Glenn C Wright

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• Wright, G. C. (2025).

  Date Production in Brazil

  . In Date Palm Cultivation in the Southern Hemisphere(pp 68-73). Abu Dhabi: © Khalifa International Award for Date Palm and Agricultural Innovation, affiliated with Erth Zayed Philanthropies Foundation, UAE Presidential Court,.
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  While date palms (Portuguese – “tamareira”) have been in Brazil for about 100 years, commercial interest in a Brazilian date industry developed about 40 years ago. An initial burst of research on dates slowed as priorities changed, but information gainedis still readily available. There are just two small commercial producers of date fruit (Portuguese – “Tâmara”) in Brazil based on an internet search. Both may have difficulty maturing their fruits on the palms due to relatively cool temperatures at harvest.A new initiative to plant date palms in trial locations around northeast Brazil was initiated by authorities from Brazil and the UAE in 2025. This seems to be a promising start to reinvigorate the industry. Date imports have increased greatly in the last 40 years, so there seems to be an opportunity to see if the hurdles can be overcome.
• Wright, G. C. (2025).

  Date Production in Paraguay

  . In Date Palm Cultivation in the Southern Hemisphere(pp 114-121). Abu Dhabi: © Khalifa International Award for Date Palm and Agricultural Innovation, affiliated with Erth Zayed Philanthropies Foundation, UAE Presidential Court,.
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  Among the regions of Paraguay, only the Chaco region, an arid steppe in the northwestern part of the country is suitable for growing date palms (Spanish – “Palma datilera”). These palms arrived sporadically as seedlings from about 1950 to 2000,but the first significant planting of Mejhoul dates occurred in 2019. Today, La Herencia S.A. farms 24 hectares of palms with an ultimate goal of 300 hectares of trees in about 20 years. There do not appear to be any other significant producers of the date fruit (Spanish – “dátil”) in Paraguay. There are a few disease problems, and worker acquisition and retention are challenges. Government support is minimal. Nevertheless,thereappeartobesignificant opportunities to sell the fruit in the national market and in the markets of nearby Brazil and Argentina.
• Wright, G. C. (2023). Organic Date Production. In Date Palm - CABI Crop Production Science in Horticulture. Wallingford, UK: CABI. doi:https://doi.org/10.1079/9781800620209.0011
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  Dates have been grown organically for thousands of years. Only relatively recently have certification procedures been developed to guide organic date producers. These procedures vary according to the certification authority but require at the outset the development and submission of an organic plan that describes the organic date orchard and the procedures that will be undertaken to achieve organic status. Once the decision has been made to grow organically, the planting, fertilization, cover crop establishment, and pest control steps must all be organic. Each certification authority has a list of allowed and prohibited substances that must be followed to remain organically certified. Organic procedures must continue during harvest and in the packinghouse. Fruit quality of an organic date does not appear to be inferior to a conventionally grown date, and some feel that organic dates have superior fruit quality. The economics of growing organic dates have not been studied; however, there is no doubt that the price received by the grower for organic dates is superior to that for conventional dates, which may overcome the higher cost of organic production. It is likely that organic dates will command an increasing portion of the overall date market.
• Wright, G. C. (2016). Citrus Care. In Arizona Master Gardener Handbook.
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  This is finished, and in press.

Journals/Publications

• Roose, M., Seymour, D., Kahn, T., Wright, G. C., Federici, C., Siebert Wooldridge, T., Trunelle, K., & Thomas, Z. (2025).

  DNA Markers Facilitate the UCR Citrus Breeding Program

  . Citrograph, 16(3), 64-68.
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  The University of California, Riverside (UCR) Citrus Breeding Program develops new scion and rootstock varieties for the California citrus industry. Breeding can be conducted more efficiently and effectively if we know more about the genetic material in parents and offspring. Here we describe DNA markers, an important technology we use to select hybrid seedlings, determine the frequency of nucellar seedlings in potential rootstock varieties and solve practical problems that arise in field trials. 
• Wright, G. C. (2025). CITRUS GREENING DISEASE (HUANGLONGBING) IN THE SOUTHWESTERN USA. Outlooks on Pest Management, 36(Issue 3). doi:10.1564/v36_jun_04
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  Citrus greening disease (CG), also known as Huanglongbing (HLB), is generally acknowledged as the most destructive citrus disease known, eclipsing the worst citrus tristeza virus outbreaks in the early 20th century. This article will describe CG and its vector and describe its effects on citrus trees and the citrus industry in the United States. Comparisons of disease spread in tropical and sub-tropical areas such as Florida with spread in the Mediterranean and desert climactic zones, which are similar to those found in the Middle East and North Africa (MENA) will be made. Additionally, successful methods used to slow the spread of the disease in the USA will be presented and some suggestions will be made that may slow the movement of CG into the MENA and reduce its impact upon arrival.
• Wright, G. C. (2025). Ciatrus Greening (Huanglongbing) in the Southwestern USA. Arab and Near East Plant Protection Bulletin, 94(1), 4-8.
• Wright, G. C., Pate, C., & Hu, J. (2025).

  Use of Drones to Determine Fungicide Efficiency in Lemon Orchards

  . Citrograph, 16(4), 58-62.
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  We are finding an increasing incidence of wood rot fungal diseases in desert lemons. The current recommendation is to prune out all infected wood and remove it from the orchard since there are no fungicides registered for these diseases. However, after laboratory and small plot tests in Arizona, we have identified nine candidate fungicides that reduce the incidence of the diseases. To determine the efficiency of the fungicides in commercial orchards, we are using drone technology to collect before- and after-application images across visible and nonvisible wavelengths for several thousand trees. These images are geolocated and combined to form a vegetation index for each tree. After ground truthing and categorization of the trees based on their index, preliminary results showed that several of the fungicides led to improved tree health. Successful selection of efficacious fungicides and their application by growers is expected to lead to improved orchard health, production and returns.
• Kahn, T., Seymour, D., Roose, M., Wright, G., & Mauk, P. (2024). Breeding Program Yields New Cultivars. Citrograph, 15(3), 41-44.
• Wright, G. C. (2024). Streamlining global germplasm exchange: Integrating scientific rigor and common sense to exclude phantom agents from regulation. Plant Disease, 1-20. doi:https://doi.org/10.1094/PDIS-04-24-0745-FE
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  Plant virology was established as a discipline in the late nineteenthcentury after the discovery of a novel entity causing tobacco mosaicdisease described as “contagium vivum fluidum” (Beijerinck 1898).Since then, the field has undergone tremendous progress in understandingplant viruses and the diseases they cause. Accurate laboratorydiagnostic tools, developed for the detection and identification ofviruses and other systemic pathogens (e.g. viroids, phytoplasmas, andfastidious bacteria) in plants, have advanced our understanding ofpathogen-vector-host interactions and are regularly employed in theproduction of plants that are free from regulated pathogens. Clean plantsare crucial for the sustainable production of clonally propagated crops(Gergerich et al. 2015; Hammond et al. 2023), facilitating the safe exchangeof plant material globally, and are often the basis of national orregional certification programs. Although accurate diagnostic tools arecrucial for certification programs and for facilitating the safe exchange ofplant material, current lists of regulated pathogens contain several“phantom” agents, which impede access to that material. Phantom agentshave been associated with symptomatic plants and diseases of unknownetiology. Most are presumed to be of viral nature, yet (i) neither infectedplant material nor reference isolates are available and (ii) no sequenceinformation is accessible. The majority of the phantom agents listedamong regulated pathogens are the result of a single report that describessymptoms and/or names a purported pathogen in the scientific literature.It is worth noting that many of the agents discussed herein have only beenreported in scientific conference abstracts and proceedings and have notgone through the peer-review process. It is often futile to state the obvious,but for the purpose of this communication, it is important to rememberthat diagnosing a disease or detecting an agent that is alleged toexist but might not be real is impossible. Biological indexing is, otherthan in a very few exceptions, used to identify phantom agents. However,biological indexing is not the most appropriate of all available diagnosticstechnologies for clonally propagated crops, including thosecovered herein (Al Rwahnih et al. 2015; Bester et al. 2021; Rott et al.2017; Villamor et al. 2022). However, when symptoms develop ingrafted indicator plants, it is often impossible to determine whether theindexed agent is one of the so-called phantoms, owing to the absence of apositive control. With today’s technology, if an indicator plant showssymptoms, it would undergo analysis by high-throughput sequencing(HTS). If this process identifies a novel agent, it is unlikely to be attributedto a phantom. Instead, it would be recognized as a new pathogenof the host. As a result, phantom agents tend to persist indefinitely. In thecase of phantom agents and the disease they were named for, it is impossibleto determine whether the disease is real and, if so, whether it iscaused by a single or multiple agents or an agent known under a differentname or even whether the said agent has been eliminated from the cropbecause of extensive sanitation and testing through certification programs,or the incorporation of resistance in modern cultivars. Subject experts fromaround the globe joined efforts in reviewing the relevant literature in theirareas of expertise and prepared a list of phantom agents/diseases for10 vegetatively propagated plant genera, grouped in eight crops. Based onour collective assessment and knowledge, we recommend that phantomagents and diseases be removed from regulatory lists based on the inabilityto (i) access diseased plant material/identify an agent (isolate) and (ii)obtain sequence information that would allow for their identification andthe development of diagnostics. When we initiated this project, the coregroup of individuals named as the primary coauthors identified more than140 agents. Communications with individuals from around the globe havetriggered research efforts that have led to the identification of type isolatesfor some of these agents and characterization of others. A list of characterizedagents is provided in Table 1. Herein, we provide information onmore than 120 phantom agents/diseases for major clonally propagatedcrops and discuss why requiring their diagnosis from a biological perspectiveis unsound. Every disease/agent discussed herein fits the aforementioneddefinition of a phantom agent.
• Wright, G. C., & Hu, J. (2024). First Report of Neodeightonia phoenicum Causing Black Scorch and Rot Disease on Date Palms in Arizona. Plant Disease. doi:https://doi.org/10.1094/PDIS-02-24-0491-PDN
• Wright, G., Roose, M., Seymour, D., Federici, C., Siebert-Wooldridge, T., Trunnelle, K., Thomas, Z., & Kahn, T. (2024). Optimizing Lemon Production. Citrograph, 15(3), 64-69.
• Wright, G. (2023). Status of the date palm industry in the United States. Acta Horticulturae, 1371, 1429-1433.
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  Despite being ranked 16th in world date production, the United States has a vibrant and progressive date palm industry. In 2020, almost 57,000 MT were produced, mostly of the ‘Deglet Noor’ and ‘Medjool’ cultivars, valued at almost USD$ 200,000,000. Domestic date consumption is slowly increasing, while a significant portion of the crop is exported. Imports play a key role as well. This presentation will include the most up-to-date production, consumption, import and export statistics. Details of the actions that US date producers are taking to decrease production costs and increase sustainability will be presented. Also, results from a survey of consumer preferences and subsequent measures that are being launched to increase domestic consumption of fresh fruit and value-added products will be highlighted. Finally, the status of several insect and disease pests that threaten the industry will be detailed.
• Wright, G. C. (2023). Mejhoul cultivation in the USA. Acta Horticulturae, 1371, 5-8. doi:10.17660/ActaHortic.2023.1371.2
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  Dates have been grown in the United States for over 200 years. Large plantings began about 125 years ago and the ‘Mejhoul’ was imported successfully in 1927. The US ‘Mejhoul’ industry began with a 23-ha planting in 1945, near Bard, CA, and has grown to several thousand ha today. Trees are planted in several types of soils, at spacings ranging from 7.5 to 9 m2. Irrigation is by flood or pressurized systems, and most fertilization is applied via the irrigation water. ‘Mejhoul’ dates are pollinated and thinned, then bagged before harvest. Harvest begins in August and continues through October. Few pests are problematic on ‘Mejhoul’. Harvested dates are sorted for color, dried to consistent moisture, sorted again for quality, and then shipped fresh or frozen if needed. US ‘Mejhoul’ dates are exported to Canada, Australia, Mexico, and other countries, while the US imports ‘Mejhoul’ dates from Mexico, Israel, and other countries. Date consumption in the US is low but has increased by 50% since 2012 due to active marketing programs.
• Wright, G. C., Kahn, T., & Mikeal, R. (2023). Yield, packout and fruit quality results from four lemon cultivar trials in California

   

