Amaranthus retroflexus (redroot pigweed)
Index
- Pictures
- Identity
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Description
- Distribution
- Distribution Table
- Habitat
- Habitat List
- Hosts/Species Affected
- Host Plants and Other Plants Affected
- Biology and Ecology
- Natural enemies
- Notes on Natural Enemies
- Impact
- Uses
- Uses List
- Similarities to Other Species/Conditions
- Prevention and Control
- References
- Distribution Maps
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Top of pagePreferred Scientific Name
- Amaranthus retroflexus L. (1753)
Preferred Common Name
- redroot pigweed
International Common Names
- English: carelessweed; common amaranth; redroot
- Spanish: amaranto; aracu; atacu; bledo; bledo rojo; marxant; quelite; quentonil
- French: amarante récourbée; amarante réfléchie
- Portuguese: caruru gigante; moncos-de-Peru
Local Common Names
- Argentina: atac; ataco; caa-ruru; yuyo colorado
- Bolivia: ataco coman; chiori
- Brazil: bredo; carura aspero; caruru
- Canada: amarante a racine rouge
- Denmark: opret anarant; tilbagebjet anarant
- Finland: vihrea revonhanta
- Germany: Amarant (Rauhhaariger); Fuchsschwanz; Krummer Fuchsschwanz; Rauhhaariger Amarant; Zuruckgekrummter; Zurueckgebogener Amarant
- Iran: taj khoroos
- Italy: amaranto; amaranto comune; biedone
- Japan: aogeito
- Madagascar: amatarika
- Netherlands: papegaaienkruid
- Norway: duskamarant
- Peru: yuyo
- Sweden: svinamarant
- Turkey: horoz kuyruga; kirmizi koklu tilki kuyrugu
- Venezuela: pira
- Yugoslavia (Serbia and Montenegro): hrapavi stir
EPPO code
- AMARE (Amaranthus retroflexus)
Taxonomic Tree
Top of page- Domain: Eukaryota
- Kingdom: Plantae
- Phylum: Spermatophyta
- Subphylum: Angiospermae
- Class: Dicotyledonae
- Order: Caryophyllales
- Family: Amaranthaceae
- Genus: Amaranthus
- Species: Amaranthus retroflexus
Notes on Taxonomy and Nomenclature
Top of pageA. retroflexus has a diploid chromosome number of 34 (Murray, 1940; Grant, 1959). It readily hybridizes with closely related species (A. hybridus, A. powellii and A. caudatus), but the F1 generation is highly sterile (Murray 1940). Hybrids often have oddly shaped inflorescences.
Description
Top of pageDistribution
Top of pageDistribution Table
Top of pageThe distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.
Last updated: 14 Feb 2022Continent/Country/Region | Distribution | Last Reported | Origin | First Reported | Invasive | Reference | Notes |
---|---|---|---|---|---|---|---|
Africa |
|||||||
Egypt | Present | Introduced | 1956 | ||||
Morocco | Present | ||||||
Mozambique | Present, Widespread | ||||||
South Africa | Present | ||||||
Tanzania | Present, Widespread | ||||||
Tunisia | Present, Widespread | ||||||
Asia |
|||||||
Afghanistan | Present, Widespread | ||||||
China | Present | Introduced | 1849 | ||||
-Anhui | Present | ||||||
-Heilongjiang | Present | ||||||
-Shandong | Present | ||||||
India | Present | ||||||
-Punjab | Present | ||||||
Iran | Present, Widespread | ||||||
Israel | Present, Widespread | ||||||
Japan | Present, Widespread | ||||||
Jordan | Present, Widespread | ||||||
Lebanon | Present, Widespread | ||||||
Nepal | Present | ||||||
North Korea | Present, Widespread | ||||||
Pakistan | Present | ||||||
South Korea | Present, Widespread | ||||||
Taiwan | Present | Introduced | 2004 | ||||
Turkey | Present, Widespread | ||||||
Uzbekistan | Present | ||||||
Europe |
|||||||
Albania | Present | Introduced | 1895 | ||||
Austria | Present, Widespread | ||||||
Belgium | Present | Introduced | 1857 | ||||
Bosnia and Herzegovina | Present, Widespread | ||||||
Bulgaria | Present, Widespread | ||||||
Croatia | Present, Widespread | ||||||
Cyprus | Present | Introduced | 1880 | ||||
Czechia | Present, Widespread | ||||||
Czechoslovakia | Present, Widespread | ||||||
Federal Republic of Yugoslavia | Present, Widespread | ||||||
Denmark | Present | ||||||
Estonia | Present | Introduced | 1850 | ||||
France | Present, Widespread | ||||||
-Corsica | Present | Introduced | 1985 | ||||
Germany | Present, Widespread | ||||||
Greece | Present | ||||||
Hungary | Present, Widespread | ||||||
Ireland | Present | Introduced | 1867 | ||||
Italy | Present, Widespread | ||||||
Latvia | Present | Introduced | 1852 | ||||
Lithuania | Present | Introduced | 1886 | ||||
Netherlands | Present | Introduced | 1825 | ||||
Norway | Present | Introduced | 1875 | ||||
Poland | Present, Widespread | ||||||
