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|image_alt=[[Botanical illustration]] of plant leaves and flowers
|image2=Manihot esculenta 001.jpg
|image2_caption=Starchy tuberous root[[Tuber]] (waxed)
|image2_alt=Photograph of oblong brown tuberous root, waxed
|genus=Manihot
|species=esculenta
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}}
 
'''''Manihot esculenta''''', [[common name|commonly called]] '''cassava''', '''manioc''',<!--<ref name=GRIN>{{GRIN |access-date=4 January 2014}}</ref>--> or '''yuca''' (among numerous regional names), is a woody [[shrub]] of the [[spurge]] family, [[Euphorbiaceae]], native to South America, from Brazil, Paraguay and parts of the Andes. Although a perennial plant, cassava is extensively cultivated in [[tropical]] and [[subtropical]] regions as an annual [[crop]] for its edible [[starch]]y [[tuber]]ous root. Cassava is predominantly consumed in boiled form, but substantial quantities are processed to extract cassava starch, called [[tapioca]], which is used for food, animal feed, and industrial purposes. The Brazilian {{lang|pt-BR|farinhafarofa}}, and the related ''[[garri]]'' of West Africa, is an edible coarse flour obtained by grating cassava roots, pressing moisture off the obtained grated pulp, and finally drying it (and roasting in the case of both {{lang|pt-BR|farinhafarofa}} and ''garri'').
 
Cassava is the third-largest source of carbohydrates in food in the tropics, after [[rice]] and [[maize]], making it an important [[staple food|staple]]; more than 500 million people depend on it. It offers the advantage of being exceptionally [[drought-tolerant]], and able to grow productively on poor soil. The largest producer is Nigeria, while Thailand is the largest exporter of cassava starch.
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== Description ==
 
The harvested part of a cassava plant is the root. This is long and tapered, with an easily detached rough brown rind. The white or yellowish flesh is firm and even in texture. Commercial [[cultivar]]s can be {{convert|5|to|10|cm|in|0}} wide at the top, and some {{convert|15|to|30|cm|in|0|abbr=on}} long, with a woody vascular bundle running down the middle. The [[tuber]]ous roots are largely [[starch]], with small amounts of calcium (16&nbsp;milligrams per 100&nbsp;grams), phosphorus (27&nbsp;mg/100&nbsp;g), and [[Vitamin C|vitamin&nbsp;C]] (20.6&nbsp;mg/100&nbsp;g).<ref>{{cite web|title=Basic Report: 11134, Cassava, raw|url=https://ndb.nal.usda.gov/ndb/foods/show/2907?manu=&fgcd=&ds=|archive-url=https://web.archive.org/web/20170712215400/https://ndb.nal.usda.gov/ndb/foods/show/2907?manu=&fgcd=&ds=|archive-date=12 July 2017|website=National Nutrient Database for Standard Reference Release 28|date=May 2016|publisher=Agricultural Research Service, US Department of Agriculture|access-date=7 December 2016}}</ref> Cassava roots contains little [[protein]], whereas the leaves are rich in proteinit,<ref>{{Cite journal |last1=Latif |first1=Sajid |last2=Müller |first2=Joachim |title=Potential of cassava leaves in human nutrition: a review |journal=[[Trends in Food Science & Technology]] |year=2015 |volume=44 |issue=2 |pages=147–158 |doi=10.1016/j.tifs.2015.04.006 }}</ref> except for being low in [[methionine]], an essential [[amino acid]].<ref>{{Cite journal|last=Ravindran|first=Velmerugu |title=Preparation of cassava leaf products and their use as animal feeds |journal=FAO Animal Production and Health Paper |issue=95 |pages=111–125 |year=1992 |url=http://www.fao.org/Ag/AGA/AGAP/FRG/AHPP95/95-111.pdf |access-date=13 August 2010 |archive-date=15 January 2012 |archive-url=https://web.archive.org/web/20120115022720/http://www.fao.org/Ag/AGA/AGAP/FRG/AHPP95/95-111.pdf |url-status=dead}}</ref>
 
<gallery class=center mode=nolines widths=180 heights=180>
File:Cassava plant.jpg|Cassava plant
File:Manihot esculenta dsc07325.jpg|Unprocessed tuberous roots
File:Manihot esculenta - cross section 2.jpg|StarchyTuberous root in cross-section
File:Cassava1 (3945716612).jpg |Leaf
File:Cassava2 (3945624614).jpg |Leaf detail
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=== Genome ===
 