  . Acta Horticulturae, 1366, 121-130. doi:https://doi.org/10.17660/ActaHortic.2023.1366.14
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  We established four lemon cultivar trials in California in 2015. Trial locations included the cooler San Joaquin Valley, and Coastal region, and the warmer inland Southern California, and the California desert. Cultivars evaluated included ‘Limoneira 8A Lisbon’, low-seeded ‘Limoneira 8A IR1 Lisbon’, ‘Walker Lisbon’, Corona Foothills’, ‘Limonero Fino 49’, and ‘Yen Ben’. Rootstocks varied by location. In the cooler locations, ‘Walker Lisbon’ had the greatest yield, followed closely by ‘Limoneira 8A Lisbon’. In warmer areas, ‘Corona Foothills,’ ‘Limonero Fino 49’, ‘Limoneira 8A Lisbon’ and ‘Walker Lisbon’ had the greatest yield. Yields of low-seeded ‘Limoneira 8A IR1 were 20 to 50% less, depending on location, than its seeded counterpart and yields of ‘Yen Ben’ were poor at every location because of smaller tree size. In some cases, the yield differences may have been due to incompatibility between the cultivar and rootstock, or to effects of soil pH. Fruit size of ‘Limoneira 8A IR1 Lisbon’ were often larger than the others, while fruit of ‘Yen Ben’ were often quite small. There were minor differences in fruit quality among the cultivars, except for ‘Yen Ben’ that had smoother and thinner peel.
• Hu, J., & Wright, G. (2022). Canker and wood rot pathogens present in young lemon orchards in south-west Arizona. Plant Pathology, 71(2). doi:10.1111/ppa.13476
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  Canker and wood rots are economically important preharvest diseases of lemons in south-western Arizona, where commercial lemon production is concentrated. However, the aetiology and epidemiology of canker and wood rots are not well understood. This study comprised a large survey of canker and wood rot incidence and severity in Arizona and the characterization of fungal species associated with the disease. A total of 5431 trees with ages ranging from 1 to 20 years old in 10 lemon orchards were surveyed from 2018 to 2020. Our survey results revealed that canker and wood rot occurred in all 10 lemon orchards studied. Canker and brown rots of twigs, branches, and trunks were the most prevalent symptoms of affected trees ranging from 1 to 20 years old. In contrast, canker and white rots of twigs and branches were observed mostly on 1- to 5-year-old trees. Disease incidence for both diseases was less than 2% on 1- and 2-year-old trees. Brown rot increased significantly in older trees, ranging from 62.9% to 100%. Fungi were isolated from canker and wood rot samples and identified based on morphological characters and DNA sequences. Fomitopsis meliae and Hypoxylon macrocarpum were the primary canker and wood rot pathogens isolated from the surveyed orchards, at frequencies of 89% and 11%, respectively. In pathogenicity tests, both fungi were capable of causing canker and wood rots on lemon cv. Lisbon branches and the necrotic length caused by F. meliae was twofold greater than that caused by H. macrocarpum.
• Salomón-Torres, R., Ortiz-Uribe, N., Krueger, R., García-Vázquez, J. P., Cohen, Y., Wright, G. C., & Samaniego-Sandoval, L. (2022). Evaluation of Pollen Production of Common Male Date Palms Grown in the Mexicali Valley, Mexico. Agriculture, 12(8), 1248. doi:https://doi.org/10.3390/agriculture12081248
• Hu, J., & Wright, G. C. (2021). First Report of Fomitopsis meliae Causing Brown Wood Rot on Living Lemon Trees in Arizona and California. Plant Disease. doi:10.1094/PDIS-11-20-2427-PDN
• Kahn, T. L., Vince, S., & Wright, G. C. (2021). Lemon Returns - Final Summary of the California Desert Lemon Trial. Citrograph, 12(3), 36-45.
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  Deciding which lemon selection to grow is an important factor in maximizing returns. This lemon trial for the California Desert, conducted from 2005-06 through 2018-19, was the first trial that collected fruit quality characteristics, yield, pack-out data and estimated cumulative returns per acre to compare the commercial potential of ten lemon selections against two California commercial standards.
• Wright, G. C., Lovatt, C., & Eskalen, A. (2021). Air Temperature and Stress May Lead to Pre-Harvest Lemon Fruit Drop. Citrograph, 12(4), 38-42.
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  Pre-harvest lemon fruit drop (LFD) occurs when full-sized fruit fall from apparently healthy trees. Significant economic loss can occur. We identified potential factors that might lead to LFD, including presence of fungi on the fruit and in the soil, leaf mineral deficiencies and climactic conditions. In 2018 and 2019, we collected soil, fruit and leaf samples in California and Arizona orchards, and we applied plant growth regulators (PGRs), fungicides and mineral nutrients to attempt drop reduction. In both years, neither leaf mineral nutrient concentrations nor soil and fruit pathogen sampling results correlated to LFD. Fungicide and PGR treatments applied did not affect LFD counts or orchard yields. Data suggest that temperature may be the primary cause of LFD, especially for early bloom fruit. Harvesting earlier appeared to reduce LFD, which occurred shortly after daily maximum temperatures dropped due to the reduction of the Southwestern Monsoon. With this new insight, research to determine the proper time for PGR application is needed.
• Stover, E., & Wright, G. C. (2019). Walter Tennyson Swingle: A Relentless Intellect that Transformed American Pomology. Journal of the American Pomological Society, 73(2), 129-138.
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  Walter Tennyson Swingle grew up outside of Manhattan, Kansas, attended classes at Kansas State Agricultural College (now KSU) at 15, and when he graduated at 20 he had already published 27 scientific papers in plant pathology, plant breeding and genetics. Swingle joined the United States Department of Agriculture (USDA) in 1891, and was sent to Florida to investigate diseases in orange trees. He established a USDA laboratory and began a comprehensive program to breed disease- and frost-resistant citrus. He proposed testing all known wild relatives for disease-resistance and other advantageous traits that could be introduced to improve citrus. While conducting comprehensive studies of the comparative anatomy and systematics of the orange subfamily, he discovered some new species and several new genera. His breeding originated several new categories of citrus: the tangelos, citranges and citrumelos (now critical as rootstocks), and many other intergeneric hybrids. He was an early advocate for permanent, living collections of economically important plants and their close relatives. In 1897-98, in collaboration with David Fairchild, he established the USDA's Office of Foreign Seed and Plant Introduction, and new plant introduction research facilities were set up in Miami. He was a champion for ensuring that introduced plants were disease and pest free. He conducted plant exploration, mainly in countries surrounding the Mediterranean, and among many other accessions introduced date palms, figs, table grapes, and ‘Clementine’ mandarins. He also brought in the Blastophaga wasp to pollinate Smyrna-type figs. After his retirement from the USDA, Swingle moved to Miami in 1943 and completed his treatise on the taxonomy of the citrus subfamily. “Even in his retirement, Swingle inspired a generation of students with his knowledge, curiosity of nature, and insights into plants. His simple advice to students was ‘Look and look, again and again,’ words still relevant today”.
• Wright, G. C., & Hu, J. (2019). Huanglongbing of Citrus. University of Arizona Cooperative Extension Publication, 7. doi:https://extension.arizona.edu/pubs/huanglongbing-citrus
• Bidabadi, S. S., Dehghanipoodeh, S., & Wright, G. C. (2017). Vermicompost leachate reduces some negative effects of salt stress in pomegranate. International Journal of Recycling of Organic Waste in Agriculture, 6, 1-9. doi:10.1007/s40093-017-0173-7
• Wright, G. C. (2016). The Commercial Date Industry in the United States and Mexico. HORTSCIENCE, 51(11), 1333-1338.
• Wright, G. C. (2016). The commercial date industry in the United States and Mexico. HortScience, 51(Issue 11). doi:10.21273/hortsci11043-16
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  The date palm(Phoenix dactyliferaL.) originated in theArabianPeninsula, spread throughout North Africa, then was carried to Mexico and the United States. Planting began in earnest in Arizona and California in the late 1800s and continues today. As of 2014, date production in Mexico and the United States is valued at almost $13,000,000, and comprises about 7400 ha. ‘Deglet Noor’ and ‘Medjool’ are the major cultivars. Modern practices for date palm cultivation include planting, irrigation, fertilization, pollination, thinning the fruit, ringing the bunches, bagging the bunches, and harvest. After harvest, the fruit must be sorted, dried or rehydrated, and graded. Date palms are sometimes sold for landscaping purposes. Current research at the University of Arizona and University of California at Riverside is focused on pollination and thinning practices, improving fruit quality and controlling insects. There are four date palm germplasm collections located in Arizona and California.
• Kahn, T. L., Samons, V., & Wright, G. C. (2015). When life gives you lemons, it's time to make a profit.. Citrograph, 6(3), 48-59.
• Kahn, T., & Wright, G. (2015). Update on Evaluations of Lemon Selections for the California Desert. HortScience, 50(9), S189 (Abstr.).
• Wright, G. C. (2015). Area-Wide Spraying for Asian Citrus Psyllid in Texas and Florida. CALS Publications Archive. The University of Arizona..
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  Realizing that the Arizona citrus industry might someday have to deal with widespread ACP control, the Arizona Citrus Research Council approved a trip to Florida and Texas to investigate how ACP control was accomplished in those two states. The trips were to McAllen, Texas on 9-12 Nov 2011 and to Immokalee Florida on 17-18 Nov. 2011. In McAllen, I interviewed Dr. Mamoudou Setamou, extension entomologist for Texas A&M – Kingsville and his staff, and Mr. Ray Prewitt, president of Texas Citrus Mutual. In Florida, I interviewed Mr. Ron Hamel, manager of the Gulf Citrus Growers, and Dr. Mongi Zekri, southwest Florida Multi-County Citrus Agent, housed at the Hendry County Extension Office in LaBelle., FL. The author hopes that some of this information can be used in the development of an Area Wide Spray Plan in Arizona.
• Wright, G. C. (2015). Control of Brown Wood Rot in Lemons with Low Pressure Injection 2013-14. CALS Publications Archive. The University of Arizona..
• Wright, G. C. (2015). Evaluation of Nitrogen Fertilization Practices for Surface-Irrigated Lemon Trees - 2012. CALS Publications Archive. The University of Arizona..
• Wright, G. C., & Schuch, U. K. (2015). Pomegranate Variety Trial in Arizona. HortScience, 50(9), S309 (Abstr.).
• Wright, G., & Caravetta, G. (2014). Response of Government and the Citrus Industry to the Discovery of Asian Citrus Psyllid in Arizona. Journal of Citrus Pathology, 1(1), 80.
• Schuch, U. K., Wright, G. C., & Mahato, T. (2013). Pomegranate Variety Trial in Southern Arizona.. HortScience, 48(9), 396.
• Wright, G. (2012). Date Cultivation in Arizona and the Bard Valley. J. Amer. Pom. Soc, 66(3), 110-117.
• Wright, G. (2012). Nitrogen Fertilization Guidelines for Non- bearing Medjool Date Palms. HortScience, 47(9), S305.
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  HortSci
• Wright, G. C. (2008). Evaluation of ten navel orange (Citrus sinensis) selections under Arizona desert conditions. Acta Horticulturae, 773, 77-82.
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  Abstract: A navel orange (Citrus sinensis) trial was established at the University of Arizona Citrus Agriculture Center, Waddell, AZ in 1999. This trial consists of the following selections: 'Beck-Earli', 'Cara Cara', 'Chislett', 'Fisher', 'Fukumoto', 'Lane Late', 'Powell', 'Spring', 'Washington' and 'Zimmerman', all on Carrizo citrange rootstock. 'Washington' is the standard cultivar selection for the local industry. Yield, packout and fruit quality data have been collected since the first harvest in 2001. 'Fisher', 'Lane Late', 'Beck-Earli' and 'Washington' have had the greatest 5-year cumulative yield, and those selections as well as 'Cara Cara' had good annual yields in 2005-06. 'Beck-Earli' and 'Chislett' have had good yields for the 2004-05 seasons. 'Beck-Earli', 'Chislett', and 'Lane Late' generally have had large fruit size over the course of the experiment. 'Zimmerman', 'Cara Cara' and 'Washington' had large fruit size in 2004-05. 'Beck-Earli' has had characteristically elongated fruit, while the rest of the selections have had more rounded fruit. Among the early-harvest fruit, 'Fisher' is the least colored, and 'Fukumoto' colors the best. 'Spring' fruit has the best color among those selections harvested late. 'Cara Cara' fruit typically has had the highest level of solids, while the late navels have lower levels of solids. Peel thickness and granulation of the selections varies depending on the year. Based on the data collected so far, 'Beck-Earli', 'Cara Cara', 'Chislett', 'Fisher', 'Fukumoto' and 'Lane Late' appear to be suitable alternatives to 'Washington' in the desert.
• Wright, G. C. (2007). AN OVERVIEW OF THE CHANGING DATE INDUSTRY IN THE UNITED STATES. Acta Horticulturae, 736(736), 47-52. doi:10.17660/actahortic.2007.736.2
• Wright, G. C. (2007). An overview of the changing date industry in the United States. Acta Horticulturae, 736, 47-52.
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  Abstract: The commercial date industry in the United States is located primarily in the Sonoran Desert of southeast California and southwest Arizona. The industry comprises about 3800 hectares, of which 78% is found in California and the rest in Arizona. While date palms were introduced to the United States by the Spaniards, small quantities were imported for experimental purposes beginning in the late 1800's, and commercial quantities were imported in the early 1900's. During this period, most imported offshoots originated from Algeria, Egypt, Tunisia and Iraq. Important varieties that were imported include 'Deglet Noor', 'Khadrawi', 'Zahidi', 'Hayany' and 'Halawy'. More recently, the 'Medjool' from Morocco was introduced. This variety is becoming increasingly popular because of its large size and high sugar content. Date palm operations are moving from areas that are under pressure from urbanization to more remote locales. Low volume drip and microjet irrigation is beginning to replace the tradition flood and basin irrigation methods. Some dates are produced using organic methods because of consumer demand. Farm operations begin in January when the trees are dethorned. Operations that occur later in the year include pollination, training the fruit arms, strand thinning, fruit thinning, supporting the arms, spreading the strands, bagging the developing fruit and harvest. Individual growers are increasingly forming cooperatives to pack the fruit at a centrally located packinghouse. At the house, fruit are graded, then packed, and placed in storage until shipment. Dates from the region are marketed by individual growers, and by the grower cooperatives, and sold to customers around the world. Palm trees are also sold for landscape purposes to customers across the United States.