Portugal | Present | ||||||
-Azores | Present | Introduced | 1968 | ||||
-Madeira | Present | Introduced | 1914 | ||||
Romania | Present | Introduced | 1816 | ||||
Russia | Present, Widespread | ||||||
Serbia | Present | ||||||
Serbia and Montenegro | Present, Widespread | ||||||
Slovakia | Present | Introduced | 1830 | Invasive | |||
Slovenia | Present | Introduced | 1850 | ||||
Spain | Present, Widespread | ||||||
-Balearic Islands | Present | ||||||
Sweden | Present | Introduced | 1870 | ||||
Switzerland | Present | ||||||
Ukraine | Present | ||||||
United Kingdom | Present | Introduced | 1853 | ||||
North America |
|||||||
Canada | Present, Widespread | ||||||
-Alberta | Present | ||||||
-British Columbia | Present | ||||||
-Manitoba | Present | ||||||
-New Brunswick | Present | ||||||
-Nova Scotia | Present | ||||||
-Ontario | Present | ||||||
-Prince Edward Island | Present | ||||||
-Quebec | Present | ||||||
-Saskatchewan | Present | ||||||
Costa Rica | Present | ||||||
Guatemala | Present, Widespread | ||||||
Mexico | Present, Widespread | ||||||
Puerto Rico | Present | ||||||
United States | Present, Widespread | ||||||
-Alabama | Present | ||||||
-Arizona | Present | ||||||
-Arkansas | Present | ||||||
-California | Present | ||||||
-Colorado | Present | ||||||
-Connecticut | Present | ||||||
-Delaware | Present | ||||||
-Florida | Present | ||||||
-Georgia | Present | ||||||
-Hawaii | Present | ||||||
-Idaho | Present | ||||||
-Illinois | Present, Widespread | ||||||
-Indiana | Present, Widespread | ||||||
-Iowa | Present | ||||||
-Kansas | Present | ||||||
-Kentucky | Present | ||||||
-Louisiana | Present | ||||||
-Maine | Present | ||||||
-Maryland | Present | ||||||
-Massachusetts | Present, Widespread | ||||||
-Michigan | Present, Widespread | ||||||
-Minnesota | Present | ||||||
-Mississippi | Present | ||||||
-Missouri | Present | ||||||
-Montana | Present | ||||||
-Nebraska | Present | ||||||
-Nevada | Present | ||||||
-New Hampshire | Present | ||||||
-New Jersey | Present, Widespread | ||||||
-New Mexico | Present | ||||||
-New York | Present, Widespread | ||||||
-North Carolina | Present | ||||||
-North Dakota | Present | ||||||
-Ohio | Present, Widespread | ||||||
-Oklahoma | Present | ||||||
-Oregon | Present | ||||||
-Pennsylvania | Present, Widespread | ||||||
-Rhode Island | Present, Widespread | ||||||
-South Carolina | Present | ||||||
-South Dakota | Present | ||||||
-Tennessee | Present | ||||||
-Texas | Present | ||||||
-Utah | Present | ||||||
-Vermont | Present | ||||||
-Virginia | Present | ||||||
-Washington | Present | ||||||
-West Virginia | Present | ||||||
-Wisconsin | Present, Widespread | ||||||
-Wyoming | Present | ||||||
Oceania |
|||||||
Australia | Present, Widespread | ||||||
-New South Wales | Present | ||||||
-South Australia | Present | ||||||
-Tasmania | Present | ||||||
-Victoria | Present | ||||||
-Western Australia | Present | ||||||
New Zealand | Present, Widespread | ||||||
South America |
|||||||
Argentina | Present | ||||||
Brazil | Present, Widespread | ||||||
Chile | Present | Introduced | 1849 | ||||
Colombia | Present, Widespread | ||||||
Ecuador | Present, Widespread | ||||||
Peru | Present, Widespread | ||||||
Venezuela | Present |
Habitat
Top of pageHosts/Species Affected
Top of pageHost Plants and Other Plants Affected
Top of pageBiology and Ecology
Top of pageA. retroflexus is an annual that reproduces solely by seed. It is a prolific seed producer, with single vigorous plants capable of producing between 230,000 and 500,000 seeds (Stevens, 1957). Seed production declines beneath crop canopies where light is limited (McLachlan et al., 1995). Germination requirements and dormancy patterns are highly variable depending on distribution and local climatic and ecological conditions and, as such, generalizations should be treated with caution. Recent research suggests that germination is stimulated by light and high temperatures (Gallagher and Cardina, 1997; Oryokot et al., 1997). The seeds are small and most germinate near to the soil surface, with optimum emergence from about 1 cm depth (Wiese and Davis, 1967; Siriwardana and Zimdahl, 1983). Weaver and McWilliams (1980) reported that seeds can remain viable in the soil for many years, but Egley and Chandler (1978) reported a 90% decline in viability after seed burial for 18 months. Seeds are dispersed by wind, animals and as contaminants of crop seeds or farm machinery.