The complete and haplotype-resolved African cassava (TME204) genome has been reconstructed and made available using the Hi-C technology.<ref name="qi">{{Cite journal |last1=Qi |first1=W. |last2=Lim |first2=Y. |last3=Patrignani |first3=A. |last4=Schläpfer |first4=P. |last5=Bratus-Neuenschwander |first5=A. |last6=Grüter |first6=S. |last7=Chanez |first7=C. |last8=Rodde |first8=N. |last9=Prat |first9=E. |last10=Vautrin |first10=S. |last11=Fustier |first11=M. |last12=Pratas |first12=D. |last13=Schlapbach |first13=R. |last14=Gruissem |first14=W. |display-authors=5 |year=2022 |title=The haplotype-resolved chromosome pairs of a heterozygous diploid African cassava cultivar reveal novel pan-genome and allele-specific transcriptome features |journal=[[GigaScience]] |volume=11 |doi=10.1093/gigascience/giac028 |pmid=35333302 |last12=Pratas |first12=D. |last13=Schlapbach |first13=R. |last14=Gruissem |first14=W.|pmc=8952263 }}</ref> The genome shows abundant novel gene loci with enriched functionality related to chromatin organization, meristem development, and cell responses.<ref name="qi" /> Differentially expressed transcripts of different haplotype origins were enriched for different functionality during tissue development. In each tissue, 20–30% of transcripts showed allele-specific expression differences with <2% of direction-shifting. Despite high gene synteny, the HiFi genome assembly revealed extensive chromosome rearrangements and abundant intra-genomic and inter-genomic divergent sequences, with significant structural variations mostly related to long terminal repeat retrotransposons.<ref name="qi" />
 
Although [[smallholder]]s are otherwise [[economic efficiency|economically inefficient]] producers, they are vital to productivity at particular times.<ref name="Challenges-Opportunities" /> Small cassava farmers are no exception.<ref name="Challenges-Opportunities" /> [[Crop genetic diversity|Genetic diversity]] is vital when productivity has declined due to [[crop pest|pests]] and [[List of cassava diseases|diseases]], and smallholders tend to retain less productive but more diverse [[gene pool]]s.<ref name="Challenges-Opportunities">{{cite journal |datelast1=2020McGregor |issn=0817-8038 |journalfirst1=PacificAndrew Economic Bulletin|publisherlast2=Asia Pacific PressManley |first5first2=MikeM. |first4last3=R.Tubuna |first3=S. |first2last4=M.Deo |first1first4=AndrewR. |last5=Bourke |last4first5=DeoMike |last3date=Tubuna2020 |last2journal=ManleyPacific Economic Bulletin|last1publisher=McGregorAsia Pacific Press |title=Pacific Island food security: situation, challenges and opportunities |hdl=1885/39234}}</ref>
 
{{ visible anchor |MeFT1 |MeFT2 |FLOWERING LOCUS T |FT |FT protein }} (FT) is a gene producing FT proteins which affect the formation of storage roots in many plants, including this one.<ref name="Development" /> Alleles in cassava include ''MeFT1'' and ''MeFT2''.<ref name="Development" /> ''MeFT1'' [[gene expression|expression]] in leaves seems to not be [[photoperiodic]], while ''MeFT2'' clearly is.<ref name="Development" /> ''MeFT1'' expression encourages motivation of [[sucrose]] towards the reproductive organs, as shown by experimental [[overexpression]] reducing storage root accumulation.<ref name="Development">{{cite journal |year=2021 |publisher=[[Annual Reviews (publisher)|Annual Reviews]] |issue=1 |volume=72 |pages=551–580 |first2=David |first4=Sophia |first1=Wolfgang |first3=Uwe |last4=Sonnewald |last3=Sonnewald |last2=Rüscher |last1=Zierer |issn=1543-5008 |journal=[[Annual Review of Plant Biology]] |doi=10.1146/annurev-arplant-080720-084456 |title=Tuber and Tuberous Root Development |pmid=33788583 |doi-access=free }}</ref>
 
== History ==
 
[[File:Taíno women preparing cassava bread.png|thumb|[[Taíno]] women preparing [[cassava bread]] in 1565: grating yucatuberous roots into paste, shaping the bread, and cooking it on a fire-heated burén]]
[[File:Albert_Eckhout_-_Mandioca.jpg|thumb|17th-century painting by [[Albert Eckhout]] in [[Dutch Brazil]]]]
 