• Wright, G. C., & Pena, M. A. (2007). Lemon Rootstock Trials in Arizona - 2006-07. Citrus Research Report.
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  In a rootstock evaluation trial planted in 1993, five rootstocks, ‘Carrizo’ citrange, Citrus macrophylla, ‘Rough Lemon’, Swingle citrumelo and Citrus volkameriana were selected for evaluation using 'Limoneira 8A Lisbon' as the scion. 1994-2006 yield and packout results indicate that trees on C. macrophylla, C. volkameriana and ‘Rough Lemon’ are superior to those on other rootstocks in both growth and yield. C. macrophylla does not consistently outperform C. volkameriana. ‘Swingle’ and Carrizo’ are performing poorly.
• Kusakabe, A., White, S. A., Walworth, J. L., Wright, G. C., & Thompson, T. L. (2006). Response of microsprinkler-irrigated navel oranges to fertigated nitrogen rate and frequency. Soil Science Society of America Journal, 70(5), 1623-1628.
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  Abstract: Microsprinklers allow precise control of irrigation water applications and offer the potential for higher efficiency of water and fertilizer use compared with flood irrigation. A field experiment was conducted during 1999-2002 in central Arizona (AZ) to evaluate effects of various N rates and fertigation frequencies on fruit yield and quality, leaf N concentration, and residual soil N of 'Newhall' navel oranges (Citrus sinensis) on 'Carrizo' citrange (Porcirus trifoliata x Citrus sinensis) rootstock (planted in 1997) grown in a Gilman (coarse-loamy, mixed, superactive, calcareous, hyperthermic Typic Torrifluvents) fine sandy loam. The experiment included nonfertilized control plots and factorial combinations of three fertigation frequencies (27, 9, and 3 applications annually) and three N rates (68, 136, and 204 g N tree-1 yr-1). Maximum yields occurred at N rates of 105 to 153 g N tree-1 yr-1 for the fourth to the sixth growing seasons. The yield-maximizing N rates were equivalent to 17 to 34% of currently recommended N rates for citrus grown in AZ. Fruit and juice quality did not show significant response to N rate or fertigation frequency. Leaf N concentrations at yield-maximizing N rates were above the critical leaf tissue N range of 25 to 27 mg g-1, indicating that this range may be too low for these 'Newhall' navel orange trees. During all three seasons, higher residual soil NO3 concentrations resulted from the highest N rate. Our results suggest that optimum N rates for microsprinkler-irrigated 'Newhall' navel oranges in AZ are lower than currently recommended N rates. © Soil Science Society of America.
• Wright, G. C. (2005). Lemon Cultivar Selection Trials in Arizona. Hortscience, 40(4), 1108-1108. doi:10.21273/hortsci.40.4.1108b
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  Two lemon [Citrus limon (L.) Burm.] cultivar selection trials are being conducted at the Yuma Mesa Agriculture Center in Somerton, Ariz. Some selections in these trials include: `Allen Eureka', `Berna', `Cook Eureka', `Cascade Eureka', `Cavers Lisbon', `Strong Lisbon', `Femminello Comune', `Lapithkiotiki', `Limoneira 8A Lisbon', `Limonero Fino 49', `Monroe Lisbon', `Primofiori', `Santa Teresa', `Walker Lisbon', and `Villafranca'. Selections that have had superior yields include `Cascade Eureka', `Cook Eureka', `Strong Lisbon', `Limoneira 8A Lisbon', `Limonero Fino 49', `Primofiori', `Femminello Comune', and `Villafranca'. Fruit size data suggest that `Limonero Fino 49' has consistently good fruit size, and consistently larger fruit than `Limoneira 8A', the industry standard. `Cavers Lisbon' and `Femminello Comune' also have good fruit size. `Lapithkiotiki' also had large fruit size, but its shape was unacceptably elongated. We also found significant differences in peel thickness and juice pH among the selections. `Santa Teresa' had significantly lower juice pH and a thinner peel than some of the other selections under evaluation.
• Wright, G. C., & Poe, S. E. (2005). 149) Arizona Farm Safety Day. Hortscience, 40(4), 1045-1045. doi:10.21273/hortsci.40.4.1045b
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  Arizona Farm Safety Day has been held annually since 2000 as an attempt to educate students and farm workers (pesticide applicators, tractor and equipment operators, irrigators, and field workers) in farm safety. Our programs have emphasized tractor safety, pesticide safety, ATV safety, electrical safety, and firearms safety. The all-day events have been held in Yuma and in Safford, Ariz., and most of the attendees are high school students. Agriculture students from six to eight high schools typically participate. The agenda is determined by consulting with local agriculture leaders. Attendees have the opportunity to attend a 4-hour training session in the morning. Subjects taught at these sessions might include reading a pesticide label, sprayer calibration, wearing proper protection, avoiding spray drift, tractor safety, and farm safety. At least one of these sessions is an outdoors “hands-on” session. Individual participants receive up-to-date information and literature, a certificate of completion, CEUs, CCA credits, a hat, and a lunch. Spanish translation is available at each session. In the afternoon, a tractor driver safety course and equipment demonstration is typically held. In the course, selected representatives from local farms or local youth get a chance to demonstrate their tractor and ATV driving and safety skills for recognition and awards. Plaques and trophies are awarded to the winners. Additionally, there is an equipment demonstration. Attendees are tested before and after the event.
• Mccloskey, W. B., Rector, R. J., Sumner, C., & Wright, G. C. (2003). Citrus Orchard Floor Management 2001-2003: Comparison of a Disk, “Perfecta” Cultivator, and Weed Sensing Sprayer. Citrus Research Report.
• Wright, G. C., & Pena, M. A. (2003). Established ‘Lisbon’ Lemon Trials in Arizona – 2002-03. Citrus Research Report.
• Wright, G. C., & Pena, M. A. (2003). Results of New Cultivar Selection Trials for Orange in Arizona - 2003. Citrus Research Report.
• Wright, G. C., McCloskey, W. B., & Taylor, K. C. (2003). Managing orchard floor vegetation in flood-irrigated citrus groves. HortTechnology, 13(4), 668-677.
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  Abstract: Several orchard floor management strategies were evaluated beginning in Fall 1993 in a 'Limoneira 8A Lisbon' lemon (Citrus limon) grove on the Yuma Mesa in Yuma, Ariz. and in a 'Valencia' orange (Citrus sinensis) grove at the University of Arizona Citrus Agricultural Center, Waddell, Ariz. At Yuma, disking provided acceptable weed control except underneath the tree canopies where bermudagrass (Cynodon dactylon), purple nutsedge (Cyperus rotundus), and other weed species survived. Mowing the orchard floor suppressed broadleaf weed species allowing the spread of grasses, primarily bermudagrass. Preemergence (norflurazon and oryzalin) and postemergence (glyphosate and sethoxydim) herbicides were used to control weeds in the clean culture treatment in Yuma. After three harvest seasons (1994-95 through 1996-97), the cumulative yield of the clean culture treatment was 385 kg (848.8 lb) per tree, which was significantly greater than the 332 kg (731.9 lb) and 320 kg (705.5 lb) per tree harvested in the disking and mowing treatments, respectively. In addition, the clean culture treatment had a significantly greater percentage of fruit in the 115 and larger size category at the first harvest of the 1995-96 season than either the disk or mow treatments. At Waddell, the management strategies compared were clean culture (at this location only postemergence herbicides were used), mowing of resident weeds with a vegetation-free strip in the tree row, and a 'Salina' strawberry clover (Trifolium fragiferum) cover crop with a vegetation-free strip. The cumulative 3-year yield (1994-95 through 1996-97) of the clean culture treatment was 131 kg (288.8 lb) per tree, which was significantly greater then the 110 kg (242.5 lb) per tree yield of the mowed resident weed treatment. The yield of the strawberry clover treatment, 115 kg (253.5 lb) of oranges per tree, was not significantly different from the other two treatments. The presence of cover crops or weeds on the orchard floor was found to have beneficial effects on soil nitrogen and soil organic matter content, but no effect on orange leaf nutrient content. The decrease in yield in the disked or mowed resident weed treatments compared to the clean culture treatment in both locations was attributed to competition for water.
• Mccloskey, W. B., Wright, G. C., & Sumner, C. P. (2002). Citrus Orchard Floor Management 2001: Comparison of a Disk, "Perfecta" Cultivator, and Weed Sensing Sprayer. Citrus Research Report.
• Rector, R. J., Mccloskey, W. B., Wright, G. C., Sumner, C., & Sumner, C. P. (2002). Citrus Orchard Floor Management 2001: Comparison of a Disk, "Perfecta" Cultivator, and Weed Sensing Sprayer. Citrus and Deciduous Fruit and Nut Research Report.
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  An optical weed sensing sprayer (WeedSeeker) was evaluated for making postemergence glyphosate herbicide applications in a Yuma, AZ lemon orchard. In addition, mechanical (disk and Perfecta cultivator) and chemical weed control strategies were compared. Results were fairly similar; however, the use of the WeedSeeker units combined with a preemergence herbicide (H1) increased weed control three fold compared to disking (D) and perfecta (P1). Additionally, when the WeedSeeker units were used in conjunction with preemergence herbicides, spray volume was reduced by 66% compared to a conventional sprayer and by 57% when used for postemergence applications only. There was a relationship between weed ground cover and the area sprayed by the WeedSeeker units indicating that maximum postemergence herbicide savings will occur at low weed densities or less than 10% groundcover. The use of a sprayer with an improved suspension system allowed for faster spraying speeds than were possible with the tractor mounted sprayer. Weed control was similar for the conventional and the WeedSeeker sprayer. However, yields were variable for both years. Future investigations will include efforts to develop crop budgets based on experimental operations.
• Wright, G. C., & Pena, M. A. (2002). Established 'Lisbon' Lemon Trials in Arizona - 2001-02. Citrus and Deciduous Fruit and Nut Research Report.
• Wright, G. C., & Pena, M. A. (2002). Foliar applications of Lo-Biuret Urea and Potassium Phosphite to Navel Orange Trees. Citrus and Deciduous Fruit and Nut Research Report.
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  This experiment was established in January 2000 in a block of ‘Washington’ navel orange trees at Verde Growers, Stanfield, AZ. Treatments included: normal grower practice, winter low biuret (LB) urea application, summer LB urea application, winter LB urea application plus winter and spring potassium phosphite, winter LB urea application plus summer potassium phosphite, and normal grower practice plus spring potassium phosphite. Each treatment was applied to approximately four acres of trees. For 2000-01, yields ranged from 40 to 45 lbs. per tree, and there was no effect of treatments upon total yield. There was a slight effect upon fruit size and grade. Trees subject to summer LB urea application had significantly more fruit of size 56, compared to trees subject to winter LB urea, and untreated, and untreated trees had significantly more fruit of size 88 than did treated trees. Also, treated trees had slightly more fruit in the fancy grade than did untreated trees. Introduction Arizona citrus growers face increasing economic and political pressure to adapt best management practices for nitrogen fertilization. Foliar N fertilization offers an opportunity to apply a significant portion of the total tree N needs in a more efficient manner than traditional flood or ground applications. Navel oranges typically do not bear in great abundance in the desert. Water stress during fruit set, and/or high temperatures during bloom or fruit set can cause yield reductions. Recent research by Lovatt suggests that pre-harvest applications of foliar urea and potassium phosphite can increase yield and fruit set on ‘Washington’ navel oranges in the San Joaquin Valley 1 The authors would like to than the Arizona Citrus Research Council for ongoing financial support necessary to complete this study. This is the final report for Project 2000-10 “Foliar applications of Lo-Biuret Urea and Potassium Phosphite to Navel Orange trees”. 2 Davies, F.S. 1986. The Navel orange. In: Janick, J. (ed.) Horticultural Reviews. AVI Publishing, Co., Westport, CT Pp. 79-99. 3 Lovatt, C.J. 1998. Managing yield with foliar fertilization. Calif. Citrograph 84:1. This is a part of publication az1275: "2001 Citrus and Deciduous Fruit and Nut Research Report," College of Agriculture and Life Sciences, the University of Arizona, Tucson, Arizona, 85721. Although relatively uncommon in Arizona, foliar macronutrient application to citrus is an increasingly common practice in California citrus groves. Research by Jones and Parker found that foliar urea application was a practical method of applying N as early as 1949. Foliar N fertilization did not find widespread commercial acceptance because of the fact that a minimum of three applications per year would be needed to supply the tree’s N requirements. However, Sharples and Hilgeman5 suggested that a single application of urea applied to ‘Valencia’ orange foliage at the phenologically appropriate time might improve yield in Arizona trees. 4 Jones, W.W. and E.R. Parker. 1949. Application of urea to foliage of orange trees. Calif. Citrograph 34:463. 5 Sharples, G.C. and R.H. Hilgeman. 1969. Influence of differential nitrogen fertilization on production, trunk growth, fruit size, quality and foliage composition of ‘Valencia’ orange trees in central Arizona. Proc. First Intl. Citrus Symposium 3: 1569-1578.
• Wright, G. C., & Pena, M. A. (2002). Results of 'Fallglo' Trials for Citrus in Arizona - 2001. Citrus and Deciduous Fruit and Nut Research Report.
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  A ‘Fallglo’ mandarin trial was established at the Yuma Mesa Agriculture Center in 1995. Results suggest that trees on C. volkameriana rootstock, rough lemon rootstock, and, in 2001-02, Gou Tou orange rootstock had the greatest yields. There was little effect of rootstock upon fruit size or juice quality.
• Wright, G. C., & Pena, M. A. (2002). Results of New Cultivar Selection Trials for Orange in Arizona - 2001. Citrus and Deciduous Fruit and Nut Research Report.
• Wright, G. C., & Pena, M. A. (2002). Results of Scion and Rootstock Trials for Citrus in Arizona - 2000. Citrus and Deciduous Fruit and Nut Research Report.
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  Five rootstocks, ‘Carrizo’ citrange, Citrus macrophylla, Rough lemon, Swingle citrumelo and Citrus volkameriana were selected for evaluation using 'Limoneira 8A Lisbon' as the scion. 1994-2000 results indicate that trees on C. macrophylla and C. volkameriana are superior to those on other rootstocks in both growth and yield. C. macrophylla is outperforming C. volkameriana. Rough lemon is intermediate, and ‘Swingle’ and Carrizo’ are performing poorly. For 2000-01, rough lemon trees performed similarly to C. macrophylla and C. volkameriana. In a similar trial, Four 'Lisbon' lemon selections, 'Frost Nucellar', 'Corona Foothills', 'Limoneira 8A' and 'Prior' were selected for evaluation on Citrus volkameriana rootstock. 1994-2001 results indicate that the 'Limoneira 8A Lisbon' and ‘Corona Foothills Lisbon’ are superior in yield and fruit earliness. Results from another lemon cultivar trial suggest that ‘Cavers Lisbon’, Limonero Fino 49’ and “Villafranca’ lemons may be good candidates for plantings as well. Results from three other lemon scion trials, a navel orange cultivar trial and a ‘Valencia’ orange trial, and a ‘Fallglo’ mandarin trial are presented as well.
