- Author: Pamela Kan-Rice
California's $86 million date industry produces more than half of the nation's dates. Most of the fruit is grown in the arid Coachella Valley. Despite efforts by growers to conserve water, data was lacking on date palms' actual water use to refine the best irrigation management for the crop until a recent research project led by Ali Montazar, UC Cooperative Extension irrigation and water management advisor for Imperial and Riverside counties.
“California dates are grown in the hottest and most arid climate in North America and require substantial amounts of water in order to bring a successful crop to fruition,” Albert Keck, Coachella Valley date grower and chairman of the California Date Commission, wrote in a letter of support for this project. “In addition, there is scant modern research specifically and technically focused on growing dates in North America.”
Montazar said there is a lack of irrigation management information on date palms worldwide.
“The information developed in this study is expected to have a worldwide impact,” he said.
To determine the evapotranspiration rate and crop coefficients for California date palms, Montazar teamed up with scientists at UC Davis, California Department of Water Resources, USDA Agricultural Research Service, and USDA Salinity Laboratory.
The experiment was carried out in six date orchards in the Coachella and Imperial valleys. The sites represent various soil types and conditions, irrigation management practices, canopy characteristics, and the most common date cultivars in the region.
“The findings of the project indicate that there is considerable variability in date palm consumptive water use, both spatially and temporally,” Montazar said. In other words, the amount of water the trees use varies considerably depending on each site's growing conditions.
He estimated the water needs for date palms planted in different soil types in the low desert region.
“Growers will be able to use the science-based information and tools developed by this project to determine their date palm water needs and optimize the efficiency of water and fertilizer use in their groves,” Montazar said.
The peer-reviewed article “Determination of Actual Evapotranspiration and Crop Coefficients of California Date Palms Using the Residual of Energy Balance Approach” is published in the journal MDPI Water at https://www.mdpi.com/2073-4441/12/8/2253.
“With a large quantity of new date plantings in the region, coupled with increasingly limited water resources in the Colorado River Basin Watershed, the knowledge anticipated to be developed by this research project has the potential to yield large dividends through not only improved water use efficiency, but also best management practices and crop quality,” said Keck of the California Date Commission.
Although the research focused on Coachella Valley dates, Montazar said the results are likely to be useful to growers who have orchards with similar varieties, irrigation practices, and canopy and soil features in other locations.
Montazar's co-authors are Robert Krueger of the USDA-ARS National Clonal Germplasm Repository for Citrus and Dates; Dennis Corwin of USDA-ARS U.S. Salinity Laboratory; Alireza Pourreza UC Cooperative Extension specialist based at UC Davis Department of Biological and Agricultural Engineering; Cayle Little of California Department of Water Resources; Sonia Rios, UC Cooperative Extension advisor in Riverside County; and Richard L. Snyder UC Cooperative Extension specialist emeritus in the UC Davis Department of Land, Air and Water Resources.
The date palm irrigation project was funded by the CDFA Specialty Crop Block Grant Program.
Subtropics Snapshot: The Mexican Date Industry
Noé Ortiz-Uribe1, Ricardo Salomón-Torres1, Robert Krueger2
1Universidad Estatal de Sonora; 2USDA-ARS, Riverside, CA
The crop practices used in commercial date production in Mexico are mostly the same as those used in the United States, since the main growing areas in the U.S. are close to the San Luis and Mexicali Valleys and have similar climates and soils. Some companies have plantations in both countries.
Propagation is mainly by offshoots. The main cultivar, ‘Medjool', produces many offshoots. Propagation from tissue culture is uncommon at this time, although recently there have been some plantings of tissue culture-derived palms from the U.S. and Qatar. These have not yet been field tested for performance compared to offshoot plantings.
Fertilization is provided mainly for N-P-K. In sandy soils, fertilizer is delivered via irrigation systems, and amendments for improving soil water retention are widely used. Organic production areas are small, but slowly increasing. Various farms are being certified since the market of this category of products gives better prices for the organically grown dates. Plantation practices differ based on the irrigation technique. Limited water supply is forcing irrigation to turn to pressurized systems; however, flood irrigation is the main method of water delivery. Flood-irrigated fields are leveled with laser equipment. In sandy desert areas, where flood irrigation is impractical, no leveling is required, and the use of drip irrigation with pressure-compensated drippers allows small slopes and dunes in the production field. In Baja California Sur, irrigation in modern commercial plantations is delivered by dripping systems, whereas in Coahuila, only the flooding technique is used.