Wild populations of ''M. esculenta'' subspecies ''flabellifolia'', shown to be the progenitor of domesticated cassava, are centered in west-central Brazil, where it was likely first domesticated no more than 10,000 years ago.<ref>{{Cite journal|last1=Olsen|first1=K. M. |last2=Schaal |first2=B. A. |title=Evidence on the origin of cassava: phylogeography of ''Manihot esculenta'' |journal=[[Proceedings of the National Academy of Sciences of the United States of America]]|volume=96 |issue=10 |pages=5586–5591 |year=1999 |pmid=10318928 |pmc=21904 |bibcode=1999PNAS...96.5586O |doi=10.1073/pnas.96.10.5586 |doi-access=free }}</ref> Forms of the modern domesticated species can also be found growing in the wild in the south of Brazil. By 4600&nbsp;BC, cassava pollen appears in the [[Gulf of Mexico]] lowlands, at the [[San Andrés (Mesoamerican site)|San Andrés]] archaeological site.<ref>{{cite journal |doi=10.1126/science.292.5520.1370 |pmid=11359011 |bibcode=2001Sci...292.1370P |title=Origin and Environmental Setting of Ancient Agriculture in the Lowlands of Mesoamerica |journal=[[Science (journal)|Science]] |volume=292 |issue=5520 |pages=1370–1373 |last1=Pope |first1=Kevin O. |last2=Pohl |first2=Mary E. D. |last3=Jones |first3=John G. |last4=Lentz |first4=David L. |last5=von Nagy |first5=Christopher |last6=Vega |first6=Francisco J. |last7=Quitmyer |first7=Irvy R. |title=Origin and Environmental Setting of Ancient Agriculture in the Lowlands of Mesoamerica |journal=[[Science (journal)|Science]] |volume=292 |issue=5520 |pages=1370–1373 |year=2001 |doi=10.1126/science.292.5520.1370 |pmid=11359011 |bibcode=2001Sci...292.1370P}}</ref> The oldest direct evidence of cassava cultivation comes from a 1,400-year-old [[Maya civilization|Maya]] site, [[Joya de Cerén]], in [[El Salvador]].<ref>{{cite news |last=Carroll |first=Rory |title=CU team discovers Mayan crop system |newspaper=[[The Guardian]] |date=23 August 2007 |url=https://www.theguardian.com/science/2007/aug/23/1 |access-date=31 July 2019 |archive-date=31 July 2019 |archive-url=https://web.archive.org/web/20190731171801/https://www.theguardian.com/science/2007/aug/23/1 |url-status=live }}</ref> It became a [[staple food]] of the native populations of northern South America, southern Mesoamerica, and the [[Taíno|Taino]] people in the [[List of Caribbean islands|Caribbean islands]], who grew it using a high-yielding form of [[shifting cultivation|shifting agriculture]] by the time of European contact in 1492.<ref>{{cite web |title=Taino {{!}} History & Culture |url=https://www.britannica.com/topic/Taino |access-date=2020-09-24 |website=Encyclopedia Britannica |archive-date=2020-09-01 |archive-url=https://web.archive.org/web/20200901154607/https://www.britannica.com/topic/Taino |url-status=live}}</ref> Cassava was a staple food of [[pre-Columbian]] peoples in the Americas and is often portrayed in [[Pre-Columbian art|indigenous art]]. The [[Moche (culture)|Moche]] people often depicted yucacassava in their ceramics.<ref>Berrin, Katherine & Larco Museum. ''The Spirit of Ancient Peru:Treasures from the [[Larco Museum|Museo Arqueológico Rafael Larco Herrera]].'' New York: [[Thames & Hudson]], 1997.</ref>
 
[[Spaniards]] in their early occupation of Caribbean islands did not want to eat cassava or maize, which they considered insubstantial, dangerous, and not nutritious. They much preferred foods from Spain, specifically wheat bread, olive oil, red wine, and meat, and considered maize and cassava damaging to Europeans.<ref>Earle, Rebecca (2012) ''The Body of the Conquistador: Food, Race, and the Colonial Experience in Spanish America, 1492–1700''. New York: Cambridge University Press. pp. 54–57, 151. {{ISBN|978-1107693296}}.</ref> The cultivation and consumption of cassava were nonetheless continued in both Portuguese and Spanish America. Mass production of cassava bread became the first Cuban industry established by the Spanish.<ref>{{cite book|author=Long, Janet |url=https://books.google.com/books?id=Rn9LZ2XrIWgC&pg=PA75 |title=Conquest and food: consequences of the encounter of two worlds; page 75|publisher=UNAM|date=2003 |isbn=978-9703208524 |access-date=24 August 2020 |archive-date=20 April 2023|archive-url=https://web.archive.org/web/20230420125914/https://books.google.com/books?id=Rn9LZ2XrIWgC&pg=PA75 |url-status=live}}</ref> Ships departing to Europe from Cuban ports such as [[Havana]], [[Santiago de Cuba|Santiago]], [[Bayamo]], and [[Baracoa]] carried goods to Spain, but sailors needed to be provisioned for the voyage. The Spanish also needed to replenish their boats with dried meat, water, fruit, and large amounts of cassava bread.<ref>{{cite web|url=http://www.sjsu.edu/faculty/watkins/havana.htm |title=The Economic History of Havana, Cuba: A City So Beautiful and Important It Was Once Worth More Than All of Florida |author=Watkins, Thayer|publisher=San José State University, Department of Economics|date=2006|access-date=20 August 2015 |archive-url=https://web.archive.org/web/20160502042108/http://www.sjsu.edu/faculty/watkins/havana.htm |archive-date=2 May 2016}}</ref> Sailors complained that it caused them digestive problems.<ref>{{cite journal |author=Super, John C. |title=Spanish Diet in the Atlantic Crossing|journal=[[Terrae Incognitae]] |volume=16 |year=1984 |pages=60–63 |doi=10.1179/008228884791016718}}</ref>
 
