California Ag Network

Category: Citrus Industry

  • US Increases Market Share of Stone Fruit Exports in Taiwan

    In 2019, U.S. peach, nectarine, and cherry exports to Taiwan increased as competitor market share declined. Taiwan’s peach and nectarine production is forecast to increase from 16,171 metric tons (MT) in 2019 to 19,000 MT in 2020 due to improved bearing. Taiwan’s robust handling of COVID-19 has led to a modest recovery in domestic consumption, which has allowed consumption to remain strong and imports to remain stable. In 2020, total Taiwan peach and nectarine imports are forecast to increase nominally to 15,000 MT and imports of cherries are forecast up at 12,000 MT.

    Read the full report from the USDA Foreign Agricultural Service HERE.

  • Removing Avocado Suckers with Glyphosate

    This is not good. You find an avocado tree with sun blotch or it is time to thin the orchard and you remove the offending tree. You know that if you don’t remove the sucker, you’ll end up with some rootstock growth that just gets in the way of the other trees. Avocado suckers can look like a valued tree until it’s time for harvest several years later, and then you are likely to find that it’s not the variety that you thought it was. Homeowners often find this problem several years after a freeze and the lemon tree that regrew from the freeze damage turns out to be the rootstock variety and produces some gnarly, seedy, juiceless fruit. Even without a frost, sometimes rootstocks which are selected for their vigor, can be more vigorous than the scion variety and will overgrow it. You then end up with whatever the rootstock fruit turns out to be.

    In some situations, it is legal and common to use a “cut stump” treatment to kill stumps and prevent resprouting. In these cases, glyphosate or triclopyr is sprayed, drizzled, or painted onto a freshly cut stump. Relatively high concentrations of the herbicide are applied to the cambium, which is the living tissue just under the bark. Cut stump treatments work well in many situations, including citrus orchards. This type of cut and spray treatment is commonly done to remove undesirable plants, like arundo and weedy tree species. However, in some trees, like avocado and many forest species, there can be root grafting, which are tree-to-tree root connections.

    Due to root grafting in a mature avocado orchard, it really can be one giant root system, one tree connected to all the other trees. And if a systemic herbicide is injected in one tree, the surrounding trees can be affected – they might get enough herbicide through the root graft to be injured or even killed along with the target tree. This technique has been used in Florida to remove Laurel Wilt Disease infected avocado trees which can rapidly infect surrounding trees with the killer fungus. This is a helpful technique, because it removes any doubt that all infected trees have been killed to prevent the spread to healthy trees in the orchard.

    In a healthy orchard in California, this is not a really good way to remove avocado stump sprouts. Every year reports come in of glyphosate killing good trees that surround a removed tree. Figure 3 is a recent case where the stump (circled in blue) was scored and painted with glyphosate. Within two weeks the surrounding tree were also killed. The systemic material was translocated from the cut surface by way of root grafts to the neighboring trees. And those trees are now dead, too.

    The stump (circled in blue) was scored and painted with glyphosate.

    So what to do? One thing done by those with a front-end loader or a backhoe, is to pull the stump and have an end to the sucker problem. It also reduces the possibility of chronic armillaria fungus persisting to infect trees. The problem is that it leaves a big hole to deal with which can open up a slope to erosion. If on a slope, it requires a decent sized tractor that can safely be operated on the slope without tearing up everything, including the irrigation system. And in the end, it’s expensive.

    The other approach is to just cut the tree down as low as possible without damaging the chain saw. Then as the irrigator makes inspections, just physically knock off the suckers as they come up. If walking the irrigation lines, it’s not a problem. Covering the stump and immediate area with a physical barrier such as thick, black plastic sheet (greater than 5 ml), can reduce the number of suckers. To speed degradation of the stump, the top of the cut can be scored and a salt such as urea or magnesium sulfate (both at 10 pounds per stump) can be applied. At this rate, rather than fertilize the stump, under moist conditions, this treatment facilitates the activity of wood-decaying microorganisms; it can also damage or reduce the regrowth of the suckers.