A. retroflexus has the C4 pathway of photosynthesis, typical 'Kranz' leaf anatomy, a low carbon dioxide compensation point and high water use efficiency (Weaver and McWilliams, 1980; Tremmel and Patterson, 1993).
More detailed information on the biology and ecology of A. retroflexus is provided by Weaver and McWilliams (1980) and Holm et al. (1997).
Natural enemies
Top of pageNatural enemy | Type | Life stages | Specificity | References | Biological control in | Biological control on |
---|---|---|---|---|---|---|
Alternaria alternata | Pathogen |
Notes on Natural Enemies
Top of pageImpact
Top of pageA. retroflexus is an alternative host for a number of crop pests and diseases, including the parasitic weed Orobanche ramosa in tomato in the USA, the green peach aphid, Myzus persicae, in orchards, and cucumber mosaic cucumovirus in peppers (Weaver and McWilliams, 1980).
Uses
Top of pageA. retroflexus is palatable to sheep and has a nutrient composition and digestibility equivalent to that of alfalfa (Marten and Andersen, 1975; Moyer and Hironaka, 1993). Closely related Amaranthus species are used as pot herbs, cultivated grains, and ornamental or dye-plants, particularly in Central and South America (Wesche-Ebeling et al., 1995; Mitich, 1997). A. retroflexus is eaten as a vegetable in many places of the world and is used for many food and medicinal uses by Native American groups. A. retroflexus may have traits useful to breeding programmes for the cultivated grain amaranths.
Uses List
Top of pageAnimal feed, fodder, forage
- Fodder/animal feed
Human food and beverage
- Flour/starch
- Seeds
- Vegetable
Materials
- Poisonous to mammals
Medicinal, pharmaceutical
- Traditional/folklore
Similarities to Other Species/Conditions
Top of pageMany other Amaranthus species are superficially similar to A. retroflexus. Of those included in this compendium, A. spinosus has spines, A. viridis has much smaller flowers, A. blitum has indented leaf tips, and A. graecizans and A. blitoides have mainly axillary inflorescences. Further species can occur as weeds on a local basis and reference to local floras or expertise may be necessary
Prevention and Control
Top of pageDue to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.
Control
Cultural Control
Seedlings can be controlled by cultivation, but older plants often recover from mechanical damage and produce axillary inflorescences. Soil solarization under plastic can provide control of A. retroflexus if high temperatures are achieved for prolonged periods of time (Mas and Verdu, 1996).
Chemical Control
A. retroflexus is readily controlled by most herbicides which inhibit photosynthesis, such as atrazine, simazine, metribuzin, linuron and bromoxynil. It is also highly susceptible to the synthetic auxin herbicides, such as 2,4-D or dicamba, and sulfonylurea and imidizolinone herbicides, such as imazethapyr, thifensulfuron-methyl, rimsulfuron and nicosulfuron. Most other herbicides for control of broad-leaved weeds also provide good control including acifluorfen, fomesafen and pendimethalin (Weaver and McWilliams 1980; Bauer et al. 1995; Carey and Kells 1995; Mamarot and Rodriguez, 1997). Its pattern of intermittent germination throughout the growing season, however, makes the application of residual soil-applied herbicides, or sequential post-emergence treatments, necessary in heavily infested fields. A. retroflexus can be controlled by the soil fumigant methyl iodide (Zhang et al., 1997).
Herbicide Resistance
Populations of A. retroflexus resistant to atrazine have been reported in the USA, Canada, France, Germany, Hungary, Switzerland, Spain, Poland, Chile and the Czech Republic (Heap, 1997). Many of these are cross-resistant to metribuzin and linuron (Daban and Garbutt, 1996). Populations resistant to ALS inhibitors (sulfonylureas and imadizolinones) have been reported in the USA and Israel (Heap, 1997). In the past 20 years biotypes resistant to 15 herbicide active ingredients have been reported in 15 countries (LeBaron and Gressel, 1982; Benbrook, 1991).