The process of pollination in commercial plantations is carried out artificially, while in the oases it is performed naturally by the wind. Pollination takes place once the inflorescence is open by late February or early March. For ‘Medjool', thinning of the bunch follows pollination. Some 15 to 20 flowering strands are cut from the center of the inflorescence in April and in May fruits are removed so that there is a separation of 1 inch between remaining ones, leaving 12 – 18 fruits per strand. This practice improves fruit quality and reduces alternate bearing. A concurrent activity to the thinning process consists of the tying of the bunch to the closest leaf in a position for easy access during the following activities. This supports the bunch and reduces the number of broken fruit stalks. Sacs of mesh fabric are placed covering the fruit raceme to avoid damage from birds and insects. This activity is carried out when the fruits turn to a yellow color at the khalal stage in July to August.
Pest presence on date palms in Mexico is not significant, but there are various potential threats. Insect pests, such as various species of nitidulid beetles, have been detected infesting ‘Medjool' dates in the Mexicali valley, and red mites can cause production losses. No research has yet been done to characterize the incidence of these pests in the region. The South American palm weevil, Rhynchophorus palmarum, has been detected in cities close to the production areas; therefore, a program for monitoring its potential presence is needed.
Date palm diseases in commercial production areas are not reported yet, but some plantations in both the San Luis Rio Colorado and Mexicali regions show a few palms with symptoms similar to those of Fusarium. Since this disease can be devastating to date palms, these palms need to be closely monitored. Additional information regarding potential disease problems needs to be developed for the Mexican date-producing areas.
Vertebrate pests of date palms include squirrels and gophers. A potential vertebrate pest not found in the U.S. is the monk parakeet (Myiopsitta monachus), which makes its nest on the palms and feeds on the dates. The monk parakeet has been observed in garden palms and other plants in areas near date production in both Sonora and Baja California.
Harvest of ‘Medjool' starts in August and finishes by October. Dates are harvested from the ground or by climbing into the crown with young, short trees. Harvest of taller trees uses forklifts fitted with circular platforms that are used to elevate the crews to crown. Date fruit are harvested into circular trays consisting of fishing net over a metal form, and then lowered to the ground and placed into 2-inch deep plastic trays.
The date growing industry has the potential to contribute to the economic development of the northwest of Mexico, since there are not many other regions in Mexico that can grow high quality dates. Date growers are improving date cultural practices, and it is very possible that yields increase from the current average of 7.9 ton/ha to 10 ton/ha in the next 5 years. The main obstacle for this industry is commercialization and export. Currently, there is only one integrated company that exports the packaged fruit to other countries. Training and financing are required so that small and medium producers are better organized and form co-ops for packing and marketing of their products. In order to stimulate internal consumption, it is necessary to widely disseminate the health benefits generated by the consumption of dates. It is necessary to carry out more research on date palms in order to improve the current methods of cultivation, to be prepared for possible future pests, work with practices to optimize the use of water, and develop new products derived from the date. Likewise, research to take advantage of date palm agricultural residues, such as the extraction of oil from the seed, or use as biofuel or livestock feed is needed.
Note: This article was adapted from a longer, refereed paper. Ortiz-Uribe N, Salomón-Torres R, Krueger R (2019) Date palm status and perspective in Mexico. Agriculture 9, 46. doi:10.3390/agriculture9030046
Read more at: http://ceventura.ucanr.edu/Com_Ag/Subtropical/
- Author: Aliasghar Montazar
The dates are among the world's oldest cultivated fruits, widespread throughout North Africa, the Middle East and Southern Asia. Over the last century, distribution has extended to the United States, South Africa, India and Australia. In general, the geographical distribution of commercial date production is limited to areas that can be described as arid and semi-arid and where there is abundant water supply. The best date palm growing regions are characterized by long, hot, dry summers with minimal summer/fall rainfall. In other words, long, hot and arid growing season is required for date palm growth and to develop, mature and ripen fruits. Early maturing varieties such as Mejhool and Deglet Noor in the California low desert, require about 6,500 degree-days of heat units from flowering to fruit ripening.