    There are also a range of registered contact herbicides that can be used to burn out the suckers. Materials, such as Scythe®, Axxe® and Suppress® are all registered for avocado sucker control. There are others. These contact herbicide work best on small tender suckers so don’t let the suckers grow more than a foot or so. For best control of suckers, apply them at the highest allowable rate with an approved adjuvant at a spray-to-wet rate. Because these products are not systemic, you’ll likely need repeat applications, as new fresh buds break and new suckers erupt.

    Using a contact spray means the grower would still need to be out in the orchard controlling the suckers. The grower still needs to be out in the orchard checking the irrigation lines. Why spray the suckers when they can just be broken off?

    Although systemic herbicide can be used effectively to control suckers or stump sprouts in some tree crops or situations where root grafting does not occur, this is not a recommended practice for avocado because of the risk of damage to nearby trees. — By Ben Faber & Brad Hanson, UC Cooperative Extension

  • California Citrus Acreage Report: Increase in Lemons & Mandarins

    The Pacific Regional Office of the USDA’s National Agricultural Statistics Service (NASS) conducts an acreage survey of California citrus growers as funding is available. The purpose of this survey is to provide bi-annual citrus acreage, which includes information on new plantings and removals. It is the continuation of a long series of industry-funded Citrus Acreage surveys.

    Users are cautioned that this report consists of two parts:

    – Table 1 shows estimated statewide bearing acreage for the 2017-18, 2018-19, and 2019-20 seasons.

    -Tables 2, 3, and 4 show detailed acreage data by type, variety, and year planted — as voluntarily reported by citrus growers and maintained in NASS’ database.

    With perfect information, the estimated statewide bearing acreage and the detailed acreage data would be the same. Generally, this will not be the case for the following reasons:

    -A voluntary survey of approximately 5,400 citrus growers is unlikely to ever attain 100 percent completeness.

    -It is difficult for USDA/NASS to detect growers who are planting citrus for the first time. 

    PROCEDURES

    The major source of the citrus detailed acreage data was a questionnaire mailed to all citrus growers currently on NASS’ database. The mailing was made in January 2020 to approximately 5,400 citrus growers. The questionnaire contained previously reported crop, variety, and acreage information preprinted. Producers were asked to update the information with new plantings, removals, and any other corrections; and new growers were mailed a blank questionnaire. Growers were given about eight weeks to respond by mail. A telephone follow-up was then undertaken. Field personnel were unable to personally visit large growers who did not respond by mail because of social distancing requirements that have been in effect since March 2020.

    To arrive at the estimated statewide bearing acreage, the NASS citrus acreage database was compared with pesticide application data maintained by County Agricultural Commissioners and the Department of Pesticide Regulation.

    ACKNOWLEDGMENTS

    Thank you to the many orchard operators, owners, and management firms that provided their acreage information. Funding for the survey was provided by the California Citrus industry.

  • Managing Heat In California Avocado Groves

    California Avocado Commission — According to a new report released by the California Department of Food and Agriculture (CDFA) and the Climate Science Alliance, Southern California agricultural regions will face more climate extremes — notably higher daily maximum temperatures and more frequent and intense heat events — in the coming decades. As Dr. Ben Faber notes in a recent blog post, although avocado groves have been successful in California, the trees are “poorly adapted to high temperatures and low humidity.” Therefore, avocado growers throughout the state should be aware of the impacts of heat on their trees.

    Avocado trees cool themselves by moving water through the roots and out their leaves through leaf pores known as stomates. As the water evaporates from the leaves, it helps maintain leaf temperature as well as prevent the trunk and branches from overheating. During a heat wave, an avocado tree tends to close its stomates to prevent excess water loss, which results in the leaf temperature increasing. In extreme circumstances, the leaves and stems can overheat and literally cook.

    California avocado varieties have different sensitivities to heat. While ‘Pinkerton’, ‘Lamb Hass’ and ‘Reed’ varieties are less susceptible to heat, ‘Hass’ and ‘Fuerte’ are most sensitive; and ‘Sir-Prize’ and ‘Sharwil’ tend to be somewhere in the middle.