Biological Control
Biological control of A. retroflexus with fungal pathogens has been reported (Burki et al., 1997). The pigweed flea beetle, Disonycha glabrata, is native to the southern USA and South America. It has been promoted as a control agent of A. retroflexus (Tisler 1990), but it gives incomplete control in the field because beetle populations develop too slowly and too early in the season to prevent competition with the crop and seed production.
References
Top of pageAellen P, Akeroyd JR, 1993. Amaranthus L. In: Tutin TG, Burges NA, Chater AO, Edmondson JR, Heywood VH, Moore DM, Valentine DH, Walters SM, Webb DA, eds. Flora Europaea. Volume 1. Psilotaceae to Platanaceae. 2nd edition. Cambridge, UK: Cambridge University Press, 130-132.
Benbrook C, 1991. Racing against the clock, pesticide resistant biotypes gain ground. Agrichemical Age, 25:30-33.
Brenan JPM, 1961. Amaranthus in Britain. Watsonia, 4:261-280.
Daban ME, Garbutt K, 1996. Herbicide cross-resistance in atrazine-resistant velvetleaf (Abutilon theophrasti) and redroot pigweed (Amaranthus retroflexus). In: Brown H, Cussans GW, Devine MD; Duke SO, Fernandez-Quintanilla C, Helweg A, Labrada RE, Landes M, Kudsk P, Streibig JCP, eds. Proceedings of the Second International Weed Control Congress, Copenhagen, Denmark. Slagelse, Denmark: Department of Weed Control and Pesticide Ecology, 505-510.
Feltner KC, 1970. The ten worst weeds of field crops. 5. Pigweed. Crops and Soils, 23:13-14.
Grant WF, 1959. Cytogenetic studies in Amaranthus. III. Chromosome numbers and phylogenetic aspects. Canadian Journal of Genetics and Cytology, 1:313-328.
Heap IM, 1997. International Survey of Herbicide-Resistant Weeds. Annual Report, Weed Science Society of America.
Holm LG, Doll J, Holm E, Pancho JV, Herberger JP, 1997. World Weeds: Natural Histories and Distribution. New York, USA: John Wiley & Sons Inc.
LeBaron H, Gressel J, 1982. Herbicide Resistance in Plants. New York, USA: John Wiley and Sons.
Mamarot J, Rodriguez A, 1997. Sensibilité des Mauvaises Herbes aux Herbicides. 4th edition. Paris, France: Association de Coordination Technique Agricole.
Mitchell J, Rook A, 1979. Botanical Dermatology: plants and plant products injurious to the skin. Vancouver, Canada: Greengrass.
Mitich LW, 1997. Redroot pigweed (Amaranthus retroflexus). Weed Technology, 11(1):199-202; 35 ref.
Murray MJ, 1940. The genetics of sex determination in the family Amaranthaceae. Genetics, 25:409-431.
Nuss R, Loewus FA, 1978. Further studies on oxalic acid biosynthesis in oxalate-accumulating plants. Plant Physiology, 61:590-592.
Sauer JD, 1955. Revision of the dioecious amaranths. Madrono, 13:5-46.
Sauer JD, 1967. The grain amaranths and their relatives: A revised taxonomic and geographic survey. Annals of the Missouri Botanic Garden, 54:103-137.
Siriwardana T, Zimdahl R, 1983. Competition between barnyard grass (Echinochloa crus-galli) and red-root pigweed (Amaranthus retroflexus). Abstracts of the 23rd Weed Science Society of America Conference, 23:61.
Stevens O, 1957. Weights of seeds and numbers per plant. Weeds, 5:46-55.
USDA, 1970. Selected Weeds of the United States. Agriculture Handbook No. 366. Washington DC, USA: United States Department of Agriculture, 324-325.
Wells MJ, Balsinhas AA, Joffe H, Engelbrecht VM, Harding G, Stirton CH, 1986. A catalogue of problem plants in South Africa. Memoirs of the botanical survey of South Africa No 53. Pretoria, South Africa: Botanical Research Institute.
Wiese A, Davis R, 1967. Weed emergence from two soils at various moistures, temperatures and depths. Weeds, 15:118-121.
Distribution References
Aellen P, Akeroyd JR, 1993. Amaranthus L. In: Flora Europaea. Volume 1. Psilotaceae to Platanaceae, Volume 1 (2nd edition) [ed. by Tutin TG, Burges NA, Chater AO, Edmondson JR, Heywood VH, Moore DM, Valentine DH, Walters SM, Webb DA]. Cambridge, UK: Cambridge University Press. 130-132.
Brenan JPM, 1961. Amaranthus in Britain. In: Watsonia, 4 261-280.
CABI, Undated. CABI Compendium: Status as determined by CABI editor. Wallingford, UK: CABI
USDA, 1970. Selected Weeds of the United States. In: Agriculture Handbook No. 366, Washington DC, USA: United States Department of Agriculture. 324-325.
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