Amaranthus tuberculatus (rough-fruited water-hemp)
- Summary of Invasiveness
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Distribution Table
- History of Introduction and Spread
- Risk of Introduction
- Habitat List
- Hosts/Species Affected
- Growth Stages
- Biology and Ecology
- Latitude/Altitude Ranges
- Air Temperature
- Natural enemies
- Notes on Natural Enemies
- Means of Movement and Dispersal
- Plant Trade
- Impact Summary
- Economic Impact
- Environmental Impact
- Threatened Species
- Social Impact
- Risk and Impact Factors
- Detection and Inspection
- Similarities to Other Species/Conditions
- Prevention and Control
- Gaps in Knowledge/Research Needs
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Amaranthus tuberculatus (Moq.) Sauer
Preferred Common Name
- rough-fruited water-hemp
Other Scientific Names
- Acnida tamariscina var. tuberculata (Moq.) Uline & Bray
- Acnida tuberculata Moq.
- Amaranthus rudis J.D. Sauer
- Amaranthus tuberculatus var. rudis Costea & Tardif
International Common Names
- English: common waterhemp; common water-hemp; roughfruit amaranth; rough-fruit amaranth; tall waterhemp; tall water-hemp
- French: amaranth rugueuse
Local Common Names
- Israel: yarbuz ha’gadot
- Italy: amaranto tubercolato
Summary of InvasivenessTop of page
Amaranthus tuberculatus is an annual dioecious herb 1-2 m tall which has spread from its native range in northern North America and is considered a major weed of agricultural fields and other disturbed areas in 40 US states. In the mid-western USA it has become increasingly difficult to control over the past 10 years due to a persistent seedbank and the development of resistance to certain herbicides. A. tuberculatus seed is a known contaminant of soyabean seed and other grains, and has been accidentally introduced and become naturalized in parts of West Asia and Europe. Potential spread to other areas should be considered likely.
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Plantae
- Phylum: Spermatophyta
- Subphylum: Angiospermae
- Class: Dicotyledonae
- Order: Caryophyllales
- Family: Amaranthaceae
- Genus: Amaranthus
- Species: Amaranthus tuberculatus
Notes on Taxonomy and NomenclatureTop of page
Originally described by Moquin-Tandon (1849) as Acnida tuberculata on the basis of plants cultivated at the Botanical Garden in Geneva (G), Switzerland (“v.v. in hort. Genev.” as reported in the protologue), the lectotype of Amaranthus tuberculatus was only designated in 2015 by Iamonico (2015b) on a specimen preserved at G. The Moquin-Tandon species name was rarely used by subsequent authors. In the 1970s, Sauer (1972) provided the first revision of the dioecious amaranths, and also described the new species Amaranthus rudis, which differed from A. tuberculatus on the basis of some morphological traits, including plant height, tepal number and fruit dehiscence/indehiscence. A more recent study by Pratt and Clark (2001) showed a continuum in the variability of these characters, which led the authors to synonymize the names A. rudis and A. tuberculatus, the latter having nomenclatural priority. Two years later, Costea and Tardif (2003b) proposed varietal rank for A. rudis. Currently, the opinion of Pratt and Clark (2001) is generally accepted (see, for example, Mosyakin and Robertson, 2003; The Plant List, 2013; Iamonico 2015a, 2015c). On the basis of the classification by Mosyakin and Robertson (1996 ), A. tuberculatus belongs to the subgenus Acnida (L.) Aellen ex K.R. Robertson, section Acnida.
DescriptionTop of page
A. tuberculatus is an herb (0.5-)1-2(-3) m tall, dioecious, annual (therophyte). Stems erect or ascending, glabrous, often reddish, branched (rarely simple). Leaves green to reddish, ovate to lanceolate-linear (1.5-)2.0-12.0(-15.0) × (0.5-)0.8-2.5(-3.0) cm, with entire margins, apex obtuse or retuse, mucronulate, base cuneate, glabrous, petioled (petiole 0.5-5.0 cm long). Synflorescences terminal, spike- or panicle-like type (sometimes interrupted-moniliform), erect, usually reddish, the main florescence up to 50 cm long. Floral bracts 1, green to reddish, lanceolate ((0.5-)0.8-2.5(-2.8) × 0.4-1.1(-1.9) mm), as long as or slightly longer than the perianth, sometimes carinate, apex acuminate, margin entire, glabrous. Staminate flowers with 5 tepals, ovate to lanceolate ((1.7-)1.8-3.0(-3.5) × 0.5-1.1(-1.4) mm), apex obtuse or acute, awned (especially the inner tepals); stamens 5. Pistillate flowers without tepals or with only one reduced lanceolate to linear tepal (up to 1.5 mm long); style branches ± erect, stigmas 3. Fruit dark-brown to reddish, subglobose or ellipsoidal ((0.9-)1.2-1.9(-2.3) × 0.9-1.5 mm), as long as or slightly shorter than the perianth, usually smooth, dehiscent. Seed lenticular (0.6-1.0(-1.2) mm in diameter), black or reddish-brown (see Mosyakin and Robertson, 2003) .