• Zerkoune, M., Zerkoune, M., Wright, G. C., Kernz, D., & Mccloskey, W. B. (2002). Organic Lemon Production. Citrus Research Report.
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  This experiment was initiated in March 2000 to study the feasibility of growing organic lemon in the desert southwest of Arizona. A ten-acre field planted to lemons in 1998 was selected on Superstition sand at the Yuma Mesa Agricultural Research Center. The initial soil test in top 6 inches was 5 parts per million (ppm) NO3 and 4.9-PPM NaHCO3-extractable P. Soil pH was 8.7 in the top 6 inches. Seven treatments were applied in randomized complete block design repeated three times. The treatments were control, compost and clover, compost and perfecta, compost and steam, manure and clover, manure and perfecta and manure and steam Leaf tissue analysis indicated that nitrate level was significantly influenced by treatment. Organic insect control treatments for citrus thrips were as equally effective as the non-organic commercial standards.
• Demetriou, M. C., Thompson, G. A., Wright, G. C., & Taylor, K. C. (2000). A molecular approach for the diagnosis of wood rotting disease in desert citrus. Mycologia, 92(1-6), 1214-1219.
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  Abstract: Brown heartwood rot is an increasingly important problem in southwestern deserts, affecting numerous native tree species, and commercial lemon production. Two fungal pathogens, Coniophora eremophila and Antrodia sinuosa, have been identified as causal agents of brown heartwood rot in citrus. Development of effective disease management strategies relies on the ability to readily identify and distinguish between the pathogens; therefore we have developed molecular markers as an alternative to morphometric methods to differentiate these two economically important pathogens. Random amplified polymorphic DNA analysis identified four primers that revealed fungal polymorphisms. Polymorphic DNA fragments were cloned, sequenced, and used to create a 700 bp sequence characterized amplified region (SCAR) in C. eremophila isolates using sequence-specific primers, Conio7 and Conio8. Three fragments (300, 650, and 1000 bp) were amplified with Conio7 and Conio8 in A. sinuosa isolates. A rapid, small scale method for DNA extraction from fungus was developed to expedite the technique. With this method, the usefulness of the Conio7 and Conio8 was verified using new Coniophora eremophila and Antrodia sinuosa isolates from citrus.
• Fidelibus, M. W., Martin, C. A., Wright, G. C., & Stutz, J. C. (2000). Effect of arbuscular mycorrhizal (AM) fungal communities on growth of 'Volkamer' lemon in continually moist or periodically dry soil. Scientia Horticulturae, 84(1-2), 127-140.
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  Abstract: Citrus volkameriana Tan. and Pasq. ('Volkamer' lemon) seedlings were inoculated with five different communities of arbuscular mycorrhizal (AM) fungi collected from citrus orchards in Mesa and Yuma, AZ, USA, and undisturbed North American Sonoran Desert and Chihuahuan Desert soils. Plants were then grown in a glasshouse for four months under continually moist or periodically dry conditions achieved by altering watering frequency so that before watering events container soil water tensions were approximately -0.01 MPa (continually moist) or -0.06 MPa (periodically dry) one half way down the container profile. Plants grown in continually moist soil had greater shoot growth than plants grown in periodically dry soil. Plant P status did not limit growth, and there was no interaction between watering frequency and AM fungal inoculum treatments. Plants inoculated with AM fungi from the Yuma orchard soil had significantly less root dry weight and total root length, and lower photosynthetic fluxes than plants treated with inoculum from the other soils. Specific soil respiration and an estimated carbon cost to benefit ratio were also higher for plants inoculated with AM fungi from the Yuma orchard soil than for plants treated with inoculum from the other soils. The Yuma orchard inoculum was distinctive in that > 80% of the total number of AM fungal spores were from a single species, Glomus occultum. These data showed that root growth suppression of plants treated with the Yuma inoculum, compared with plants treated with inoculum from all other sites, was substantial and greater in magnitude than the effect of periodic soil drying. Suppression of root growth might have resulted from increased AM fungal activity resulting in higher carbon costs to the plant. (C) 2000 Elsevier Science B.V.
• Wright, G. C. (2000). Girdling 'Fairchild' Mandarins and 'Lisbon' Lemons to Improve Fruit Size. Citrus and Deciduous Fruit and Nut Research Report.
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  ‘Fairchild’ mandarins in the Phoenix area and ‘Lisbon’ lemons in Yuma were girdled beginning in November 1996. November, March and May girdling of the mandarins led to the greatest yield the first year, while March and May girdling led to the greatest yield in years 2 and 3. March girdling yield increases were generally due to greater fruit numbers, while in May, yield increases were due to greater fruit numbers and fruit size. Returns per acre suggest that March and or May girdling of mandarins will lead to greater profits for the grower. Like mandarins, lemon yields were greater following November, or November and March girdling after one year of the experiment. However, yields of these trees dropped considerably the second year, and the trees appear to be in an alternate bearing cycle. No lemon girdling treatment appears to be better than the untreated trees after three years.
• Wright, G. C., & Pena, M. A. (2000). Results of Scion and Rootstock Trials for Citrus in Arizona -- 1999. Citrus and Deciduous Fruit and Nut Research Report.
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  Five rootstocks, ‘Carrizo’ citrange, Citrus macrophylla, Rough lemon, Swingle citrumelo and Citrus volkameriana were selected for evaluation using 'Limoneira 8A Lisbon' as the scion. 1999-2000 results indicate that trees on C. macrophylla and C. volkameriana are superior to those on other rootstocks in both growth and yield. C. macrophylla is outperforming C. volkameriana. Rough lemon is intermediate, and ‘Swingle’ and Carrizo’ are performing poorly. In a similar trial, Four 'Lisbon' lemon selections, 'Frost Nucellar', 'Corona Foothills', 'Limoneira 8A' and 'Prior' were selected for evaluation on Citrus volkameriana rootstock. 1998-99 results indicate that the 'Limoneira 8A Lisbon' and ‘Corona Foothills Lisbon’ are superior in yield and fruit earliness. Results from another lemon cultivar trial suggest that ‘Cavers Lisbon’, Limonero Fino 49’ and “Villafranca’ lemons may be good candidates for plantings as well. Results from two other lemon scion trials, a navel orange cultivar trial and a ‘Valencia’ orange trial, and a mandarin trial are presented as well.
• Wright, G. C., & Pena, M. A. (2000). Use of a Slow Release Triazone-Based Nitrogen Fertilizer on Lemon Trees. Citrus and Deciduous Fruit and Nut Research Report.
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  Trisert CB replaced conventional foliar applied low-biuret urea and liquid urea ammonium nitrate in a typical N fertilization regime, a urea triazone based N source. There was no yield decrease, change in fruit size or grade with the use of the Trisert CB. There were no differences in leaf P, K, Ca, Mg, Cu, Fe, Mn or Zn concentration. Occasionally, leaf N concentration of trees supplied with foliar applied Trisert CB was higher than that of the control treatment.
• Mccloskey, W. B., & Wright, G. C. (1999). Applying roundup to the base of lemon tree canopies: effects on leaves, flowers, fruitlets, and yield. Citrus and Deciduous Fruit and Nut Research Report.
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  The effect of Roundup on lemon trees (Citrus limon) was evaluated by repeatedly spraying 0.5, 0.75, 1, 1.25, and 1.5 lb. a.i./acre (corresponding to 0.5, 0.75, 1, 1.25, 1.5 quarts of Roundup Ultra/acre) on the bottom 20 to 24 inches of the tree canopies, over a three year period. The Roundup applications caused significant leaf injury in the sprayed area of the canopies and there was also significant defoliation of branches at the higher Roundup rates in all three years of the study. In 1996 after three Roundup applications, increasing rates of Roundup had no effect on flower or fruitlet production in either the sprayed or unsprayed portions of the tree canopies as judged by the counts collected from branches in each canopy zone. Similarly, in 1997 after five Roundup applications, and in 1998 after nine Roundup applications, increasing rates of Roundup had no effect on flower or fruitlet production in the sprayed or unsprayed portions of the tree canopies. Spraying Roundup on the bottom of the tree canopies did not reduce total lemon yield per tree in 1996, 1997 or 1998 at any of the application rates. In all three years of the study, increasing Roundup rates had no effect on the yield of the first or second ring picks or the percentage of the total crop picked on the first harvest date. Increasing Roundup rates also did not affect fruit size at any harvest date in 1996, 1997 or 1998. Similarly, increasing Roundup application rates did not affect fruit quality at any harvest in 1996, 1997 or 1998. Thus, there was no relationship between the rate of Roundup sprayed on the trees and yield, fruit size or quality in all three years of this study. The three years of data collected in this study indicate that accidental drift or inadvertent application of Roundup onto lemon trees when spraying weeds on the orchard floor has no significant effect on lemon tree productivity.
• Mccloskey, W. B., & Wright, G. C. (1999). Evaluation and management of a "salina" strawberry clover cover crop in citrus: first year preliminary results. Citrus and Deciduous Fruit and Nut Research Report.
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  Two orchard floor management strategies were evaluated beginning in the fall of 1997 in a ‘Valencia’ orange (Citrus sinensis) grove at the University of Arizona Citrus Agricultural Center (CAC) in Waddell, Arizona. The clean culture or bare ground treatment produced more yield than the ‘Salina’ strawberry clover treatment when harvested on March 10, 1999 and the tree canopy volume of the clean culture treatment was also greater than that of the clover treatment. Yield efficiency (lbs of fruit per cubic meter of canopy) was similar in the two treatments. The clean culture treatment produced more large size fruit (size 88 and larger) and less small size fruit (size 113 and smaller) than the strawberry clover treatment. Although the yield efficiency parameter suggests that it may be possible to produce as much fruit in the clover treatment as the clean culture treatment, the total yield and fruit size distribution of the clover treatment compared to the clean culture treatment were characteristic of the negative effects of competition from vegetation on the orchard floor found in other studies. Based on previous studies, competition for water was the most likely cause of the negative competitive effect. Installation of additional tensiometers to measure soil moisture at greater depths and leaf water potential measurements to assess the degree of water stress in both treatments prior to irrigation will hopefully allow further improvement in irrigation scheduling to eliminate the negative affect of having vegetation on the orchard floor in the clover plots.
• Wright, G. C. (1999). 237 Rootstock and Scion Trials for Lemon in Arizona. Hortscience, 34(3), 483-483. doi:10.21273/hortsci.34.3.483a
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  Five rootstocks, `Carrizo' citrange, Citrus macrophylla, Rough lemon, `Swingle' citrumelo, and Citrus volkameriana, were selected for evaluation using `Limoneira 8A Lisbon' as the scion. Four years of yield and fruit packout data indicate that trees on C. volkameriana and C. macrophylla are superior to those on other rootstocks in growth and yield. `Swingle' and `Carrizo' are performing poorly, and Rough lemon is intermediate. In a similar trial, four `Lisbon' lemon selections, `Frost Nucellar', `Corona Foothills', `Limoneira 8A', and `Prior' selections of Lisbon lemon were selected for evaluation on Citrus volkameriana rootstock. Four years of yield and packout data indicate that the `Limoneira 8A Lisbon' selection has generally outperformed the other selections in both growth and yield, although `Corona Foothills' has been superior in the 1998-99 harvest season.
• Wright, G. C. (1999). The carbohydrate economy of horticultural crops: Introduction to the colloquium. HortScience, 34(6), 1014-1015.
• Wright, G. C., Tilt, P. A., & Pena, M. A. (1999). Results of scion and rootstock trials for citrus in Arizona - 1998. Citrus and Deciduous Fruit and Nut Research Report.
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  Five rootstocks, ‘Carrizo’ citrange, Citrus macrophylla, Rough lemon, Swingle citrumelo and Citrus volkameriana were selected for evaluation using 'Limoneira 8A Lisbon' as the scion. 1998-99 results indicate that trees on C. macrophylla and C. volkameriana are superior to those on other rootstocks in both growth and yield. C. macrophylla is beginning to outperform C. volkameriana. ‘Swingle’ and Carrizo’ are performing poorly. In a similar trial, Four 'Lisbon' lemon selections, 'Frost Nucellar', 'Corona Foothills', 'Limoneira 8A' and 'Prior' were selected for evaluation on Citrus volkameriana rootstock. 1998-99 results indicate that the 'Limoneira 8A Lisbon' selection is superior, and that ‘Corona Foothills Lisbon’ may also be superior to the other selections in both growth and yield. Results from another lemon cultivar trial suggest that ‘Cavers Lisbon’, Limonero Fino 49’ and “Villafranca’ lemons may be good candidates for plantings as well. Results from two other lemon scion trials, a navel orange cultivar trial and a ‘Valencia’ orange trial are presented as well.
• Matheron, M., Wright, G., & Porchas, M. (1998). Resistance to Phytophthora citrophthora and P. parasitica and nursery characteristics of several citrus rootstocks. Plant Disease, 82(11). doi:10.1094/PDIS.1998.82.11.1217
