Editing Citrus (section)

== Cultivation ==

{{Further|Citrus production}}

[[File:Mandariner Citrus deliciosa.jpg|thumb|Mediterranean Mandarin (''[[Citrus × deliciosa]]'') plantation, [[Mallorca]] ]]

Most commercial citrus cultivation uses trees produced by [[grafting]] the desired fruiting [[cultivar]]s onto [[citrus rootstock|rootstocks]] selected for disease resistance and hardiness.<ref name="RHS growing guide">{{cite web |title=How to grow citrus fruit |url=https://www.rhs.org.uk/fruit/citrus/grow-your-own |publisher=[[Royal Horticultural Society]] |access-date=21 October 2024}}</ref> The trees are not generally [[frost]] hardy. They thrive in a consistently sunny, humid environment with fertile soil and adequate water.<ref name="RHS growing guide"/>

The color of citrus fruits only develops in climates with a ([[Diurnal temperature variation|diurnal]]) cool winter. In tropical regions with no winter at all, citrus fruits remain green until maturity, hence the tropical "green oranges".<ref>{{Cite web |url=https://plantscientist.wordpress.com/2014/12/04/why-is-my-orange-green/ |title=Why is my orange green? |last=Shailes |first=Sarah |date=4 December 2014 |website=Plant Scientist}}</ref> The terms 'ripe' and 'mature' are widely used synonymously, but they mean different things. A mature fruit is one that has completed its growth phase. [[Ripening]] is the sequence of changes within the fruit from maturity to the beginning of decay. These changes involve the conversion of starches to sugars, a decrease in acids, softening, and a change in the fruit's color.<ref name="ÖpikRolfe2005">{{cite book |first1=Helgi |last1=Öpik |first2=Stephen A. |last2=Rolfe |first3=Arthur John |last3=Willis |first4=Herbert Edward |last4=Street |title=The Physiology of Flowering Plants |year=2005 |publisher=[[Cambridge University Press]] |isbn=978-0-521-66251-2 |pages=309– }}</ref> ''Citrus'' fruits are non-[[climacteric (botany)|climacteric]] and respiration slowly declines and the production and release of ethylene is gradual.<ref name="Spiegel-RoyGoldschmidt1996">{{cite book |first1=Pinchas |last1=Spiegel-Roy |first2=Eliezer E. |last2=Goldschmidt |title=Biology of Citrus |url=https://books.google.com/books?id=S0-h00_-3CUC&pg=PA101 |access-date=31 July 2010 |year=1996 |publisher=Cambridge University Press |isbn=978-0-521-33321-4 |pages=101– }}</ref> 

=== Production ===

{{further|Citrus production}}

[[File:Hauptanbaugebiete-Zitrusfrüchte.svg|thumb|upright=1.35|Major producing regions]]

According to the [[UN Food and Agriculture Organization]], world production of all citrus fruits in 2016 was 124 million tonnes, with about half of this production as oranges.<ref name="fao16">{{cite web |title=Citrus fruit, fresh and processed: Statistical Bulletin |url=http://www.fao.org/3/a-i8092e.pdf |publisher=UN Food and Agriculture Organization |access-date=28 February 2020 |date=2016}}</ref> At US $15.2 billion equivalent in 2018, citrus trade<ref>https://oec.world/en/profile/hs/citrus?disaggregationYearSelector=tradeYear3 OEC — The Observer of Economic Complexity, Citrus</ref> makes up nearly half of the world fruit trade, which was US$32.1 billion that year.<ref>https://oec.world/en/profile/sitc/fruit OEC — The Observer of Economic Complexity, Fruit</ref> According to the [[United Nations Conference on Trade and Development]], citrus production grew during the early 21st century mainly by the increase in [[tillage|cultivation]] areas, improvements in transportation and packaging, rising incomes and consumer [[preference]] for healthy foods.<ref name=fao16/> In 2019–20, world production of oranges was estimated to be 47.5 million tonnes, led by Brazil, Mexico, the European Union, and China as the largest producers.<ref name="usda20">{{cite web |title=Citrus: World Markets and Trade |url=https://apps.fas.usda.gov/psdonline/circulars/citrus.pdf |publisher=US Department of Agriculture |access-date=28 February 2020 |date=1 January 2020}}</ref>