Portuguese traders introduced cassava to Africa from Brazil in the 16th century. Around the same period, it was also introduced to Asia through [[Columbian Exchange]] by Portuguese and Spanish traders, who planted it in their colonies in Goa, Malacca, Eastern Indonesia, Timor and the Philippines.<ref name="Nweke 2005">{{cite book |last=Nweke |first=Felix I. |chapter=The cassava transformation in Africa |chapter-url=http://www.fao.org/docrep/009/a0154e/A0154E02.HTM |publisher=The Food and Agriculture Organization of the United Nations |place=Rome |year=2005 |title=A review of cassava in Africa with country case studies on Nigeria, Ghana, the United Republic of Tanzania, Uganda and Benin |series=Proceedings of the Validation Forum on the Global Cassava Development Strategy |volume=2 |access-date=1 January 2011 |archive-date=11 February 2019 |archive-url=https://web.archive.org/web/20190211073843/http://www.fao.org/docrep/009/a0154e/A0154E02.htm |url-status=live}}</ref> Cassava has also become an important crop in Asia. While it is a valued food staple in parts of eastern Indonesia, it is primarily cultivated for starch extraction and bio-fuel production in Thailand, Cambodia and Vietnam.<ref>{{Cite book |last=Hershey |first=Clair |display-authors=et al |date=April 2000 |chapter-url=http://www.fao.org/docrep/009/y1177e/Y1177E02.htm |publisher=Food and Agriculture Organization of the United Nations |title=A review of cassava in Asia with country case studies on Thailand and Viet Nam |chapter=Cassava in Asia. Expanding the Competitive Edge in Diversified Markets |place=Rome |access-date=28 January 2018 |archive-date=7 November 2017|archive-url=https://web.archive.org/web/20171107231144/http://www.fao.org/docrep/009/y1177e/Y1177E02.htm|url-status=live}}</ref> Cassava is sometimes described as the "bread of the tropics"<ref>{{Cite book |last1=Adams |first1=C. |last2=Murrieta |first2=R. |last3=Siqueira |first3=A. |last4=Neves |first4=W. |last5=Sanches |first5=R. |chapter=Bread of the Land: The Invisibility of Manioc in the Amazon |title=Amazon Peasant Societies in a Changing Environment |doi=10.1007/978-1-4020-9283-1_13 |pages=281–305 |year=2009 |isbn=978-1-4020-9282-4 }}</ref> but should not be confused with the tropical and equatorial [[bread tree]] ''(Encephalartos)'', the [[breadfruit]] ''(Artocarpus altilis)'' or the [[African breadfruit]] ''(Treculia africana)''. This description definitely holds in Africa and parts of South America; in Asian countries such as Vietnam fresh cassava barely features in human diets.<ref name=MotaGuttierez2019>{{cite journal |last1=Mota-Guttierez |first1=Jatziri |last2=O'Brien |first2=Gerard Michael |date=September 2019 |title=Cassava consumption and the occurrence of cyanide in cassava in Vietnam, Indonesia and Philippines |journal=Public Health Nutrition |volume=23 |issue=13 |pages=2410–2423 |doi=10.1017/S136898001900524X |doi-access=free |pmid=32438936 |pmc=11374567 }}</ref>
 
There is a legend that cassava was introduced in 1880–1885&nbsp;CE to the South Indian state of [[Kerala]] by the King of [[Travancore]], Vishakham Thirunal Maharaja, after a great famine hit the kingdom, as a substitute for rice.<ref name=Saraswathy2019>{{cite web |date=June 27, 2019 |author=Saraswathy Nagarajan |url=https://www.thehindu.com/life-and-style/food/how-tapioca-came-to-travancore/article28181288.ece |title=How tapioca came to Travancore |work=The Hindu |archive-url=https://web.archive.org/web/20200727082403/https://www.thehindu.com/life-and-style/food/how-tapioca-came-to-travancore/article28181288.ece |archive-date=27 July 2020 |url-status=live}}</ref> However, there are documented cases of cassava cultivation in parts of the state before the time of Vishakham Thirunal Maharaja.<ref>{{Cite book |last1=Ainslie |first1=Whitelaw |url=http://archive.org/details/b28037340 |title=Materia medica of Hindoostan, and artisan's and agriculturalist's nomenclature |last2=Halford|first2=Henry|date=1813|publisher=Government Press |location=Madras State}}</ref> Cassava is called kappa or maricheeni in [[Malayalam]], and [[tapioca]] in Indian English usage.<ref>{{cite web |title=Kappa for all seasons - many avatars of the magic starch root... |url=https://www.onmanorama.com/food/features/2018/01/30/kappa-for-all-seasons.html |website=Onmanorama |location=[[Kerala]], India |access-date=11 May 2024 |date=1 February 2018}}</ref>
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; Bacteria
 