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  Studies were conducted to compare existing and potential citrus rootstocks with respect to resistance to root rot and gummosis caused by Phytophthora citrophthora and P. parasitica in greenhouse and growth chamber experiments and horticultural performance under simulated nursery conditions. Depending upon rootstock and experiment, mean root weights resulting from inoculation with P. citrophthora were 27 to 96% lower than the comparable controls. In similar experiments with the same rootstocks, inoculation with P. parasitica resulted in root weights that were 38 to 95% less than weights of the noninoculated controls. During 1994 or 1995, mean root weight reduction compared with noninoculated plants among Citrus macrophylla, rough lemon, C. volkameriana, and Sunki mandarin x Flying Dragon trifoliate (62-10919) attributable to P. citrophthora and mean root weight reduction among C. macrophylla, C. volkameriana, rough lemon, Sacaton citrumelo, Sunki mandarin x Flying Dragon trifoliate (62109-19), African shaddock x Rubidoux trifoliate, and Shekwasha mandarin x English trifoliate attributable to P. parasitica were significantly less than those recorded for all other tested rootstocks. Rootstocks that sustained a low percentage of root weight reduction generally experienced a low percentage of shoot weight reduction and survived longer as well. In evaluation of resistance to gummosis, depending on rootstock and experiment, the mean length of stem lesions caused by P. citrophthora on rootstocks ranged from 0.2 to 25.0 mm, whereas values for P. parasitica ranged from 0.2 to 18.5 mm. Stem lesions smaller than 5 mm in length were recorded for 21 and 14 of 36 different rootstocks inoculated with P. citrophthora and P. parasitica, respectively. On the other hand, P. citrophthora and P. parasitica caused stem lesions of at least 10 mm in length on 8 and 16 citrus rootstocks, respectively. Desirable nursery characteristics, including vigorous growth, minimal branching, and high leaf chlorophyll content, were demonstrated most prominently by Gomiri rough lemon, C. volkameriana, and Benton citrange, and to a lesser degree by some other rootstocks. Possible factors that could account for inconsistent classification of some citrus rootstocks as susceptible or resistant to Phytophthora root rot and gummosis are discussed.
• Mccloskey, W. B., & Wright, G. C. (1998). Applying Roundup to the Base of Lemon Tree Canopies: Preliminary Effects on Leaves, Flowers, Fruitlets, and Yield. Citrus and Deciduous Fruit and Nut Research Report.
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  The effect of Roundup on lemon trees was evaluated by repeatedly spraying 0.5, 0.75, 1, 1.25, and 1.5 lb. a.iJacre on the bottom 20 to 24 inches of the tree canopies over a three year period. The Roundup applications caused significant leaf injury in the sprayed area of the canopies and there was also significant defoliation of branches at the higher Roundup rates in all three years of the study. In 1996, flower and fruitlet counts were not affected by the Roundup applications and the 1998 data were inconclusive. However, flower and fruitlet counts in 1997 in the sprayed zone of the canopy were significantly reduced by Roundup and the effect increased with increasing Roundup rate. The 1996 and 1997 yield data indicated that Roundup applied to the bottom 20 to 24 inches of the tree canopies did not significantly affect lemon yield. The preliminary data suggest that accidental drift or misapplication of Roundup on to lemon trees when spraying weeds on the orchard floor has no short -term effect on grove productivity.
• Wright, G. C. (1998). Girdling Lemons to Improve Fruit Size and Set in Southern Arizona. Hortscience, 33(3), 499-499. doi:10.21273/hortsci.33.3.499a
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  Arizona lemon producers are often concerned with poor flowering, fruit set and fruit sizing, especially following excessively warm winter or spring weather. `Limoneira 8A Lisbon' (Citrus limon Burm.) lemons were girdled over a 3-year period to determine if girdling would improve yield or fruit size. Eight trees were girdled each month, from November through August, using a double spiral girdle and a 4.8-mm wide girdling knife. Fruit size measurements were taken throughout the growing season. Trees were harvested individually, and yield; fruit packout and fruit quality measurements were collected. For the 1995/96 harvest, trees girdled in March and May had greater early size and greater yields. Fruit quality was improved as well. For 1996/97 harvest year, trees girdled the previous November and December had significantly greater yield and fruit size. For trees harvested in 1997/98, no treatment was significantly better than the non-girdled trees. The effects of girdling on the orchard profitability will also be discussed.
• Wright, G. C. (1998). Growing Blackberries in the Low Desert. Citrus and Deciduous Fruit and Nut Research Report.
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  Berry plants should be well-watered when set out. If plants are irrigated with a hose or a bubbler head, water every three to seven days for the first two months, depending on temperature. When established, they can be watered in this way every one to two weeks. If drip or mini-sprinkler irrigation is used, apply one to two inches of water per week, irrigating every day when the plants are young, and every one to two days once the plants are established. Irrigate more frequently during dry, hot weather, when plants are flowering and when fruit is ripening.
• Mccloskey, W. B., & Wright, G. C. (1997). Preliminary Results Regarding the Effects of Foliar Applied Roundup on Lemon Physiology and Yield. Citrus Research Report.
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  The effect ofRoundup on lemon trees was evaluated by repeatedly spraying 0.5, 0.75, 1, 1.25, and 1.5 lb a.i/acre on the bottom 20 to 24 inches of the free canopies. Leaf injury symptoms, flower and fruit counts, and yield data were collected The Roundup applications caused significant leaf injury in the sprayed area of the canopies and there was significant defoliation of branches at the higher Roundup rates. In 1996, flower and fruitier counts were not affected by the Roundup applications. However, flower and fruitier counts in 1997 in the sprayed zone of the canopy were significantly reduced by Roundup and the effect increased with increasing Roundup rate. The 1996 yield data indicated that the Roundup applications did not significantly affect lemon yield, however, the effect of Roundup on the 1997 flower and fruitier counts suggests that there may be a yield effect in 1997. The preliminary data suggest that accidental drift of Roundup on to lemon trees when spraying weeds on the orchard floor has no short -term effect on grove productivity but this conclusion must be substantiated by further data collection. Introduction Weeds in Yuma Mesa lemon groves have been managed by frequent disking of the orchards and by the application of preemergence (i.e., soil applied) and postemergence (i.e., foliar applied) herbicides. Disking orchards occasionally damages tree branches and, in the opinion of some growers, may damage shallow tree roots. Disking also incorporates plant debris into the surface soil creating a breeding habitat for eye gnats on the Yuma Mesa. Thus, the use of herbicides has increased in recent years. Preemergence herbicides have not been widely used in Yuma County in the past because flood irrigation of sandy soils, especially on the Yuma Mesa, can leach some herbicides such as bromacil (e.g., Hyvar X and Krovar I), diuron (e.g., Karmex, Krovar I), and simazine (e.g., Princep) into the tree root zone causing injury. However, many preemergence herbicides including Goal, Prowl, Solicam, Surflan, Treflan, and Visor can be used on sandy soils without injuring trees. Postemergence herbicides are used to control weeds that escape the effects of preemergence herbicide applications or to control all weeds in groves that are not treated with preemergence herbicides. One of the most popular postemergence herbicides has been Roundup and occasionally some foliar injury symptoms caused by Roundup can be found on the skirts of trees. 'The authors wish to thank the Arizona Citrus Research Council and the Yuma County Pest Abatement District for partial financial support of this project. This is a progress report for project 95 -02 `Effects of Foliar Applied Roundup on Lemon Physiology and Yield'.
• Wright, G. C. (1997). Early Results of Scion and Rootstock Trials for Lemon in Arizona. Citrus Research Report.
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  Four 'Lisbon' lemon selections from the University of Arizona Citrus Budwood Certification plot were selected for evaluation on Citrus rootstock 'Frost Nucellar', 'Corona Foothills', 'Limoneira 8A' and 'Prior' were selected because of their popularity among Arizona growers or because of the lack of information about their performance under Arizona climactic and edaphic conditions. Trees were planted in 1993. Early results indicate that the 'Limoneira 8A Lisbon' selection is outperforming the other selections in both growth and yield. In a similar trial, five rootstocks were selected for evaluation using 'Limoneira 8A Lisbon' as the scion. Carrizo citrange, Citrus macrophylla, Rough lemon, Swingle citrumelo and Citrus volkameriana were chosen. Trees were planted in 1993. Early results indicate that trees on C. volkameriana are superior to those on other rootstocks in both growth and yield. Introduction There is no disputing the importance of lemon cultivars and rootstocks to desert citrus production. A successful lemon cultivar must be adaptable to the harsh climate, (where average high temperatures are often greater than 40 °C); must be vigorous and must produce high yields of good quality fruit of marketable size. Likewise, the ideal lemon rootstock must be compatible with the scion, be adaptable to the appropriate soil and climactic factors and should also improve one or more of the following characteristics: pest and disease resistance, cold tolerance, harvest date, internal and external fruit quality, I The author wishes to thank the Arizona Citrus Research Council for supporting this research. This is a combined final report for project 95 -16 Scion rootstock combinations for the Arizona citrus industry 1995, and project 96 -18 Lemon rootstock and cultivar breeding and evaluation for the Arizona citrus industry -1996. 11 yield and postharvest quality. Ultimately, the value of a rootstock for lemon lies in its ability to improve production and/or quality of the lemon fruit. Unfortunately, there is no one perfect lemon scion rootstock combination. Information as to the suitability of scions and rootstocks in non-desert areas of California is often not applicable to desert citrus growing areas. The Arizona citrus industry has suffered because of the shortfalls of certain scionrootstock combinations that were recommended for California but have shown themselves to be incompatible. Proper evaluation of both cultivar and rootstock in the desert is necessary before they are widely planted throughout the industry. Few Arizona lemon trials have been conducted, and data is old and/or incomplete. The most recent rootstock trial for lemons was using `Frost Nucellar Lisbon' lemon and was published by Rodney and Harris in 1976. This study indicated that greatest yield was for C. macrophylla, rough lemon, ` Rangpur' lime, `Troyer' citrange, and 'Carrizo' citrange. There were no trees planted on C. volkameriana, and there was no comparison of the effect of rootstock on fruit size or earliness Additionally, Fallahi et al. (1990) published some work comparing five `Lisbon' lemon cultivars with two `Eureka' varieties and 'Villafranca', all on C. macrophylla rootstock. `Prior Lisbon' had the greatest cumulative yield after 6 years, while the `Foothills Lisbon' had the largest fruit size. There has been no work on recent releases, such as `Limoneira 8A Lisbon'. Therefore, we have initiated two trials using scion and rootstock cultivars that are widely planted in the Arizona citrus industry today and using cultivars that are new. The lemon scion trial includes `Limoneira 8A Lisbon', `Prior Lisbon', `Frost Nucellar Lisbon', and `Corona Foothills Lisbon' lemon on C. volkameriana as the rootstock. A lemon rootstock trial is also underway This trial includes rough lemon (C. jambhiri), C. volkameriana, C. macrophylla, ` Carrizo' citrange and `Swingle' citrumelo as the rootstocks and `Limoneira 8A Lisbon' lemon as the scion. Data collected from these trials includes tree growth, mineral nutrition, fruit quality, fruit size and total yield Materials and Methods These experiments were established in March 1993 in Block 26 of the Yuma Mesa Agricultural Center, near Yuma, Arizona. The land was laser leveled and fumigated prior to planting. Trees were planted on a 10 m x 10 m spacing. Ten replicates of each of the 5 rootstocks were planted, and 12 replicates of each of the 4 scions were planted, for a total of 98 trees. Experimental design is randomized complete block. Irrigation is border flood, and normal cultural practices are used. Growth data, expressed as trunk diameter, is taken annually in March. Measurements are taken about 5 cm inches below the scionrootstock interface (bud union), and about 10 cm above. These locations are permanently marked with paint. Diameters were taken of both the scion and rootstock, during 1994 and 1995 so as to quantify and differential growth rates that might have occurred. These differences were less apparent during 1996, so only scion trunk diameter data was collected. Leaves are collected annually in August for mineral analysis, however there have been no significant differences. Fruit diameter data was collected semiweekly in 1995 and 1996. One fruit of a representative size per tree was tagged, and was measured until harvest. Replacement fruits of approximately the same size were selected if a fruit was harvested or if it abscised. Yield data is collected during the fall and winter. Trees are ring or strip picked as noted below. Cull fruits are then removed, and the remaining fruits are then sized, and reported as the number of fruit in a typical 17.2 kg box. Fruit quality data was collected at each harvest time. These data include °brix, peel thickness, percentage juice, pH, and total soluble solids to total acid ratio. Data was analyzed using SPSS for Windows (SPSS Inc., Chicago, Illinois).
• Karim, M. R., Taylor, K. C., & Wright, G. C. (1996). Effect of Foliar Boron on Fruit Yield and Quality of Citrus sinensis cv. Hamlin. Hortscience, 31(4), 671-671. doi:10.21273/hortsci.31.4.671d
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  A field trial conducted at Yuma, Ariz., examined the effect of foliar boron application on fruit yield and quality of Citrus sinensis cv. Hamlin. Boron was applied to 5-year-old trees at five treatment levels (0, 500, 1000, 2000, and 3000 ppm) before or after flowering in a split plot design. At harvest, fruit number, size and quality were determined. Yield (P = 0.01) and average fruit number per tree (P = 0.02) were different among treatments. The highest yield was obtained with the 500 ppm treatment. In this first year of the trial there was no difference in average fruit weight, fruit pH, titratable acidity, peel thickness, juice volume, or soluble solid content of fruit between the treatments. Previous studies indicate that boron influenced in vivo and in vitro pollen germination in many crops. Increased fruit yield may have occurred because boron was transported to the flowers where it exerted its influence on increased fruit set through an effect on pollen viability or pollen tube growth. Further investigation of this hypothesis is underway.
• Karim, M. R., Wright, G. C., & Taylor, K. C. (1996). Effect of Foliar Boron Sprays on Yield and Fruit Quality of Citrus. Citrus Research Report.
