacteria, but also the age of the tree, development of the canopy, the length degree of the freeze event, the health of the tree, nutritional and irrigation status and when the event occurs. Trees that gradually go into a quiescent stage of winter, are better able to sustain cold stress than those that are hit early on before they start shutting down for winter. Trees develop a cold-hardiness. And plant growth regulators, those both internal and external, play a roll.

I have run trials where I have seen incredible effects after using a certain type of kelp. Kelp has all kinds of ingredients, and they vary depending on what part of the ocean, what species, when it is harvested and how it is processed. When trying to reproduce the effect I had initially seen with the same kelp or other sources, I was not able to get the same effect. This was in three separate trials. It's hard to reproduce the same conditions or the right time of application. The river never runs the same.

Foliar sprays are capable of influencing frost tolerance. Copper and zinc have most consistently shown a positive effect. And the most vulnerable would be small trees that are the easiest to spray. It's a relatively inexpensive treatment and depending on the mate4rial, can be used in both conventional and organic orchards.

You can read about our four-year evaluation of materials for reducing frost damage. There were some positive results, but they are also equivocal - https://ceventura.ucanr.edu/Com_Ag/Subtropical/Publications/Frost/Foliar_Sprays_for_Frost_Protection_of_Young_Citrus_and_Avocado_-_1995_/

frost damage

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