Among the most serious bacterial pests is [[Xanthomonas axonopodis pv. manihotis|''Xanthomonas axonopodis'' pv. ''manihotis'']], which causes [[bacterial blight of cassava]]. This disease originated in South America and has followed cassava around the world.<ref name="Lozano-1986">{{Cite journal |last=Lozano |first=J. Carlos |date=September 1986 |title=Cassava bacterial blight: a manageable disease |url=http://www.apsnet.org/publications/PlantDisease/BackIssues/Documents/1986Articles/PlantDisease70n12_1089.PDF |journal=[[Plant Disease (journal)|Plant Disease]] |publisher=[[American Phytopathological Society]] (APS) |volume=70 |issue=12 |pages=1089–1093 |doi=10.1094/PD-70-1089 |access-date=14 January 2023 |archive-date=14 January 2023 |archive-url=https://web.archive.org/web/20230114224139/https://www.apsnet.org/publications/PlantDisease/BackIssues/Documents/1986Articles/PlantDisease70n12_1089.PDF |url-status=live }}</ref> Bacterial blight has been responsible for near catastrophic losses and famine in past decades, and its mitigation requires active management practices.<ref name="Lozano-1986" /> Several other bacteria attack cassava, including the related ''[[Xanthomonas campestris]]'' pv. ''cassavae'', which causes bacterial angular leaf spot.<ref name="Zárate‐ChavesZárate-Chaves 2021">{{cite journal |last1=Zárate-Chaves |first1=Carlos A. |last2=Gómez de la Cruz |first2=Diana |last3=Verdier |first3=Valérie |last4=López |first4=Camilo E. |last5=Bernal |first5=Adriana |last6=Szurek |first6=Boris |title=Cassava diseases caused by Xanthomonas phaseoli pv. manihotis and Xanthomonas cassavae |journal=Molecular Plant Pathology |volume=22 |issue=12 |date=2021 |issn=1464-6722 |pmid=34227737 |pmc=8578842 |doi=10.1111/mpp.13094 |pages=1520–1537}}</ref>
 
; Fungi
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; Nematodes
 
Nematode pests of cassava are thought to cause harms ranging from negligible to seriously damaging,<ref>{{cite journal |author1=Coyne, D. L. |author2=Talwana, L. A. H. |date=2000 |title=Reaction of cassava cultivars to root-knot nematode (''Meloidogyne'' spp.) in pot experiments and farmer-managed field trials in Uganda |journal=International Journal of Nematology|volume=10 |pages=153–158 |url=https://www.cabdirect.org/cabdirect/abstract/20013117434 |access-date=22 September 2018}}</ref><ref>{{cite journal |author1=Makumbi-Kidza, N. N. |author2=Speijer |author3=Sikora R. A. |date=2000 |title=Effects of ''Meloidogyne incognita'' on growth and storage-root formation of cassava (''Manihot esculenta'') |journal=Journal of Nematology|volume=32 |issue=4S |pages=475–477 |pmc=2620481 |pmid=19270997}}</ref><ref name="Gapasin"/> making the choice of management methods difficult.<ref name="Coyne"/> A wide range of plant parasitic nematodes have been reported associated with cassava worldwide. These include ''[[Pratylenchus brachyurus]]'', ''[[Rotylenchulus reniformis]]'', ''[[Helicotylenchus]]'' spp., ''[[Scutellonema]]'' spp. and ''[[Root-knot nematode|Meloidogyne]]'' spp., of which ''[[Meloidogyne incognita]]'' and ''[[Meloidogyne javanica]]'' are the most widely reported and economically important.<ref>{{cite journal |author1=Mc Sorley, R. |author2=Ohair, S. K. |author3=Parrado, J. L. |date=1983 |title=Nematodes of Cassava, ''Manihot esculenta'' Crantz |url=http://journals.fcla.edu/nematropica/article/view/63820/61488 |journal=Nematropica|volume=13 |pages=261–287 |archive-url=https://web.archive.org/web/20160603205439/http://journals.fcla.edu/nematropica/article/view/63820/61488 |archive-date=3 June 2016 |access-date=4 May 2016}}</ref> ''Meloidogyne'' spp. feeding produces physically damaging galls with eggs inside them. Galls later merge as the females grow and enlarge, and they interfere with water and nutrient supply.<ref name="Gapasin">{{cite journal |author1=Gapasin, R. M. |date=1980 |title=Reaction of golden yellow cassava to ''Meloidogyne'' spp. Inoculation |journal=Annals of Tropical Research|volume=2 |pages=49–53}}</ref> Cassava roots become tough with age and restrict the movement of the juveniles and the egg release. It is therefore possible that extensive galling can be observed even at low densities following infection.<ref name="Coyne">{{cite journal |author1=Coyne, D. L. |date=1994 |title=Nematode pests of cassava |journal=African Crop Science Journal|volume=2 |issue=4 |pages=355–359 |url=https://www.ajol.info/index.php/acsj/article/view/135776 |access-date=22 September 2018 |archive-date=22 September 2018 |url-status=live |archive-url=https://web.archive.org/web/20180922101847/https://www.ajol.info/index.php/acsj/article/view/135776}}</ref> Other pests and diseases can gain entry through the physical damage caused by gall formation, leading to rots. They have not been shown to cause direct damage to the enlarged storagetuberous roots, but plantsplant height can havebe reduced height if therethe wasroot losssystem ofis enlarged root weightreduced.<ref>{{cite journal |author1=Caveness, F. E. |date=1982 |title=Root-knot nematodes as parasites of cassava |journal=IITA Research Briefs|volume=3 |issue=2 |pages=2–3}}</ref>
Nematicides reduce the numbers of galls per feeder root, along with fewer rots in the storagetuberous roots.<ref>{{cite journal |author1=Coyne D. L. |author2=Kagoda F. |author3=Wambugu E. |author4=Ragama P. |date=2006 |title=Response of cassava to nematicide application and plant-parasitic nematode infection in East Africa, with emphasis on root-knot nematode |journal=International Journal of Pest Management |volume=52 |issue=3 |pages=215–223 |doi=10.1080/09670870600722959 |s2cid=84771539}}</ref> The organophosphorus nematicide femaniphos does not reduce crop growth or harvest yield. Nematicide use in cassava is not terribly effective at increasing harvested yield, but lower infestation at harvest and lower subsequent storage loss provide a higher effective yield. The use of tolerant and resistant cultivars is the most practical management method in most locales.<ref name="Coyne-et-al-2018">{{cite journal |last1=Coyne |first1=Danny L. |last2=Cortada |first2=Laura |last3=Dalzell |first3=Johnathan J. |last4=Claudius-Cole |first4=Abiodun O. |last5=Haukeland |first5=Solveig |last6=Luambano |first6=Nessie |last7=Talwana |first7=Herbert |date=2018-08-25 |title=Plant-Parasitic Nematodes and Food Security in Sub-Saharan Africa |journal=[[Annual Review of Phytopathology]] |publisher=[[Annual Reviews (publisher)|Annual Reviews]] |volume=56 |issue=1 |pages=381–403 |doi=10.1146/annurev-phyto-080417-045833 |issn=0066-4286 |pmc=7340484 |pmid=29958072 |s2cid=49615468}}</ref><ref name="Coyne"/><ref name="TodayNg-new-varieties">{{cite web |url=http://www.today.ng/news/nigeria/nigeria-introduce-cassava-varieties-334463 |title=Nigeria to introduce new cassava varieties |website=Todayng |date=2020-12-21 |first=Chidinma |last=Uchechukwumgemezu |access-date=21 December 2020 |archive-date=21 December 2020 |archive-url=https://web.archive.org/web/20201221194624/https://www.today.ng/news/nigeria/nigeria-introduce-cassava-varieties-334463 |url-status=live}}</ref>
 