DistributionTop of page
It is widely believed that A. tuberculatus is native to northern North America, north of Missouri and Tennessee to the Great Lakes area of the USA and Canada, while the synonymous A. rudis was probably originally native to the Great Plains west of the Mississippi, from Texas to Iowa (Flora of North America Editorial Committee, 2015). The exact native range, however, is unknown with the current state of knowledge, and further studies are needed to clarify this. Indeed, the species is considered as alien in numerous parts of the USA and Canada, although different authorities differ as to which states and provinces the species is native to and into which it has been introduced. A. tuberculatus can definitely be considered as an alien species out of North America; it is currently naturalized and/or invasive in parts of West Asia (Israel and Jordan) and Europe.
Distribution TableTop of page
The 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.
|Continent/Country/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Reference||Notes|
|Israel||Present||Introduced||Danin, 2015; Iamonico, 2015|
|Jordan||Present, few occurrences||Introduced||Castri et al., 1990|
|Canada||Present||Present based on regional distribution.|
|-British Columbia||Present||Introduced||Costea et al., 2005|
|-Manitoba||Present||Introduced||Mosyakin and Robertson, 2003|
|-Ontario||Present||Native||Invasive||Oldham, 2010; Bradley, 2013|
|-Prince Edward Island||Present||Introduced||Mosyakin and Robertson, 2003; USDA-ARS, 2015||Native according to USDA-ARS, 2015|
|-Quebec||Present||Native||Mosyakin and Robertson, 2003|
|USA||Widespread||Native||Invasive||Flora of North America Editorial Committee, 2015|
|-Alabama||Present||Introduced||Mosyakin and Robertson, 2003|
|-Arkansas||Present||Introduced||Mosyakin and Robertson, 2003; USDA-ARS, 2015||Native according to USDA-ARS, 2015|
|-California||Present||Introduced||Hrusa et al., 2002; Mosyakin and Robertson, 2003; Jepson eFlora, 2015|
|-Colorado||Present||Introduced||Mosyakin and Robertson, 2003; Snow and Brasher, 2004|
|-Connecticut||Present||Introduced||Mosyakin and Robertson, 2003; Go Botany, 2015; USDA-ARS, 2015||Native according to USDA-ARS, 2015|
|-Delaware||Present||Introduced||Mosyakin and Robertson, 2003; Flora of Delaware, 2015; USDA-ARS, 2015||Native according to USDA-ARS, 2015|
|-Georgia||Present||Introduced||Mosyakin and Robertson, 2003|
|-Idaho||Present||Introduced||Mosyakin and Robertson, 2003|
|-Illinois||Present||Introduced||Invasive||Mosyakin and Robertson, 2003; USDA-ARS, 2015||Native according to USDA-ARS, 2015|
|-Indiana||Present||Introduced||Invasive||Mosyakin and Robertson, 2003; USDA-ARS, 2015||Native according to USDA-ARS, 2015|
|-Iowa||Present||Native||Invasive||Mosyakin and Robertson, 2003; USDA-ARS, 2015|
|-Kansas||Present||Native||Invasive||Mosyakin and Robertson, 2003; USDA-ARS, 2015|
|-Kentucky||Present||Introduced||Invasive||Mosyakin and Robertson, 2003; Jones, 2005; USDA-ARS, 2015||Native according to USDA-ARS, 2015|
|-Louisiana||Present||Introduced||Mosyakin and Robertson, 2003; USDA-ARS, 2015||Native according to USDA-ARS, 2015|
|-Maine||Present||Introduced||Mosyakin and Robertson, 2003; Go Botany, 2015; USDA-ARS, 2015||Native according to USDA-ARS, 2015|
|-Maryland||Present||Introduced||Mosyakin and Robertson, 2003; USDA-ARS, 2015||Native according to USDA-ARS, 2015|
|-Massachusetts||Present||Introduced||Mosyakin and Robertson, 2003; Cullina et al., 2011; Go Botany, 2015; USDA-ARS, 2015||Native according to USDA-ARS, 2015|
|-Michigan||Present||Introduced||Mosyakin and Robertson, 2003; USDA-ARS, 2015||Native according to USDA-ARS, 2015|
|-Minnesota||Present||Introduced||Mosyakin and Robertson, 2003; USDA-ARS, 2015||Native according to USDA-ARS, 2015|
|-Mississippi||Present||Introduced||Invasive||Mosyakin and Robertson, 2003|
|-Missouri||Present||Native||Invasive||Mosyakin and Robertson, 2003; USDA-ARS, 2015|
|-Nebraska||Present||Introduced||Invasive||Mosyakin and Robertson, 2003; Sarangi et al., 2015; USDA-ARS, 2015||Native according to USDA-ARS, 2015|
|-Nevada||Present||Introduced||Not invasive||Mosyakin and Robertson, 2003|
|-New Hampshire||Present||Introduced||Mosyakin and Robertson, 2003; Go Botany, 2015; USDA-ARS, 2015||Native according to USDA-ARS, 2015|
|-New Jersey||Present||Introduced||Anderson, 2009; Ferren Jr, 2011; USDA-ARS, 2015||Native according to USDA-ARS, 2015|
|-New Mexico||Present||Introduced||Mosyakin and Robertson, 2003|