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  Deficiency of boron (B) in citrus has serious consequences for tree health and crop production. There is evidence that B deficiency may be a problem in Arizona citrus. Certainly, many symptoms of B deficiency are apparent, especially on the Yuma Mesa. A field trial was conducted at Yuma, Arizona to examine the effect of foliar boron application on fruit yield and quality of Citrus sinensis and C. limon. Boron was applied to 5 year old Citrus sinensis cv. Hamlin and C. limon cv. Rosenberger Lisbon trees at 5 different concentrations (0 ppm, 500 ppm, 1000 ppm, 2000 ppm, 3000 ppm) either before flowering or after flowering. At harvest, fruit yield and quality, and boron concentrations were determined. Foliar application appeared to increase leaf boron concentration (r= 0.50, p= 0.004). Fruit set was increased in Hamlin trees receiving bloom and post bloom applications of boron at the 1000 ppm level. Boron applications had no significant effect on lemon yield in these studies. This fruit set increase in Hamlin accounted for a 35% increase in overall yield relative to control trees. However, there was no significant difference in fruit weight, fruit pH, titratable acidity, peel thickness, juice volume, or soluble solid content of the fruits among treatments. Previous studies indicate that boron influenced in vivo and in vitro pollen germination in many crops. A plausible explanation for increased fruit yield may be that the applied boron was transported to the flowers where it exerted its influence of increased fruit set through an effect on pollen viability and/or pollen tube growth. However, clearly boron supplementation must be performed judiciously to avoid fruit drop from over -application of the element.
• Mccloskey, W. B., Wright, G. C., & Taylor, K. C. (1996). Managing Vegetation on the Orchard Floor in Flood Irrigated Arizona Citrus Groves. Citrus Research Report.
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  Several orchard floor management strategies were evaluated beginning in the fall of 1993 in experiments on the Yuma Mesa in a Limoneira 8A Lisbon lemon grove and in a Valencia orange grove at the University of Arizona Citrus Agricultural Center (CAC) in Waddell, Arizona . On the Yuma Mesa, disking provided satisfactory weed control except underneath the tree canopies where bermudagrass, purple nutsedge, and other weed species survived. Mowing the orchard floor suppressed broadleaf weed species allowing the spread of grasses, primarily bermudagrass. Preemergence (Solicam and Surflan) and postemergence (Roundup and Torpedo) herbicides were used to control weeds in the clean culture treatment in Yuma. After two harvest seasons (1994 -95 and 1995 -96), the clean culture treatment resulted in greater yield than the other treatments. At the CAC, clean culture (in this location no preemergence herbicides were used), mowed resident weeds, and Salina strawberry clover orchard floor management schemes were compared. Again the clean culture treatment yielded more than the mowed resident weeds. The yield of the strawberry clover treatment was somewhat less than the clean culture yield but not significantly less. The presence of cover crops or weeds on the orchard floor were found to modulate tree canopy temperatures, and to have beneficial effects on soil nitrogen and soil organic matter content, but no effect on citrus leaf nutrient content. The decrease in yield in the mowed resident weed treatments compared to the clean culture treatment in both locations was attributed to competition for water.
• Wright, G. C., Taylor, K. C., & Mccloskey, W. B. (1996). A Comparison of Four Orchard Floor Management Strategies for Lemons in Southwestern Arizona. Hortscience, 31(4), 578-578. doi:10.21273/hortsci.31.4.578b
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  Four orchard floor management strategies—disking, mowing, chemical mow, and clean culture using herbicides—were evaluated in a `Limoneira 8A Lisbon' lemon orchard in Southern Arizona, starting in the fall of 1993. Disking was the cultural practice used to manage the orchard floor before the start of the experiment. Although disking the orchard floor may have injured shallow tree roots, it provided satisfactory weed control except underneath the tree canopies where bermudagrass, purple nutsedge, and other weed species survived. Chemical mowing with Roundup at 1.168 L/ha did not provide satisfactory control of many weed species and required too many applications to be commercially feasible. This treatment was converted to a combination clean culture and disk treatment (clean and disk) in Summer 1995. Mowing the orchard suppressed broadleaf weed species, allowing the spread and establishment of grasses, primarily bermudagrass, and to a lesser extent, southern sandburr. A fall application of Solicam and Surflan followed by a summer spot treatment application of Roundup was used to control the weed flora in the clean culture treatment. Spot treatment applications of sethoxydim (Poast and Torpedo) were also made to control bermudagrass growing under the tree canopies in the clean culture treatment. Total 1995 yield of the mow, clean & disk, disk, and clean culture treatments were 4867, 5112, 5216, and 6042 kg of fruit, respectively. For the first harvest of 1995, the trees under clean culture also had significantly greater numbers of large fruit than did the trees under the other treatments.
• Brown, P., Sanchez, C. A., Wilcox, W., Wilcox, M., Wright, G. C., & Wright, G. C. (1995). Response of `Lisbon' Lemons to Irrigation Frequency in the Arizona Desert. Hortscience, 30(4), 839-839. doi:10.21273/hortsci.30.4.839b
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  The majority of citrus planted in southwestern Arizona are lemons. Lemons are generally more vigorous and usually produce higher yields than other citrus cultivars. However, under water stress, fruit size will be compromised and excessive fruit drop will occur. Limited information is available that addresses the issue of irrigation frequencies and the impact on fruit sizing of lemons. A field study was initiated in 1993 evaluate the response of `'Lisbon' lemons to various flood irrigation intervals. Irrigation intervals were based on soil moisture depletion (SMD), as calculated from frequent neutron probe soil moisture measurements. Individual treatments were irrigated when total SMD was 25%, 40%, 55%, and 70%, respectively. The experiment is a completely random design with four replications. Results indicate that both the most-frequent (25% SMD) and least-frequent (70% SMD) irrigation regimes produced negative results. Overall, the first year's results indicate optimal fruit growth and yield is achieved at 40% SMD.
• Tilt, P. A., Wilcox, M. A., & Wright, G. C. (1995). Selective Pruning of Young Lemon Trees to Increase Fruit Size. Hortscience, 30(4), 844-844. doi:10.21273/hortsci.30.4.844a
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  Growth of young lemon trees (Citrus limon Burm. f.) is extremely vigorous, and is characterized by the appearance of highly vigorous upright shoots that originate in the scaffold branches and trunk of the tree. While maturing, these shoots are considered to be in competition for photosynthates with smaller fruit in the spring and with mature fruit in the fall. During 1993 and 1994, we selectively removed these shoots 12, 6, 4, and 1 (1994 only) times per year, with the objective of increasing fruit size. Neither yield nor fruit quality was affected by the pruning treatments during 1993, but pruning trees 12 times per year increased fruit size by 30% compared to unpruned trees. In 1994, lemon trees pruned 4 times per year had 50% less cull fruit than unpruned trees, and 22% more fruit of size 140 or larger. However, >99% of the flowers and small fruit on trees pruned 4 times per year were aborted, compared with 95% abortion on the unpruned trees. Trees pruned 4 times per year also had 40% less yield compared with those that were unpruned.
• Wright, G. C., Patten, K. D., & Drew, M. C. (1995). Labeled sodium (22Na+) uptake and translocation in rabbiteye blueberry exposed to sodium chloride and supplemental calcium. Journal of the American Society for Horticultural Science, 120(2), 177-182.
• Wright, G. C., Patten, K. D., & Drew, M. C. (1994). Mineral composition of young rabbiteye and southern highbush blueberry exposed to salinity and supplemental calcium. Journal of the American Society for Horticultural Science, 119(2), 229-236.
• Drew, M. C., Patten, K. D., & Wright, G. C. (1993). GAS EXCHANGE AND CHLOROPHYLL CONTENT OF 'TIFBLUE' RABBITEYE AND 'SHARPBLUE' SOUTHERN HIGHBUSH BLUEBERRY EXPOSED TO SALINITY AND SUPPLEMENTAL CALCIUM. Journal of the American Society for Horticultural Science, 118(4), 456-463. doi:10.21273/jashs.118.4.456
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  `Tifblue' rabbiteye blueberry (Vaccinium ashei Reade) and `Sharpblue' southern highbush blueberry (primarily V. corymbosum) were treated with 0, 25, or 100 Mm Na+ as Na2SO4 or NaC1, and 0, 1, 3, or 10 Mm supplemental Ca2+ in sand culture in the greenhouse. Greatest stomatal conductance (gs) and net assimilation (A) occurred in unsalinized `Tifblue' plants not given additional Ca2+. Stomatal conductance, A, transpiration (E), and xylem water potential(Ψ)of `Tifblue' and `Sharpblue' plants were all lowered as salinity increased, and these effects were more pronounced with NaCl than with Na2SO4. After 63 days, for plants given 100 Mm Na+ as NaCl, gs and net assimilation rate were reduced to only 10% of the unsalinized controls, while for plants salinized with 100 mm Na+ as Na2SO4, gs and A were 35% and 43%, respectively, of unsalinized controls. Leaf necrosis was more extensive on `Sharpblue' plants given NaCl than on `Tifblue' plants. Neither Ca2+ nor Na+ treatments led to severe chlorosis; reductions in leaf chlorophyll content were mainly due to necrosis. The Na+- induced reduction in gas exchange was associated with negative Ψw Ca2+ deficiency, or a combination of these factors. Additional factors leading to inhibition of gas exchange in NaCl- stressed plants include Cl- toxicity and leaf necrosis. Calcium supplements were unable to ameliorate NaCl damage in `Tifblue' or `Sharpblue' plants, possibly because of the inability of Ca2+ to counter Cl- entry and toxicity. In contrast, additional Ca2+ improved gs, A, Ψw, and leaf chlorophyll content of `Tifblue' plants that received Na2SO4. For plants treated with 25 mm Na+ as Na2SO4 and 1 mm Ca2+, gs was 1.5 to 2.5 times higher than in plants without added Ca2+. Low (1 mm) concentrations of Ca2+ were more effective in ameliorating the effects of 100 mm Na+ as Na2SO4. than were 3 or 10 mm Ca2+ supplements, possibly because higher Ca2+ concentrations damaged the metabolism of the calcifuge blueberry.
• Drew, M. C., Patten, K. D., & Wright, G. C. (1992). SALINITY AND SUPPLEMENTAL CALCIUM INFLUENCE GROWTH OF RABBITEYE AND SOUTHERN HIGHBUSH BLUEBERRY. Journal of the American Society for Horticultural Science, 117(5), 749-756. doi:10.21273/jashs.117.5.749
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  ‘Tifblue’ and ‘Brightwell’ rabbiteye blueberries (Vaccinium ashei Reade.) were subjected to 0, 25, or 100 mM Na, as Na2SO 4 or NaCl, and 0, 1, 3, or 10 mM supplemental Ca 2+ , primarily as CaSO4, in an irrigated sand culture in the greenhouse. Additionally, the effect of NaCl on ‘Sharpblue’ southern highbush blueberry (primarily V. corymbosum L.) was examined. For unsalinized plants, fastest growth occurred in plants not receiving supplemental Ca. Root and shoot growth were depressed as salinity increased in plants lacking additional Ca . With 100 mM Na as Na2SO4. ‘Tifblue’ root and shoot dry weight increases were only 37% and 25%, respectively, of the increase of unsalinized controls, while with 100 mM Na as NaCl, the corresponding shoot and root dry weight increases were only 38% and 43%, respectively. ‘Brightwell’ plants reacted similarly to ‘Tifblue’ in salinity treatments with Na 2SO4 and NaCl, but ‘Sharpblue’ plants were more severely affected by 100 mM NaCl than were the rabbiteye cultivars. In no case did addition of Ca have any ameliorative effect on either the dry weight of roots of plants exposed to 25 or 100 mM NaCl or on the shoot growth of plants exposed to NaCl. The inability of Ca 2+ to counter Clentry or toxicity may account for the lack of amelioration. In contrast, additional Ca 2+ did improve shoot growth of plants exposed to Na2SO4. For ‘Tifblue’ plants supplied with 25 mM Na + as Na2SO4, growth increased by almost 25% in the presence of 10 mM Ca, while for ‘Tifblue’ plants treated with 100 mM Na as Na2SO4, growth was more than three times greater in plants supplied with 1 mM Ca than in those not given any Ca. Growth increase was primarily due to increased leaf area and number. Low (1 mM) concentrations of Ca were more effective in ameliorating the effects of 100 mM Na as Na2SO4 than were 3and 10-mM Ca 2+ supplements, possibly because higher Ca additions lead to metabolic damage in these calcifuge Vaccinium species. Rabbiteye and southern highbush blueberries require good quality water to thrive and produce well. Many regions of the southeastern United States lack sufficient good quality water throughout the growing season. Saline ground water has emerged as a major difficulty limiting the expansion of the industry. Water pH < 7.0, total Na < 2.0 mM, total HCO3 –
• Drew, M. C., Patten, K. D., & Wright, G. C. (1990). INFLUENCE OF SUPPLEMENTAL CA2+ ON UPTAKE AND TRANSLOCATION OF 22NA+ IN RABBITEYE BLUEBERRY. Hortscience, 25(9), 1148-1148. doi:10.21273/hortsci.25.9.1148e
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  Blueberry reducers in Texas must often irrigate with sodic water. Excess Na+ leads to reduced growth, necrosis, and plant mortality. Ca2+ is known to ameliorate such detrimental effects in many crops, but little is known about the response of rabbiteye blueberry. To elucidate the influence of Ca2+ on the uptake and translocation of Na+, plants were subjected to NaCl in hydroponics solutions (10, 25, 50 and 100 mM NaCl) and the uptake of Na+ was traced over a 24h period using 22Na+ Additionally, for each treatment, half the plants were supplied with 10 mM Ca2+. Plants were then transferred to identical, but unlabeled, solution, then harvested at intervals up to 28 days following cessation of labelling.Preliminary results indicate that plants subjected to 25 mM Na+ and 0 mM Ca2+ showed less ability to exclude Na+ from the roots, and accumulated more Na+ in roots, stems, an leaves than did plants supplied with 25 mM Na+ and 10 mM Ca2+. Leaf tissue accumulated more Na per gram fresh weight than did any other part of the plant, regardless of Ca2+ treatment.Results from the remaining treatments, root 22Na+ efflux data, and total tissue Na+ and Ca2+ concentrations will also be reported.
• Harris, M. K., Sprinz, P. T., Storey, J. B., & Wright, G. C. (1990). Pre-harvest Pecan Yield Estimation. Hortscience, 25(6), 698-700. doi:10.21273/hortsci.25.6.698
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  Nut count (NC), trunk circumference (TC), competition factor (CF), days from budbreak (DAY), and high or low crop year (YR) data were collected on 40 trees at three sites across Texas in 1985 and 1986, to create a model that would predict pecan yield. The model developed predicted the natural logarithm of the total nuts on the tree (...). The equation accounts for 87% of the variation in yield. The model is not sufficiently accurate to predict individual tree yields well, but additional data show an ability to accurately predict average tree yields