; Insects
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=== Harvesting ===
 
Before harvest, the leafy stems are removed. The harvest is gathered by pulling up the base of the stem and cutting off the tuberous roots.<ref name=CIAT/>
 
=== Handling and storage ===
 
Cassava deteriorates after harvest, when the tuberous roots are first cut. The healing mechanism produces [[coumaric acid]], which oxidizes and blackens the roots, making them inedible after a few days. This deterioration is related to the accumulation of [[reactive oxygen species]] initiated by cyanide release during mechanical harvesting. Cassava shelf life may be increased up to three weeks by overexpressing a cyanide-insensitive alternative oxidase, which suppressed ROS by 10-fold.<ref>{{cite journal |last1=Zidenga |first1=T |display-authors=etal |year=2012 |title=Extending cassava root shelf life via reduction of reactive oxygen species production |journal=[[Plant Physiology (journal)|Plant Physiology]]|volume=159 |issue=4 |pages=1396–1407 |doi=10.1104/pp.112.200345 |pmc=3425186 |pmid=22711743}}</ref> Post-harvest deterioration is a major obstacle to the export of cassava. Fresh cassava can be preserved like potato, using [[thiabendazole]] or bleach as a fungicide, then wrapping in plastic, freezing, or applying a wax coating.<ref>{{cite web |title=Storage and processing of roots and tubers in the tropics |url=http://www.fao.org/docrep/x5415e/x5415e04.htm |access-date=4 May 2016 |publisher=[[U.N. Food and Agriculture Organization]] |archive-date=22 April 2016 |archive-url=https://web.archive.org/web/20160422120308/http://www.fao.org/docrep/x5415e/x5415e04.htm |url-status=live }}</ref>
 