    Protection Measures

    The timing of heat waves in California tends to coincide with peak season — when trees are producing their summer flush. When the temperatures is 100˚F or above, the trees tend to drop their fruit and flowers, thus excessive heat can impact the following year’s bloom.

    Well-watered trees will better tolerate the stresses imposed by a heat wave. Thus, growers should irrigate their trees in advance of a heat wave to ensure they are fully hydrated. Apply an additional 50% of the budgeted amount of water. If the heat wave lasts for several days, be certain to provide daily pulses of irrigation.

    Because avocado roots grow near the surface of the soil, mulch also helps trees manage heat by keeping the soil (and roots) cool.

    Cover crops also can aid in keeping groves cool. The cover crop can prevent water runoff, improve water retention in the soil, lower the air temperature in the grove and keep the soil cool.  In addition, cover crops will help improve soil structure, suppress weeds, increase soil organic matter and provide a home to beneficial pollinators and insects.

    Harvest During a Heat Wave

    Best practice is to make every attempt to wait and harvest fruit when the temperature is below 90˚F. No fruit should be harvested when the temperature is above 95˚F.

    When fruit is harvested during warmer temperatures, place the field bins in the shade to avoid exposing the harvested fruit to sunburn.  If fruit is left exposed to direct sunlight, the sunburn will only show up after it has been packed. Bins should be covered with bin covers or light-colored tarps. And bins should be sent to the packinghouse promptly to avoid decreased fruit quality caused by water loss.

    Heat Damage

    If you see significant leaf drop in your groves due to excessive heat, the following actions are recommended:

    • As soon as possible, whitewash branches exposed to the sun with special attention paid to branches on the west and south sides of the tree.
    • Trees that lose a significant portion of leaves cannot efficiently move water, therefore restrict irrigation amounts to ensure you avoid creating wet, soggy conditions that can lead to root rot. It’s best to irrigate less frequently and with smaller amounts of water.
    • Do not prune your trees — leave hanging leaves in place to protect the tree from sunburn. Once new tree growth has occurred (in the next 3 – 6 months), pruning can take place on living wood.
    • Adjust fertilization as you would with a frost-damaged tree: reducing the amount of fertilizer until the tree is re-established. If you see signs of a particular nutrient deficiency, adjust fertilization accordingly.

    For more information about managing heat in avocado groves, growers can view the following articles on the California avocado growers’ website:

  • CA Navel Orange Forecast Down 5%

    The initial 2020-21 Navel orange forecast is 84.0 million cartons, down 5 percent from the previous year. Of the total Navel orange forecast, 81.0 million cartons are estimated to be in the Central Valley. Cara Cara variety Navel orange production in the Central Valley is forecast at 7.0 million cartons. These forecasts are based on the results of the 2020-21 Navel Orange Objective Measurement (O.M.) Survey, which was conducted from June 15 to September 1, 2020. Estimated fruit set per tree, fruit diameter, trees per acre, bearing acreage, and oranges per box were used in the statistical models estimating production.

    This forecast includes production of conventional, organic, and specialty Navel oranges (including Cara Cara and Blood orange varieties).

    Survey data indicated a fruit set per tree of 319, unchanged from the previous year but b e l o w the five-year average of 363. The average September 1 diameter was 2.198 inches, below the five-year average of 2.218 inches. The Cara Cara orange set was 251 with a diameter of 2.232 inches.

    SURVEY SAMPLE

    A sample of 785 Navel orange groves was randomly selected proportional to county and variety bearing acreage, and 733 of the groves were utilized in this survey. Once a grove was randomly chosen and grower permission was granted, two trees were randomly selected. The Navel orange sample included conventional, organic, Cara Cara, and Blood orange groves.

    For each randomly selected tree, the trunk was measured along with all connected branches. A random number table was then used to select a branch, and then all connected branches from the randomly-selected branch were measured.