Proceedings Publications

• Wright, G. C. (2018, March). The Date Industry in the United States and Mexico. In Sixth International Date Palm Conference, 117-122.
• Wright, G., & Kahn, T. (2012, Fall). Evaluation of Lemon Selections for the deserts of the United States. In Proc. Intl. Citrus Congress, 312.

Presentations

• Hu, J., & Wright, G. C. (2025, August).

  Monitoring Sporal Disposal and Infections  of Fomitopsis meliae Using Spore Traps and a New qPCR Method

  . Plant Health 2025. Honolulu, HI: American Phytopathological Society.
• Wright, G. C. (2018, March). The Date Industry in the United States and Mexico. Sixth International Date Palm Conference. Abu Dhabi, United Arab Emirates.
• Wright, G. C., & Schuch, U. K. (2015, October). Pomegranates - The Arizona Story. Florida Pomegranate Society Conference. Lake Alfred, FL: Florida Pomegranate Society.
• Wright, G. C. (2014, February). Manejo de huertos de mandarinas en ambientes desérticos. Citrica 2014, Lima Peru. Lima, Peru: Informaccion/Lima -Peru and UNALM - Universidad Nacional Agraria La Molina / Lima - Perú.
• Wright, G. C., Johnson, D., & El Houmaizi, M. A. (2014, March). Medjool- the King of Dates, and elite date cultivar. Fifth International Date Palm Congress, Abu Dhabi. Abu Dhabi, United Arab Emirates: UAE University.