=== Pests and diseases ===

{{main list|List of citrus diseases}}

Among the diseases of citrus plantations are [[citrus black spot]] (a fungus), [[citrus canker]] (a bacterium), [[citrus greening]] (a bacterium, spread by an insect pest), and sweet orange scab (a fungus, ''Elsinöe australis'').<ref name="USDA 2024">{{cite web |title=Citrus diseases |url=https://www.aphis.usda.gov/plant-pests-diseases/citrus-diseases |website=U. S. Department of Agriculture Animal and Plant Health Inspection Service |access-date=20 October 2024 |date=22 August 2024}}</ref> Citrus plants are liable to infestation by [[ectoparasite]]s which act as [[Vector (epidemiology)|vectors]] to plant diseases: for example, aphids transmit the damaging [[citrus tristeza virus]],<ref>{{cite journal |last1=Lee |first1=Richard F. |title=Chapter Five - Control of Virus Diseases of Citrus |journal=Advances in Virus Research |date=2015 |volume=92 |pages=143–173 |doi=10.1016/bs.aivir.2014.10.002 |pmid=25591879 }}</ref> while the aphid-like [[Diaphorina citri|Asian citrus psyllid]] can carry the bacterium which causes the serious [[citrus greening disease]].<ref name="Alquezar-et-al-2021">{{cite journal |last1=Alquézar |first1=Berta |last2=Carmona |first2=Lourdes |last3=Bennici |first3=Stefania |last4=Peña |first4=Leandro |title=Engineering of citrus to obtain huanglongbing resistance |journal=[[Current Opinion in Biotechnology]] |publisher=[[Elsevier]] |volume=70 |year=2021 |doi=10.1016/j.copbio.2021.06.003 |pages=196–203 |s2cid=235712334 |pmid=34198205|doi-access=free |hdl=10251/189663 |hdl-access=free }}</ref><ref name="californiacitrusthreat">{{cite web |url=http://www.californiacitrusthreat.org/asian-citrus-psyllid.php |title=About the Asian Citrus Psyllid and Huanglongbing |work=californiacitrusthreat.org |access-date=30 November 2012 |archive-date=13 December 2012 |archive-url=https://web.archive.org/web/20121213014128/http://www.californiacitrusthreat.org/asian-citrus-psyllid.php |url-status=dead}}</ref> This threatens production in Florida,<ref>{{Cite web |url=https://www.nass.usda.gov/Statistics_by_State/Florida/Publications/Citrus/Citrus_Statistics/2015-16/fcs1516.pdf |title=Florida Citrus Statistics 2015–2016 |date=3 October 2017 |website=United States Department of Agriculture – National Agricultural Statistics Service|access-date=3 October 2017 |pages=62 |quote=Abandoned groves are a threat to the citrus industry and are a haven for psyllids carrying the bacterium that causes greening disease.}}</ref><ref>{{cite news |last=Nelson |first=Diane|title=Can Science Save Citrus? Farmers, researchers try to hold off deadly citrus greening long enough to find cure |date=27 August 2019 |url=https://www.ucdavis.edu/food/news/can-science-solve-citrus-greening-disease/ |access-date=20 September 2019}}</ref> California,<ref name="californiacitrusthreat"/> and worldwide. Citrus groves are attacked by parasitic [[Nematode]]s including citrus (''[[Tylenchulus semipenetrans]]'') and sheath nematodes (''[[Hemicycliophora]]'' spp.).<ref>{{Cite web |title=Nematodes / Citrus / Agriculture: Pest Management Guidelines / UC Statewide IPM Program |url=https://ipm.ucanr.edu/agriculture/citrus/nematodes/#gsc.tab=0 |access-date=2024-11-14 |website=ipm.ucanr.edu}}</ref><ref>A Sheath Nematode, Hemicycliophora arenaria raski, Pathogenic to Citrus, by D. E. Stokes, Florida Department of Agriculture and Consumer Services, July 1977[https://ccmedia.fdacs.gov/content/download/10832/file/nem029.pdf]</ref>

<gallery mode=packed>
File:Citrus Black Spot on Valencia orange (detail).jpg|[[Citrus black spot]] on a [[Valencia orange]]
File:CTV Leaf Chlorosis.jpg|[[Chlorosis]] caused by [[Citrus tristeza virus]]
File:Citrus canker on fruit.jpg|[[Citrus canker]], caused by the [[gammaproteobacterium]] ''Xanthomonas axonopodis''
File:Asian Citrus Psyllid adult (detail).jpg|[[Asian citrus psyllid]], [[Disease vector|vector]] of citrus greening disease
File:Huanglongbing (cropped).jpg|[[Citrus greening disease]] on [[mandarin orange]]
File:Life stages of citrus nematode.svg|Life stages of the citrus [[nematode]],''[[Tylenchulus semipenetrans]]''
</gallery>

=== Deficiency diseases ===

Citrus plants can develop the deficiency condition [[chlorosis]], characterized by yellowing leaves.<ref name="SumoGardener">Online at SumoGardener {{cite web |url=http://sumogardener.com/yellow-leaves-citrus-trees/ |title=How to Avoid Yellow Leaves on Citrus Trees |date=9 July 2016}}</ref> The condition is often caused by an excessively high [[pH]] ([[alkaline soil]]), which prevents the plant from absorbing nutrients such as iron, [[magnesium]], and [[zinc]] needed to produce [[chlorophyll]].<ref name=Mauk>{{cite web |last1=Mauk |first1=Peggy A. |last2=Shea |first2=Tom |title=Questions and Answers to Citrus Management (3rd ed.) |url=http://ucanr.edu/datastoreFiles/391-272.pdf |publisher=University of California Cooperative Extension |access-date=24 May 2014 |pages=7–8}}</ref>