The low desert region of California is the major production area of date palm in the United States with an area of nearly 10,000 acres (2017 Riverside County Agricultural Production Report and most recent Crop Acreage Report of Imperial Irrigation District). The Coachella Valley date orchards represent about 85% the total date palm acreage in California and the remaining 15% is in the Imperial Valley. The California date industry is booming, and production is expected to continue to increase as many new date palms are planted in recent years and/or are under planting.
Figure 2. Mature date palm irrigated by flood system in Thermal (left), and date palm equipped with drip irrigation in Coachella. |
Despite date palm's regional and international importance, and its dependence on irrigation or a shallow water table for survival, relatively little research has been conducted on the water relations and irrigation needs of date palm worldwide. The lack of accurate crop water use information, along with the viability of micro irrigation, are the largest uncertainties facing date palm growers in the California Low Desert. Although date palm growers have started to adopt micro irrigation, in many instances, irrigation is based upon data developed decades ago in flood irrigated orchards. Both micro/drip and flood (border) irrigation are common practices in the region, even though growers who have developed micro irrigation systems in their groves prefer to irrigate their palms through an integrated micro-flood irrigation over the season.
Utilizing drip irrigation, along with more accurate estimates of crop water use and irrigation scheduling in date orchards, may have a significant impact on water quality issues in the Salton Sea and on soil water availability, potentially increasing the economic sustainability of date production. Development of this information will enable growers to more efficiently utilize water and nutrients and to achieve full economic gains from their orchards.
The good news is that we received a grant from CDFA 2018 Specialty Crops Block Grant Program to address date palms' irrigation management related issues. The main objective of this project is to develop and disseminate information and user-friendly tools for best irrigation management practices in California date palm. A group of scientists from UC Agriculture and Natural Resources' UC Cooperative Extension, UC Davis, USDA-Agricultural Research Service, USDA-Salinity Lab, and the California Department of Water Resources are collaborating with this project.
Figure 3. One of the monitoring towers established in a commercial date palm in Thermal (left picture taken by drone), and a close view of the tower (right picture). |
To conduct the measurements, we established six monitoring towers in six commercial date palms in the Coachella Valley (Thermal, Indio/Coachella) and Imperial Valley (Westmorland and Winterhaven). Different aspects were considered to select the experimental sites, including soil type, orchard canopy feature, irrigation practice, salt affected, and non-salt affected orchards, and date variety. Since April 2019, we started comprehensive data collection using combined cutting-edge ground- and remote-sensing technologies. In each monitoring station, thirty different sensors were installed above tree canopies and in the soil to measure various parameters, including actual crop water use (evapotranspiration), weather data, canopy temperature, soil moisture in the crop root zone, and canopy greenness. The data collection will continue over a two-year period along with several drone fly-overs and soil salinity surveys. The preliminary results of this ongoing project will be published in the next few months.
/table>/table>- Author: Sean Nealon
Representatives from the date and ornamental palm industries, arborists and pest managers, parks and recreation officials, and home owners are uniting behind a University of California, Riverside initiative to slow the spread of the South American palm weevil, a palm tree-killing insect that has established in San Diego County.
“Everyone recognizes the threat and agrees it is significant,” said Mark Hoddle, UC Cooperative Extension specialist in biological control based at UC Riverside.
However, Hoddle said, action is hampered significantly by a lack of financial support at the state and federal level for research to answer questions about the distribution of the weevil in Southern California, how far it can fly from infestation zones, control options, and the most efficient and sensitive ways to monitor and trap it.
Hoddle recently helped organize a symposium just outside San Diego on the South American palm weevil. Recent detection in California of the weevil, which has traditionally been found in South and Central America, the Caribbean and Mexico, has scientists, farmers and nursery industry officials worried because it threatens California's $70 million ornamental palm industry and $68 million commercial date industry.
“My personal feeling is we might be on the verge of a crisis now,” Hoddle said. “The big problem is we don't know how far the weevil has spread. We really need help from the public in tracking its spread.”
The South American palm weevil (Rhynchophorus palmarum) is not to be confused with the palm weevil Rhynchophorus vulneratus, which originated from Indonesia and was incorrectly identified as the red palm weevil, Rhynchophorus ferrugineus, when it was found killing palm trees in Laguna Beach in 2010. R. vulneratus was declared eradicated from California on Jan. 20, 2015.
