- Author: Ed Perry
For many in California, the backyard orange or grapefruit tree is almost a member of the family, and any negative change in its appearance elicits concern. One such change in appearance is leaf yellowing and drop that often occurs during the winter in citrus. Citrus leaves can remain on the tree for as long as three years depending on tree vigor, but disease, inadequate or excessive nitrogen fertility, excessive salt or born in the soil, poor irrigation practices, freezing temperatures, pest pressures and low light levels significantly reduce leaf longevity. Excessive leaf drop during the growing season is more likely to indicate a serious problem than leaf drop during the winter. Winter leaf drop normally reflects nothing more than a momentary swing in the natural balance between the natural elimination of old senescing leaves and their replacement.
Reduce winter water applications to citrus trees that have defoliated or that have a significantly thinning canopy. Trees like this require little, if any, supplemental irrigation. Even a mature tree with a full leaf canopy will require less than 10% of the water that it would require during the summer.
The best indicator of tree health for a defoliating citrus tree during the winter will be how well it produces the first flush of new growth in the spring. A decision to keep or remove a citrus tree based on tree health should not be made during the winter. Even trees that lose most of their leaves during winter are capable of replacing leaf canopies with the spring flush of growth, usually with little loss in fruit production. Trees that do not produce a vigorous flush in early spring may have a more serious problem. March is an excellent month to begin applying fertilizer to encourage new leaf growth and fruit production and to help keep an old friend of the farm or family backyard around for years to come.
Ed Perry is the emeritus Environmental Horticultural Advisor for University of California Cooperative Extension (UCCE) in Stanislaus County where he worked for over 30 years.
- Author: Pamela Kan-Rice
A new study on the costs and returns of establishing and producing lemons in Ventura County has been released by UC Cooperative Extension in Southern California and UC Agricultural Issues Center, both part of UC Agriculture and Natural Resources.
“Coastal agriculture is always in transition and as strawberries and vegetables become less profitable due to markets and labor availability, lemons have returned as a potentially profitable alternative to those crops,” saidBen Faber, UC Cooperative Extension farm advisor for Ventura County and coauthor of the study.
California lemon acreage was at roughly 47,000 acres in 2018-19, of which Ventura County accounts for 31%, according to the 2019 Ventura County Crop Report. Ventura County was growing lemons on 14,407 acres in 2019.
“The profitability of lemon production depends on the price of land,” said Etaferahu Takele, UC Cooperative Extension farm management advisor for Southern California, another coauthor of the study. “If the price of land continues in its current trend, it could be prohibitive for new entrants to make a profit and limit further expansion of lemon production in the county.”
Their cost analysis describes production operations for Eureka lemons on macrophylla rootstock, which are planted at 155 trees per acre with an expected life span of 40 years.
The study includes a detailed summary of costs and returns and a profitability analysis of gross margin, economic profit and a break-even ranging analysis table, which shows profits over a range of prices and yields.
Input and reviews were provided by Ventura County farm advisor and grower cooperators. The authors describe the assumptions used to identify current costs for lemon establishment and production, material inputs, cash and non-cash overhead.
The new study, “2020 - Sample Costs to Establish and Produce Eureka Lemons in Ventura County,” can be downloaded for free from the UC Davis Department of Agricultural and Resource Economics website at http://coststudies.ucdavis.edu and the UCCE Riverside County Farm Management website at https://ucanr.edu/sites/Farm_Management/files/338947.pdf. Sample cost of production studies for many other commodities are also available on the websites.
For additional information or an explanation of the calculations used in the studies, refer to the section of the report titled “Assumptions” or contact Takele at (951) 683-6491 Ext. 243 ettakele@ucanr.edu or Donald Stewart at the UC Agricultural Issues Center at (530) 752-4651, destewart@ucdavis.edu.
For information about production of lemons in Ventura County, contact Faber at bafaber@ucanr.edu.
- Author: Ben Faber
Now we know
A team of researchers, including two from the University of California, Riverside, has identified the genes responsible for the hallmark sour taste of many citrus fruits. Published Tuesday, Feb. 25 in Nature Communications, the research could help plant breeders develop new, sweeter varieties.
Modern citrus varieties have been bred over thousands of years to generate a broad palette of sour and sweet-tasting fruits. Analyses of their pulp reveals that a single chemical element--hydrogen--is largely responsible for the difference between sour and sweet-tasting varieties, which usually have similar sugar content. The pulp from sour fruits contains more hydrogen ions, giving it a lower pH and a tangy taste that is recognized by acid-sensitive cells in our taste buds. Conversely, pulp from sweeter varieties contains fewer hydrogen ions and tastes less acidic.
Ronald Koes and colleagues at the University of Amsterdam in the Netherlands set out to untangle how some citrus varieties wind up with more acidic juice than others, a process that until now has remained a mystery. Their interest stemmed from a previous study showing that higher acidity in purple petunia flowers resulted in more petal pigmentation.
Intrigued by the Faris variety of lemon tree, which produces branches bearing both sweet and sour fruits, and white and purple-tinged flowers, Koes' team turned to UCR plant scientists Mikeal Roose and Claire Federici. Using the university's vast Citrus Variety Collection, which preserves over 1,000 living citrus and related fruit varieties, Roose and Federici selected the Faris lemon and 20 other citrus fruits ranging from wincingly sour to sugary sweet for Koes' team to analyze.