    This process was repeated until a branch was reached with no significant limbs beyond t h i s p o i n t . This randomly-selected branch, called the terminal branch, was then closely inspected to count all fruit connected to this branch, as well as all of the fruit along the path from the trunk to the terminal branch. Since each selected path has a probability of selection associated with t h e p a t h , a probability-based method was then applied to estimate a fruit count for the entire tree.

    In the last week of the survey period, fruit diameter measurements were made on the right quadrant of four trees surrounding the two trees of every third grove. These measurements were used to estimate an average fruit diameter per tree. Of the 733 utilized groves, 11 were in Madera County, 125 were in Fresno County, 436 were in Tulare County, and 161 were in Kern County.

    SURVEY HISTORY

    A Navel Orange Objective Measurement Survey has been conducted in the Central Valley every year since the 1984-85 crop year, except for the 1991-92 season due to a lack of funding. The data from the first two years were used for research purposes in developing crop-estimating models. The Cara Cara forecast was undertaken at the request of the California Citrus Advisory Committee. 

     

  • CA Citrus Mutual Commends Actions Regarding Seasonal & Perishable Products

    California Citrus Mutual commends the Office of the U.S. Trade Representative (USTR), U.S. Department of Agriculture (USDA), and U.S. Department of Commerce (DOC) for the actions they recently announced to address the injury caused by increased imports of seasonal and perishable products. Low-priced imports have previously caused a substantial market disruption for the California citrus industry during its marketing season. We are encouraged by both the Administration’s plan and its determination to bring relief to fruit and vegetable growers who are suffering from similar import issues.

    The trade remedy steps announced include the self-initiation of Section 201 global safeguard action on certain imports, USTR’s coordination with specific sectors to monitor and investigate imports under the Section 201 provisions covering perishable agricultural products and citrus products, DOC’s coordination with effected sectors on possible self-initiated antidumping and countervailing duty actions, and the Administration’s indication that still other actions and investigations may be taken. These steps are essential safeguarding and supporting all U.S. fruit and vegetable growers harmed by this problem.

    In 2017, low-priced citrus imports from the Southern Hemisphere increased 40% over the prior year’s shipments, causing significant price declines and harm to California growers. Consistent with last week’s announcement, California Citrus Mutual will closely monitor imports in the coming California season and continue to coordinate with the U.S. Government regarding any import surges, unfair import practices, and injury to our citrus growers.

    About California Citrus Mutual (CCM)

    CCM is a voluntary, non-profit trade association representing CA citrus growers on the economic, regulatory, and political issues that impact them most.

  • CA Prune Board Sees High-Quality Fruit in Short Crop Year

    The California Prune harvest wrapped up on schedule this year and growers have worked through the challenges of wildfires and market disruptions caused by the pandemic to harvest premium quality fruit consisting of an optimum range of sizes,setting up excellent opportunities to market the sweet, larger prunes for which California is famous. With early industry projections of a short crop, growers and handlers can now estimate production of 45,000 metric tons (50,000 short tons) of California Prunes, a decrease of 37% from the previous year.  Combined with the carry-in from 2019, handlers should have sufficient supply for the new selling season.

    As markets globally adjust to a “new normal” the California Prune industry remains focused on maintaining balance of supply and demand and reliably delivering the premium fruit that the world expects. Prune growers in California play an essential role in producing a premium product that offers health benefits, great taste, versatility, and shelf stability, all vital to what consumers desire in the current environment.

    Data reported to growers and handlers at the recent conclusion of the 2019 crop year (July 31, 2020) underscored consumer desire for California’s best-in-class prunes, as shipments to export markets jumped 17% and domestic shipments improved by 12%, as compared to the previous year.

    “While the pandemic has fueled consumers’ focus on healthy foods, the California Prune industry regularly promotes the nutritional profile and invests in nutrition research that elevates the health benefits of prunes,” said Donn Zea, Executive Director of the California Prune Board. “We are grateful that so many consumers have chosen California Prunes during this time. We plan on doing everything we can to earn and keep their trust.”

    California is the largest producer of prunes, producing about 40 percent of the world’s supply, bringing quality prunes to market from 40,000 acres concentrated in the Sacramento and San Joaquin Valleys.