While alternative methods for controlling post-harvest deterioration have been proposed, such as preventing reactive oxygen species effects by using plastic bags during storage and transport, coating the roots with wax, or freezing roots, such strategies have proved to be economically or technically impractical, leading to [[plant breeding|breeding]] of cassava varieties with improved durability after harvest, achieved by different mechanisms.<ref name="gmr">{{cite journal |last1=Venturini |first1=M. T |last2=Santos |first2=L. R |last3=Vildoso |first3=C. I |last4=Santos |first4=V. S |last5=Oliveira |first5=E. J |year=2016 |title=Variation in cassava germplasm for tolerance to post-harvest physiological deterioration |journal=[[Genetics and Molecular Research]] |volume=15 |issue=2 |doi=10.4238/gmr.15027818 |pmid=27173317 |doi-access=free}}</ref><ref name="cs">{{cite journal |last1=Morante |first1=N. |last2=Sánchez |first2=T. |last3=Ceballos |first3=H. |last4=Calle |first4=F. |last5=Pérez |first5=J. C. |last6=Egesi |first6=C. |last7=Cuambe |first7=C. E. |last8=Escobar |first8=A. F. |last9=Ortiz |first9=D. |last10=Chávez |first10=A. L. |last11=Fregene |first11=M. |year=2010 |title=Tolerance to Postharvest Physiological Deterioration in Cassava Roots |journal=[[Crop Science (journal)|Crop Science]]|volume=50 |issue=4 |pages=1333–1338 |doi=10.2135/cropsci2009.11.0666}}</ref> One approach used [[gamma ray]]s to try to silence a gene involved in triggering deterioration; another strategy selected for plentiful [[carotenoid]]s, [[antioxidant]]s which may help to reduce oxidization after harvest.<ref name="cs" />
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Like many other roots and tubers, both bitter and sweet varieties of cassava contain [[antinutrient|antinutritional]] factors and toxins, with the bitter varieties containing much larger amounts.<ref name="fao.org">{{cite book |publisher=[[Food and Agriculture Organization]] of the United Nations (FAO) |year=1990 |title=Roots, tubers, plantains and bananas in human nutrition |chapter=Ch. 7 Toxic substances and antinutritional factors |chapter-url=http://www.fao.org/docrep/t0207e/T0207E08.htm#Cassava%20toxicity |place=Rome |isbn=9789251028629|url-access=registration |url=https://archive.org/details/rootstubersplant0000unse}}</ref> The more toxic varieties of cassava have been used in some places as [[famine food]] during times of [[food insecurity]].<ref name="promedmail-4799579" /><ref name="fao.org"/> For example, during the [[shortages in Venezuela]] in the late 2010s, dozens of deaths were reported due to Venezuelans resorting to eating bitter cassava in order to curb starvation.<ref>{{cite news |last1=Castro |first1=Maolis |date=6 March 2017 |title=La yuca amarga alimenta la muerte en Venezuela |language=es |work=[[El País]] |url=https://elpais.com/internacional/2017/03/05/america/1488744764_611719.html |access-date=25 February 2018 |archive-date=12 February 2018 |archive-url=https://web.archive.org/web/20180212184804/https://elpais.com/internacional/2017/03/05/america/1488744764_611719.html |url-status=live }}</ref><ref>{{cite news |date=22 February 2018 |title=Estragos de la crisis: Ocho niños han muerto en Aragua por consumir yuca amarga |language=es-ES |work=[[La Patilla]] |url=https://www.lapatilla.com/site/2018/02/22/estragos-de-la-crisis-ocho-ninos-han-muerto-en-aragua-por-consumir-yuca-amarga/ |access-date=25 February 2018 |archive-date=23 February 2018 |archive-url=https://web.archive.org/web/20180223022727/https://www.lapatilla.com/site/2018/02/22/estragos-de-la-crisis-ocho-ninos-han-muerto-en-aragua-por-consumir-yuca-amarga/ |url-status=live }}</ref> Cases of cassava poisoning were also documented during the famine accompanying the [[Great Leap Forward]] (1958–1962) in China.<ref>{{cite book |author=Zhou Xun |title=The Great Famine in China, 1958-1962: A Documentary History |publisher=Yale University Press |year=2012 |chapter=Ch. 3 Seasons of death}}</ref> Farmers may select bitter cultivars to reduce crop losses.<ref name="leisa">{{cite magazine |author1=Chiwona-Karltun, Linley |author2=Katundu, Chrissie |author3=Ngoma, James |author4=Chipungu, Felistus |author5=Mkumbira, Jonathan |author6=Simukoko, Sidney |author7=Jiggins, Janice |year=2002 |title=Bitter cassava and women: an intriguing response to food security |magazine=LEISA Magazine |volume=18 |issue=4 |url=https://www.researchgate.net/publication/255687456 |access-date=22 September 2018 |archive-date=22 September 2018 |archive-url=https://web.archive.org/web/20180922101746/https://www.researchgate.net/publication/255687456 |url-status=live }}</ref>
 
Societies that traditionally eat cassava generally understand that some processing (soaking, cooking, fermentation, etc.) is necessary to avoid getting sick. Brief soaking (four hours) of cassava is not sufficient, but soaking for 18–24 hours can remove up to half the level of cyanide. Drying may not be sufficient, either.<ref name="fao.org"/>
 
For some smaller-rooted, sweet varieties, cooking is sufficient to eliminate all toxicity. The cyanide is carried away in the processing water and the amounts produced in domestic consumption are too small to have environmental impact.<ref name="cereda" /> The larger-rooted, bitter varieties used for production of flour or starch must be processed to remove the cyanogenic glucosides. The large roots are peeled and then ground into flour, which is then soaked in water, squeezed dry several times, and toasted. The starch grains that flow with the water during the soaking process are also used in cooking.<ref>{{Cite journal |last1=Padmaja |first1=G. |last2=Steinkraus |first2=K. H. |year=1995 |title=Cyanide detoxification in cassava for food and feed uses |journal=[[Critical Reviews in Food Science and Nutrition]]|volume=35 |issue=4 |pages=299–339 |doi=10.1080/10408399509527703 |pmid=7576161}}</ref> The flour is used throughout South America and the [[Caribbean]]. Industrial production of cassava flour, even at the cottage level, may generate enough cyanide and cyanogenic glycosides in the effluents to have a severe environmental impact.<ref name="cereda"/>
 
==Uses==
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=== Preparation of bitter cassava ===
 