By studying the expression of genes related to those controlling acidity in petunias, Koes' team identified two citrus genes, CitPH1 and CitPH5, that are highly expressed in sour varieties and weakly expressed in sweet-tasting varieties. The CitPH1 and CitPH5 genes encode transporter proteins that pump hydrogen ions into the vacuole, a large storage compartment inside juice cells, thus increasing their overall acidity.
Next, the team turned its attention to genes that control the levels of CitPH1 and CitPH5 in juice cells. While down-regulation of CitPH1 and CitPH5 in sweeter tasting varieties arose multiple times independently in different varieties, the researchers found that mutations in genes for a handful of transcription factors (proteins that help turn specific genes on and off) were responsible for reduced expression of CitPH1 and CitPH5, and therefore a sweeter taste.
Roose, a professor of genetics in UCR's College of Natural and Agricultural Sciences, said the findings could help breeders develop better-tasting citrus fruits. However, he said breeding varieties with severe mutations in the transcription factors such as those studied in the "acidless" citrus would be "overkill," producing sugary citrus fruits with none of their popular acidic kick. Instead, plant scientists should look to target mutations that have a less dramatic effect on the production and activity of transporter proteins.
"By understanding the mechanism acidification of fruit cells, we can now look for related genes that might reduce the expression of CitPH1 and CitPH5 just enough to engineer or select for new, sweeter varieties," Roose said.
Hyperacidification of Citrus fruits by a vacuolar
proton-pumping P-ATPase complex
Nature Communicationsvolume 10, Article number: 744 (2019)
/h1>/h1>- Author: Ben Faber
There's so much gloom about the fate of citrus in Florida and California, but in spite of that talk, world citrus production is increasing.
Global orange production for 2018/19 is forecast to expand 4.2 million tons from the previous year to 51.8 million as favorable weather leads to larger crops in Brazil and the United States. Consequently, fruit for both fresh and processing uses is expected to be greater. Fresh exports are forecast 4 percent higher to 5.1 million tons.
Brazil's production is forecast to rise 13 percent to 17.8 million tons as favorable weather is expected to result in good bloom and fruit set. Fresh orange consumption and exports are flat while oranges for processing are up 2.0 million tons to 12.8 million.
China's production is projected down slightly to 7.2 million on unfavorable weather, resulting in a smaller crop in Jiangxi province. Along with only a small increase in imports, consumption is
lower on overall reduced supplies. South Africa and Egypt are the top two suppliers, accounting for 60 percent of imports.
U.S. production is forecast to recover, jumping 41 percent to 5.0 million tons due to favorable weather. Orange production in Florida has been declining for years due to citrus greening, which has decimated groves and increased costs for crop maintenance.
However, last year, the industry also suffered from damages caused by Hurricane Irma. This year's higher forecast shows a recovery to recent-year levels. Exports, consumption, and fruit for processing are all higher with the larger crop.
Read more about the world citrus industry and get individual country reports generated by the USDA's Foreign Agricultural Service
https://agfstorage.blob.core.windows.net/misc/FP_com/2019/03/04/Florr.pdf
FAS Reports from Overseas Offices The Citrus: World Markets and Trade circular is based on reports from FAS Overseas Posts since December 2018 and on available secondary information. Individual country reports can be obtained on FAS Online at: http://gain.fas.usda.gov/Pages/Default.aspx .
- Author: Ben Faber
Harry S. Smith, was born in 1883 to a poor farming family in Nebraska. He was trained in Biological Control in the northeast U.S.A. where he worked on the biological control of gypsy moth with the USDA. Upon his appointment to Sacramento in 1913 to work on biological control issues important to California, Smith brought recognized entomological training in biological control to California for the first time.
The phrase “Biological Control” was first used by Smith in August 1919 at the meeting of Pacific Slope Branch of the American Association of Economic Entomologists at the Mission Inn in downtown Riverside.
Based on his experiences on biological control of forest and pasture pests, Smith brought caution and tempered exaggeration about biological control in California as he worked with citrus growers and other commodity groups.
In 1923, Smith and four colleagues moved from Sacramento to the University of California Riverside Campus which had evolved from the Citrus Experiment Station (est. 1915) and he formed the Division of Beneficial Insect Investigations which was a unit distinct from the Division of Entomology. Prof. Harry, as he was
affectionately known, is fondly remembered by his students as a patient and generous supervisor who encouraged research and work on applied and
practical aspects of biological control.
Smith went on to create the Department of Biological Control which offered the only graduate training in Biological Control in the world. The Department of Biological Control became the Division of Biological Control in 1969 which then merged into Department of Entomology at UC Riverside in 1988. Prof. Harry had two sons, both trained to be entomologists. Instead of pursuing biological control they went into the pesticide industry and Sam Smith died accidentally from pesticide poisoning. Prof. Harry passed away in 1957 and left UC Riverside $15,000 to develop a scholarship fund to support training and education in biological control. This fund has grown to approximately $45,000 today, but is insufficient to provide meaningful support to students wanting to be trained in biological control.
Our goal is to build the Harry S. Smith Scholarship fund to a significant level where the corpus of the fund will be able to generate enough revenue to provide substantial support to students wanting to be trained in biological control. This can only be achieved by actively soliciting donations from individuals, industries, and organizations that have benefited over the years from biological control projects that have that have been run by UC scientists, in particular entomologists at UC Riverside. If biological control is to continue to prosper in southern California we need to continue recruiting and training high quality students. To do this, we need to be able to provide substantial financial support, and the Harry S. Smith Scholarship is one way to attract excellent students to UC Riverside.
Learn more about the program and how you can push the fund over the top at:
http://biocontrol.ucr.edu/hoddle/harrysmithfund.html