    ABOUT THE CALIFORNIA PRUNE BOARD

    Created in 1952, The California Prune Board aims to amplify the premium positioning and top-of-mind awareness of California Prunes through advertising, public relations, promotion, nutrition research, production research, and issues management. The California Prune Board represents approximately 800 prune growers and 28 prune, juice, and ingredient handlers under the authority of the California Secretary of Food and Agriculture.

  • California Avocado Commission Virtual Field Day, Sept. 17

    On September 17th from 3:30pm – 5:00pm the California Avocado Commission will host a virtual field day concerning Avocado Branch Canker disease that will consist of two 30-minute presentations by Dr. Themis Michailides, University of California Kearney Agricultural Center and Dr. Liz Dann, University of Queensland, followed by a question-and-answer session. Registration for the virtual event is now open.

    Dr. Themis Michailides, Professor of Plant Pathology, is one of the world’s leading experts on this group of fungi. He has been working on a CAC-funded project since October 2018 to determine exactly what pathogens cause avocado brank canker in California, the extent of their presence in California avocado groves and how they can be managed. He will present his research results to date and discuss why he believes this group of pathogens has become problematic in recent years.

    Dr. Liz Dann is a Principal Research Fellow with the Queensland Alliance for Agriculture and Food Innovation at the University of Queensland, Australia. She has worked extensively on avocado diseases in Australia and has recently started studying the role of the Botryoshpaeriaceae in flower blight of avocados in Australia. She will share her knowledge of these pathogens with growers and the impacts they have on avocado production in Australia.

    Date: September 17, 2020
    Time: 3:30pm – 5:00pm
    Location: Online Webinar

  • New Targets for Huanglongbing Treatments

    Scientists are closer to gaining the upper hand on a disease that has wiped out citrus orchards across the globe. New models of the bacterium linked to the disease reveal control methods that were previously unavailable.

    Metabolic models of organisms are like road maps of cities. “They show you all the biological processes, and how they work together,” said UC Riverside microbiology professor James Borneman. “They also show you which molecular pathways, if blocked, will kill the organism.” 

    Simplified metabolic model and its striking similarity to a road map. (Metallo&Vander Heiden)

    In this case, researchers created the first models of the bacterium associated with Huanglongbing or HLB, also known as citrus greening disease. The team’s work is described in a new paper published in Nature’s npj Systems Biology and Applications.

    The research team made models for six different strains of the bacterium known as CLas and doing so enabled them to identify as many as 94 enzymes essential for the bacterium’s survival. These enzymes can now be considered targets for the creation of new antibacterial treatments.

    In addition, the team identified metabolites required for the bacteria to grow.

    “Just like when humans break down the food they eat into small components called metabolites, which feed our cells, bacterial cells also require metabolites for their growth,” Borneman said.

    Knowing the metabolites needed for CLas’ growth could enable scientists to cultivate it in a laboratory setting. It is not currently possible to grow CLas on its own, hindering scientists’ ability to study it and ultimately to manage it.

    This research project involved a collaboration between UC Riverside, UC San Diego, Texas A&M University, and the U.S. Department of Agriculture. In addition to Borneman, members of the modeling team included UCR plant pathologist Georgios Vidalakis and UCSD systems biologist Karsten Zengler.

    UC Riverside is at the forefront of efforts to combat Huanglongbing. Other important areas of research include antibacterial development and delivery, immune system fortification in citrus, engineering resistant citrus via a detailed understanding of host-microbe interactions, breeding resistant citrus, and insect management, among others.

    Because microbes tend to mutate and acquire resistance mechanisms in response to drugs and other efforts to thwart them, Borneman cautions that any one solution to the problem may be short-lived.

    Transmission electron microscope image of CLas bacterium. (J.M. Bové/INRA)

    “Microbes almost always adapt to control measures, perpetuating the ‘arms race’ between pathogens and hosts,” Borneman said. “There won’t be one thing that will fix this disease. We likely will need to address all three components associated with the disease — the bacterium, the insect that transmits it, and the citrus plants — to find a long-lasting solution.”