Poster Presentations

• Federici, C., Thomas, Z., Seymour, D., Wright, G. C., & Roose, M. (2024, October 2024). Rootstock trials for lemon in California. California Citrus Conference. Visalia, CA: California Citrus Research Board.
• Hu, J., & Wright, G. C. (2024, November/Fall). Isolation and characterization of novel Trichoderma strains with antagonistic activities against Fomitopsis meliae. . The XV International Citrus CongressThe XV International Citrus Congress.
• Kahn, T., Siebert-Wooldridge, T., Trunelle, K., Federici, C., Thomas, Z., Seymour, D., Wright, G. C., & Roose, M. (2024). UCR Breeding Program Develops New Scion Selections. California Citrus Conference.
• Wright, G. C., & Hu, J. (2024, November/Fall). Incidence and Control of Brown Wood Rot in Arizona and California Desert Lemon Trees. The XV International Citrus CongressThe XV International Citrus Congress.
• Piscatella, R., Thomas, Z., Wright, G. C., Kahn, T., Siebert-Wooldridge, T., Trunell, K., Federici, C. T., Roose, M., & Seymour, D. (2021, October). Leveraging Drones for Future Data Collection from Field Trials. California Citrus Conference. Visalia, CA: California Citrus Research Board.
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  The manual collection of phenotypic data from field trials is physically demanding, time consuming, and expensive. Individuals must traverse field trials armed with measuring tapes, rulers, and their best judgment to measure and record data points by hand. Depending on the size of the field, these efforts often require multiple workers for hours if not days of labor. Manual measurements of tree performance are also prone to experimenter bias, especially for qualitative traits like scores of tree health. The emergence of camera-fitted drones allows us to automate this intensive process to reduce both time and resources required for data collection. First, we compare manual measurements of tree size to those captured by drones. We have collected both sets of data for two lemon field trials located in Riverside and Santa Paula, California. Automated measurements are highly correlated with manual measurements of tree and canopy size. Further testing and analysis will be performed to ensure that automated phenotyping using drones is a reliable substitute for manual measurements of tree size in field trials.
• Wright, G. C., Kahn, T., & Roose, M. (2021, October). Current Yield, Packout and Fruit Quality Results from Multilocation Lemon Scion Trials in California. California Citrus Conference. Visalia, CA: California Citrus Research Board.
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  We established multilocation (ML) lemon scion trials at four sites in Spring 2015. These locations include the LREC, a Limoneira-owned block near Santa Paula (SP), the UCR Agricultural Experiment Station (UCR), and the Coachella Valley Agricultural Research Station (CVARS), near Thermal. At each location, we planted 18 trees each of ‘Limoneira 8A Lisbon’ (L8A), ‘Limoneira 8A-IR1’ (IR1 - a low-seeded irradiated selection of ‘Limoneira 8A’), ‘Corona Foothills’(CFH), ‘Limonero Fino 49’(F49), ‘Walker Lisbon’ (WLK), and ‘Yen Ben’(YBN). Trees were budded to three rootstocks which varied by location. Yield data from LREC indicates that WLK has performed the best so far, while at SP, WLK and L8A have performed the best. At UCR, CFH, F49, L8A and WLK have performed well, while at CVARS, CFH and F49 are the best performers. Performance of IR1 varies depending on site and rootstock, while YBN performs poorly at all locations. There are scion by rootstock interactions at each site, but the best performers have cumulative yields of between 400 to 800 lbs. per tree regardless of site. CFH, F49 and occasionally IR1 typically have the largest fruit size, followed by L8A. and WLK. YBN has the smallest fruit. Again, there are interactions between scion and rootstock affecting fruit size at each site. Both IR1 and YBN have significantly fewer seeds than the other selections. Research supported by CRB project 5200-201
• Hoddle, M., & Wright, G. C. (2018, March). The South American Palm Weevil. Sixth International Date Palm Conference. Abu Dhabi, United Arab Emirates.
• Wright, G. C. (2017, August). Application of plant growth regulators and calcium to reduce skin separation in ‘Medjool’ dates. XIII International Symposium on Plant Bioregulators in Fruit Production. Chiba, Japan: International Society for Horticultural Science.
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  Summary: ‘Medjool’ is one of the world’s most expensive and profitable dates. However, costs to grow the fruit are also high, so the highest quality must be maintained. Exterior appearance is an important quality parameter. Skin separation (Figs. 1 and 2) is a defect that can downgrade the fruit and reduce profits. Skin separation occurs when the epicarp separates from the mesocarp; a phenomenon that appears only once the fruit dries to the rutab to the tamar stage, not in the khalal (colored) stage. Calcium, GA, and ABA have all been proposed to reduce skin separation. Applications of CaCl2(625 mg/l), S-ABA (500 ppm), CaCl2 (625 mg/l) + S-ABA (500 ppm), ProGibb® 40% at 24 g a.i., ProGibb® 40% at 32 g a.i., CalTrac (Ca fertilizer mfg. by Yara North America) at 4.7 l/ha and Powerbor CA (Calcium-boron fertilizer mfg. by Yara North America) at 4.7 l/ha were made to individual bunches of date fruit on 20 trees in two orchards in late July 2016. Two sequential harvests for each orchard occurred in September 2016, then the fruit was sorted by color, dehydrated to a uniform moisture content and resorted for quality. There was no consistent effect of treatments upon fruit color in the first harvests. However, applications of ProGibb led to significantly more fruit in the yellow khalal stage for the second harvests in both orchards. Applications of ABA, and sometimes ABA + CaCl2 led to a 5 to 10% increase in fruit of the higher quality, but these increases were trends, and were not significant. Subsequent experiments should take application timing into consideration.
• Wright, G. C., & Kahn, T. L. (2016, September). LEMON CULTIVAR EVALUATION FOR THE CALIFORNIA AND ARIZONA DESERTS. International Society of Citriculture Conference. Foz do Iguassu, Brazil: International Society of Citriculture.
• Wright, G. C., Matheron, M. E., & Martin, P. (2016, September). ANTRODIA SINUOSA – A WOOD ROTTING FUNGUS THAT ADVERSELY AFFECTS LEMONS IN ARIZONA. International Society of Citriculture Conference. Foz do Iguassu, Brazil: International Society of Citriculture.
• Wright, G. C., & Schuch, U. K. (2015, Aug). Pomegranate Variety Trial in Arizona. American Society for Horticultural Sciences Conference. New Orleans: American Society for Horticultural Sciences.
• Schuch, U. K., Wright, G. C., & Mahato, T. (2014, May 9). Pomegranate Variety Trial in Southern Arizona. Desert Horticulture Conference, Tucson. Tucson.
• Schuch, U. K., Wright, G. C., & Mahato, T. (2014, November 10). Pomegranate Variety Trial in Southern Arizona. CALS Annual Research Poster Forum, Tucson. Tucson.
• Wright, G. C. (2014, August). Mechanization and Innovation In The High-Value ‘Medjool’ Date Palm Orchard - Moving Into The Future. International Horticultural Congress, Brisbane. Brisbane, Australia: International Society for Horticultural Sciences.
• Wright, G. C., & Kahn, T. L. (2014, August). Evaluation of 12 Lemon Selections in The California Desert. International Horticultural Congress, Brisbane. Brisbane, Australia: International Society for Horticultural Sciences.
• Schuch, U. K., Wright, G. C., & Mahato, T. (2013, July). Pomegranate Variety Trial in Southern Arizona.. ASHS Annual Conference. Palm Desert, CA: American Society for Horticultural Sciences.

Others

• Wright, G. C., & Hu, J. (2025, May).

  Arizona Homeowner Guide to Citrus Greening Disease

  . University of Arizona Cooperative Extension Publication AZ2132. https://www.extension.arizona.edu/sites/default/files/2025-05/az2132_Arizona-Homeowner-Guide-to-Citrus-Greening-Disease.pdf
• Begeman, J., & Wright, G. C. (2024, February). Diagnosticando problemas de los cítricos de casa. Arizona Cooperative Extension Publication AZ1492S-2024.
  More info

  https://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/az1492S-2024.pdf
• Wright, G. C. (2024, June). Citrus Rootstock Acquisition and Evaluation – 2023. Arizona Citrus Research Council Website. https://agriculture.az.gov/arizona-citrus-research-council-previously-funded-research-projects
• Wright, G. C. (2024, June). Field Trials to Reduce Brown Wood Rot – 2023-24 . Arizona Citrus Research Council Website. . https://agriculture.az.gov/arizona-citrus-research-council-previously-funded-research-projects
• Wright, G. C. (2023, June). Citrus Rootstock Acquisition and Evaluation – 2022-23. Arizona Citrus Research Council Website. https://agriculture.az.gov/arizona-citrus-research-council-previously-funded-research-projects
• Wright, G. C. (2023, June). Field Trials to Reduce Brown Wood Rot – 2022-23 . Arizona Citrus Research Council Website. . https://agriculture.az.gov/arizona-citrus-research-council-previously-funded-research-projects
• Wright, G. C. (2022, June). Citrus Rootstock Acquisition and Evaluation – 2020-21. Arizona Citrus Research Council Website. https://agriculture.az.gov/arizona-citrus-research-council-previously-funded-research-projects
• Wright, G. C. (2022, June). Tabla de fertilización de cítricos en Arizona. Arizona Cooperative Extension Publication AZ1671S-2022. https://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/az1671S-2022.pdf
• Wright, G. C. (2021, June). Grapefruit and Pummelo for Southern Arizona. Arizona Cooperative Extension Publication AZ1925-2021. https://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/az1925-2021.pdf
• Wright, G. C. (2021, May). Citrus Rootstock Acquisition and Evaluation - 2019. Arizona Citrus Research Council Website. https://agriculture.az.gov/arizona-citrus-research-council-previously-funded-research-projects
• Wright, G. C. (2021, May). Irrigating Citrus Trees. Arizona Cooperative Extension Publication AZ1151-2021. https://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/az1151-2021.pdf
• Wright, G. C. (2020, JUly). Cómo regar los cítricos. Arizona Cooperative Extension Publication AZ1151S-2020. https://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/az1151S-2020.pdf
• Wright, G. C. (2020, September). Oranges for Southern Arizona. Arizona Cooperative Extension Publication AZ1850-2020. https://extension.arizona.edu/pubs/oranges-southern-arizona
• Hu, J., & Wright, G. C. (2019, July). Coupling Spore Traps and Quantitative PCR Assays for Detection and Quantification of Airborne Spores of Antrodia sinuosa in Lemon Orchards of Yuma - 2018. Arizona Citrus Research Council Website https://agriculture.az.gov/arizona-citrus-research-council-previously-funded-research-projects. https://agriculture.az.gov/sites/default/files/documents/Coupling%20Spore%20Traps%20and%20Quantitative%20PCR%20Assays%20for%20Detection%20and%20Quantification%20of.......%20-%202018.pdf
• Hu, J., & Wright, G. C. (2019, June). Huanglongbing of Citrus. University of Arizona Cooperative Extension Publication AZ 1795. https://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/az1795-2019.pdf
• Wright, G. C., & Poe, S. E. (2019, July). Citrus Rootstock Acquisition and Evaluation — 2018. Arizona Citrus Research Council Website https://agriculture.az.gov/arizona-citrus-research-council-previously-funded-research-projects. https://agriculture.az.gov/sites/default/files/documents/Citrus%20Rootstock%20Acquisition%20and%20Evaluation%20%20-%202018.pdf
• Wright, G. C. (2018, March). Control of Brown Wood Rot in Lemons - 2017. Arizona Citrus Research Council Website.
  More info

  file:///C:/Users/Glenn%20Wright/Downloads/Control%20of%20brown%20wood%20rot%20in%20lemons%20-%202017.pdf
• Wright, G. C., & Poe, S. E. (2018, March). Citrus Rootstock Acquisition and Evaluation — 2017. Arizona Citrus Research Council Website.
  More info

  file:///C:/Users/Glenn%20Wright/Downloads/Citrus%20Rootstock%20Acquisition%20and%20Evaluation%20New%20%20%202017.pdf
• Wright, G. C. (2015, February). Area-Wide Spraying for Asian Citrus Psyllid in Texas and Florida. Commodity Research Report. http://extension.arizona.edu/pubs/area-wide-spraying-asian-citrus-psyllid-texas-and-florida
  More info

  Realizing that the Arizona citrus industry might someday have to deal with widespread ACP control, the Arizona Citrus Research Council approved a trip to Florida and Texas to investigate how ACP control was accomplished in those two states. The trips were to McAllen, Texas on 9-12 Nov 2011 and to Immokalee Florida on 17-18 Nov. 2011. In McAllen, I interviewed Dr. Mamoudou Setamou, extension entomologist for Texas A&M – Kingsville and his staff, and Mr. Ray Prewitt, president of Texas Citrus Mutual. In Florida, I interviewed Mr. Ron Hamel, manager of the Gulf Citrus Growers, and Dr. Mongi Zekri, southwest Florida Multi-County Citrus Agent, housed at the Hendry County Extension Office in LaBelle., FL. The author hopes that some of this information can be used in the development of an Area Wide Spray Plan in Arizona.
• Wright, G. C. (2015, February). Control of Brown Wood Rot in Lemons with Low Pressure Injection 2012. Commodity Research Report. http://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/az1652-2015.pdf
  More info

  Abstract We injected AGRA PHOS (Potassium Phosphite) 0-2.4-2, Propaconizole – 0.05%, Propaconizole plus Azoxystrobin – 0.117 and 0.135% respectively, Zn, Mn and Fe 0.105, 0.112, and 0.10% respectively, and Azoxystrobin – 0.137% using a low pressure injection system for the control of Antrodia sinuosa in lemon trees. The Propaconizole + Azoxystrobin treatment, the Azoxystrobin treatment, and the Zn + Mn + Fe treatment led to significantly less fungal lesion growth when applied prior to the introduction of the fungus, as compared to their application after fungal introduction.
• Wright, G. C. (2015, February). Evaluation of Nitrogen Fertilization Practices for Surface-Irrigated Lemon Trees – 2012. Commodity Research Report. http://extension.arizona.edu/pubs/evaluation-nitrogen-fertilization-practices-surface-irrigated-lemon-trees-2012
  More info

  Abstract: Lisbon lemons were treated with N levels ranging from 0.5 to 3.0 lbs. N per tree annually. Fourth–season yield results from the trial show significant effects of the treatments upon overall yield and leaf N concentrations, but no effect upon fruit packout. Treatments did lead to a significant effect upon leaf nutrient concentration. Total cumulative yields from 2008 to 2012 (not including the freeze-affected 2011-12 season) were significantly affected by the treatments. Trees treated annually with 2.0 lbs N had the greatest yield, which represented a 12% increase over the yield of trees treated with just 0.5 lbs. N annually.
• Wright, G. C. (2015, July). Citrus Fertilization Chart for Arizona. CALS Extension Publication #AZ1671. http://extension.arizona.edu/pubs/citrus-fertilization-chart-arizona
• Wright, G. C. (2015, September). Control of Brown Wood Rot in Lemons with Low Pressure Injection 2013-14. Commodity Research Report. http://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/az1680-2015.pdf