Feeding by larvae of the South American palm weevil damage the growing area of the crown of palm trees. The tree is then unable to produce new fronds, and within months it dies. Canary Islands date palms are particularly vulnerable and it is likely date palms will be attacked too. California also has a native palm species (Washingtonia filifera), which grows in desert oases and may be vulnerable to attack.
Detection of the South American palm weevil was officially confirmed May 9, 2011. Seven additional detections were made in July and August 2011. These initial detections by the USDA were in San Ysidro in San Diego County, about two miles from the Mexican border. It is likely that the weevils flew from Tijuana, Mexico, where infestations and dead palms had been detected in December 2010.
As a result of those detections, weevil traps were set up throughout California, Arizona and Texas with financial support from the USDA. A total of 111 South American palm weevils were captured in California; 109 in San Diego County and two in Imperial County. They were also found in Alamo, Texas, and Yuma, Ariz.
The traps were monitored from 2011 to 2013. Then, monitoring stopped when federal funding for the program expired.
Since monitoring stopped, it appears the problem has worsened, said Hoddle, who is also director of UC Riverside's Center for Invasive Species Research. In May 2016 he did a casual eight-hour driving survey in Tijuana, Mexico and found about 125 dead Canary Islands date palms that had been killed by the South American palm weevil.
In August, 2016, Hoddle placed 10 weevil traps at Sweetwater Regional County Park, about 15 miles east of San Diego. Since then, he has been catching about five to seven weevils per trap per month. In the coming months, he plans to start monitoring the heath of the palm trees in Sweetwater Regional Park using a drone.
Hoddle considers the South American palm weevil situation more dire than what he encountered with Rhynchophorus vulneratus because he fears the South American palm weevil has spread further and it spreads the red ring nematode (Bursaphelenchus cocophilus), which also kills palm trees.
Red ring nematodes, which have not yet been detected in California, can enter palm trees through the damage South American palm weevils do to the trees. The nematodes can also enter the bodies of the weevils when they are larvae. Then, the larvae turn into adult weevils which are strong flyers and they can then spread the nematode to other palms when the feed or lay eggs on them.
- Author: Sonia Rios
Control of weeds has always been a major economic cost in subtropical fruit production because of favorable climate that allows for weed germination and year-round growth. The use of chemical weed control has increased dramatically due to labor costs, equipment costs, product costs and availability, the shift to more narrowly spaced tree rows, and installation of low volume irrigation systems that prohibit the operation of mowing or tillage equipment under the tree canopy area (Futch 2001).
However finding herbicides that are labeled for certain subtropical crops can be a bigger challenge. UC Weed Science has updated the Subtropical Crops herbicides usage chart for California growers (Fig. 1 Attachment below). It also seems that preventive programs are most frequently overlooked as a method of weed control. Preventive programs entail the use of such practices as sanitation, spot spraying, or hand labor to prevent the source of weed infestation (seed and/or vegetative) from widespread dissemination throughout a given area. By removing the undesirable weed species prior to seed development, dissemination by wind or mechanical transport on equipment can be effectively delayed.
Weed control programs will vary from location to location within the state and can even vary within a given site based upon specific conditions such as soil type, variety, method of herbicide application, and the presence of specific weed species.
Before herbicide application, growers should survey the grove and determine the stage of growth and type of weeds for that given location. Many products do not provide control of emerged species, thus requiring the application of more than one product to provide both preemergence and postemergence protection (Futch 2001). Rotation of soil-applied herbicides should also be considered to prevent the buildup of resistant annual and perennial weeds. The resistant species may not be evident initially; however, if the same herbicide and cultural program is maintained, over time their populations may build up until they infest the entire grove and become the dominant weed species (Jordan et al 1992).
Herbicide damage to foliage and fruit has also been noted when herbicides were applied under windy conditions or use of improper equipment allowed the materials to contact areas other than the weeds or soil. Please make sure to follow the label's direction and use caution.
Attached below is a chart listing herbicides registered for avocado, citrus, date, kiwi, fig and pomegranate.
Figure 1. Herbicide Registration on CA Subtropical Crops