A safe processing method known as the "wetting method" is to mix the cassava flour with water into a thick paste, spread it in a thin layer over a basket and then let it stand for five hours at 30&nbsp;°C in the shade.<ref name="fca">{{cite journal |last1=Bradbury |first1=J.H. |date=2006 |title=Simple wetting method to reduce cyanogen content of cassava flour |url=http://biology-assets.anu.edu.au/hosted_sites/CCDN/papers/Howard_06.pdf |journal=[[Journal of Food Composition and Analysis]] |volume=19 |issue=4 |pages=388–393 |doi=10.1016/j.jfca.2005.04.012 |access-date=23 March 2018 |archive-date=5 February 2015 |archive-url=https://web.archive.org/web/20150205063243/http://biology-assets.anu.edu.au/hosted_sites/CCDN/papers/Howard_06.pdf |url-status=live }}</ref> In that time, about 83% of the cyanogenic [[glycoside]]s are broken down by [[linamarase]]; the resulting hydrogen cyanide escapes to the atmosphere, making the flour safe for consumption the same evening.<ref name="fca" />
 
The traditional method used in West Africa is to peel the roots and put them into water for three days to ferment. The roots are then dried or cooked. In Nigeria and several other west African countries, including Ghana, Cameroon, Benin, Togo, Ivory Coast, and Burkina Faso, they are usually grated and lightly fried in palm oil to preserve them. The result is a foodstuff called [[garri]]. Fermentation is also used in other places such as Indonesia, such as [[Tapai]]. The fermentation process also reduces the level of antinutrients, making the cassava a more nutritious food.<ref>{{cite journal |last1=Oboh |first1=G. |last2=Oladunmoye |first2=M.K. |title=Biochemical Changes in Micro-Fungi Fermented Cassava Flour Produced from Low- and Medium-Cyanide Variety of Cassava Tubers |journal=Nutrition and Health |volume=18 |issue=4 |date=2007 |issn=0260-1060 |doi=10.1177/026010600701800405 |pages=355–367|pmid=18087867 }}</ref> The reliance on cassava as a food source and the resulting exposure to the [[goitrogen]]ic effects of [[thiocyanate]] has been responsible for the endemic goiters seen in the [[Akoko]] area of southwestern Nigeria.<ref name="pmid10497657">{{cite journal |last1=Akindahunsi |first1=A. A. |last2=Grissom |first2=F. E. |last3=Adewusi |first3=S. R. |last4=Afolabi |first4=O. A. |last5=Torimiro |first5=S. E. |last6=Oke |first6=O. L. |title=Parameters of thyroid function in the endemic goitre of Akungba and Oke-Agbe villages of Akoko area of southwestern Nigeria |journal=African Journal of Medicine and Medical Sciences |volume=27 |issue=3–4 |date=1998 |issn=0309-3913 |pmid=10497657 |pages=239–242}}</ref><ref>{{cite journal |last1=Bumoko |first1=G.M.-M. |last2=Sadiki |first2=N.H. |last3=Rwatambuga |first3=A. |last4=Kayembe |first4=K.P. |last5=Okitundu |first5=D.L. |last6=Mumba Ngoyi |first6=D. |last7=Muyembe |first7=J.-J.T. |last8=Banea |first8=J.-P. |last9=Boivin |first9=M.J. |last10=Tshala-Katumbay |first10=D. |title=Lower serum levels of selenium, copper, and zinc are related to neuromotor impairments in children with konzo |journal=Journal of the Neurological Sciences |volume=349 |issue=1–2 |date=2015 |pmid=25592410 |pmc=4323625 |doi=10.1016/j.jns.2015.01.007 |pages=149–153}}</ref>
 
<gallery class=center mode=nolines widths=180 heights=180><!--arrange images to stop'em running into next section-->
File:PeeledCassava.jpg|RootTuber, peeled and soaking to reduce toxicity
</gallery>
 
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===Animal feed===
 
Cassava rootstubers and hay are used worldwide as animal feed. Young cassava hay is harvested at three to four month, when it reaches about {{convert|30|to|45|cm|abbr=on}} above ground; it is dried in the sun until its dry matter content approaches 85 percent. The hay contains 20–27 percent [[Protein (nutrient)|protein]] and 1.5–4 percent [[tannin]]. It is valued as a source of roughage for [[ruminant]]s such as cattle.<ref>{{cite journal |author1=R. Lunsin |author2=M. Wanapat |author3=P. Rowlinson |title=Effect of cassava hay and rice bran oil supplementation on rumen fermentation, milk yield and milk composition in lactating dairy cows |journal=[[Asian-Australasian Journal of Animal Sciences]]|date=October 2012 |volume=25 |issue=10 |pages=1364–1373 |doi=10.5713/ajas.2012.12051 |pmc=4093022 |pmid=25049491}}</ref>
 
<gallery class=center mode=nolines widths=180 heights=180><!--format prevents images becoming very large at some window widths-->
File:Cassava being grated.jpg|RootsTubers being grated
File:Close-up of grated cassava.jpg|A close-up of the product
File:Cassava drying on a road.jpg|Drying on road to be used for pig and chicken feed