    To that end, the research team is constructing metabolic models of citrus and the insect, the Asian citrus psyllid.

    “We expect that this multiorganism modeling endeavor will provide new insights into the mechanisms underlying this disease, which will lead to effective and sustainable Huanglongbing management strategies,” Borneman said. — By Jules Bernstein, UC Riverside

  • Barking Up the Right Tree: Canines Detect HLB

    In September 2019, huanglongbing—also known as HLB or citrus greening—was detected in residential citrus trees located in Ventura County, in southern California (and just recently, the first HLB carrying Asian Citrus Psyllid was detected in a commercial CA citrus grove).

    During an orchard review in California, expert detector dog, Szaboles alerts his trainer by sitting next to a citrus tree infected with Huanglongbing (HLB).

    The disease, which has no known cure, is caused by a bacterium that devastates citrus plants and is transmitted by psyllids (small plant-eating insects resembling lice) that carry the bacteria from tree to tree or by the grafting of infected plant material. Common symptoms of infection include blotchy mottling of entire leaves, premature defoliation of the tree, and fruits that are usually small, with green peel at the bottom and a bitter taste. Unfortunately, these visible signs of HLB do not manifest until months or even years after the initial infection. By then, it is too late for citrus growers to save their crop from a mass infestation.

    However, the Farm Bureau of Ventura County found a rather unconventional way around this problem.

    To contain the infected trees and prevent a citrus epidemic, the Farm Bureau decided to hire a team of detector dogs specially trained to find HLB bacteria. The dogs are a result of a unique program funded by USDA and run by Agricultural Research Service (ARS) Research Leader and Plant Pathologist Timothy Gottwald (now retired) at the U.S. Horticultural Research Laboratoryin Fort Pierce, FL.

    First, the clever canines patrolled the perimeter because the edges of a grove are where the disease would first accumulate. Then, they trotted through the grove of trees to ultimately identify over 200 infected trees from a grove of 3,500.

    According to Gottwald’s research, the canine-detection method has an accuracy rate of 99 percent. While humans need several minutes to visually examine each tree and collect samples for laboratory testing (which requires considerable lab time and supplies), the dogs can travel through groves of trees in mere minutes, sensing HLB-infected trees by smell faster and far more easily. The time saved in finding the disease earlier gives citrus growers the opportunity to remove and destroy or quarantine HLB-infected trees, controlling what could’ve been a severe outbreak and loss of crop.
     

    However, there are still some considerations to keep in mind when deploying the canines as an early detection technology. Each dog team can only work 30 minutes at a time before they must rest, and a new team takes over. Teams can work for about 6 hours a day. In addition, much like any lab equipment, dogs are periodically calibrated to the HLB “scent signature” to remain finely honed optimized detectors.

    Still, the dogs are more sensitive and accurate than any other available technology in the field. The employment of detector dogs is still a voluntary program, which means fruit growers and farmers have the choice to either use dogs to find HLB early or continue using a USDA-approved DNA test called polymerase chain reaction (PCR).

    “While PCR is an effective way to detect infections, it isn’t efficient,” Gottwald explained. “It’s difficult to pinpoint incomplete infections—or infections that are only on one part of a plant (for example, a single leaf out of an entire tree with possibly thousands of leaves)—using PCR because it requires numerous samples from all over the suspect specimen.”

    “On the other hand,” Gottwald continued, “detector dogs identify pathogens ‘holistically,’ easily locating minute infections regardless of what small part of the tree they are infecting.” With this increased scope and accuracy rate, Gottwald and his colleagues believe that the canines’ abilities will revolutionize how growers protect their crops.

    “These specially trained canines may also be used to detect diseases and infections in other fruits and vegetables, such as grapes, peaches, plums, and tomatoes,” he said. “Our research has shown that they can sense pathogens like plum pox virus or squash vein yellowing virus, which both can cause severe economic losses to agriculture industries.”

    The canine-detection method was validated in blind tests by USDA ARS in collaboration with the California Department of Food and Agriculture, with results published in 2020.— By Georgia Jiang, USDA-ARS