|-New York||Present||Native||Mosyakin and Robertson, 2003; USDA-ARS, 2015|
|-North Carolina||Present||Introduced||Mosyakin and Robertson, 2003|
|-North Dakota||Present||Introduced||Mosyakin and Robertson, 2003; USDA-ARS, 2015||Native according to USDA-ARS, 2015|
|-Ohio||Present||Introduced||Invasive||Cooperrider et al., 2001; Mosyakin and Robertson, 2003; USDA-ARS, 2015||Native according to USDA-ARS, 2015|
|-Oklahoma||Present||Introduced||Invasive||Buthold, 2013; USDA-ARS, 2015||Native according to USDA-ARS, 2015|
|-Pennsylvania||Present||Introduced||Mosyakin and Robertson, 2003; USDA-ARS, 2015||Native according to USDA-ARS, 2015|
|-South Carolina||Present||Introduced||Mosyakin and Robertson, 2003|
|-South Dakota||Present||Introduced||Mosyakin and Robertson, 2003; USDA-ARS, 2015||Native according to USDA-ARS, 2015|
|-Tennessee||Present||Introduced||Mosyakin and Robertson, 2003; Chester et al., 2009; University of Tennessee Herbarium, 2015; USDA-ARS, 2015||Native according to USDA-ARS, 2015|
|-Texas||Present||Introduced||Mosyakin and Robertson, 2003; Hannick et al., 2013; USDA-ARS, 2015||Native according to USDA-ARS, 2015|
|-Vermont||Localised||Native||Mosyakin and Robertson, 2003; Go Botany, 2015|
|-Virginia||Present||Introduced||Virginia Botanical Associates, 2015||First recorded in Rockingham County in 2012|
|-Washington||Present||Introduced||Mosyakin and Robertson, 2003; Burke Museum of Natural History and Culture, 2015|
|-West Virginia||Present||Introduced||Mosyakin and Robertson, 2003; USDA-ARS, 2015||Native according to USDA-ARS, 2015|
|-Wisconsin||Present||Native||Mosyakin and Robertson, 2003; Flora of Wisconsin, 2015; USDA-ARS, 2015|
|Belgium||Present||Introduced||Not invasive||Iamonico, 2015|
|Czech Republic||Present||Introduced||Iamonico, 2015|
|Denmark||Present||Introduced||Not invasive||Iamonico, 2015|
|Germany||Localised||Introduced||Schmitz, 2002; Iamonico, 2015|
|Netherlands||Localised||Introduced||Not invasive||Meijden et al., 2003|
|Romania||Localised||Introduced||Not invasive||Iamonico, 2015|
|Russian Federation||Present||Introduced||Iamonico, 2015|
|Spain||Localised||Introduced||Sanchez and Verloove, 2013||Observed at Nuevo Puerto, Palos de la Frontera, Huelva|
|Ukraine||Localised||Introduced||Not invasive||Iamonico, 2015|
History of Introduction and SpreadTop of page
Data from microsatellite marker studies by Waselkov and Olsen (2014), which identified two genetic lineages for A. tuberculatus, suggested that an eastward movement of the western genetic lineage (identified by some as var. rudis) is the source of the agricultural invasion of water-hemp seen in the USA today. Spread of the weed has been facilitated by changing farming practices, such as the increased sowing of maize and soyabean monocultures and adoption of reduced or no-tillage systems. From the USA, the weed (var. rudis) has recently spread to Canada where it was found in soyabean crops in south-western Ontario in 2002 and 2003, although the var. tuberculatus form has been known in Ontario and Quebec from the end of the 19th century (Costea et al., 2005). Contamination of soyabean shipments has been a major means by which water-hemp has become established in Europe. In Belgium, for example, since 1983 A. tuberculatus has been found in port areas (Antwerp, Gent), near grain conveyors and mills, on quaysides and along roadside verges. Since 2003, it has spread along gravelly riverbanks in Belgium and the Netherlands (Manual of the Alien Plants of Belgium, 2015). Sanchez Gullon and Verloove (2013) report A. tuberculatus for the first time in Spain at the port in Palos de la Frontera.
Risk of IntroductionTop of page
Contaminated soyabean and other grain shipments remain a major risk factor in the invasion of new areas by A. tuberculatus. In Europe, first reports tend to occur in the vicinity of ports. Once introduced, it appears to thrive along water courses and rivers, its high reproductive capacity allowing it to spread rapidly with resulting adverse ecological effects on the native riparian herbaceous vegetation, for example along the banks of the River Po in Italy (Iamonico 2015c).
HabitatTop of page
A. tuberculatus occurs naturally in North America on the margins of freshwater bodies, rivers, lakes, ponds, marshes and bogs, while preferred human-made habitats are roadsides, railroads, cultivated fields, waste land and gardens (Mosyakin and Robertson, 2003, Iamonico, 2015c).
Habitat ListTop of page
|Terrestrial – Managed||Cultivated / agricultural land||Principal habitat||Harmful (pest or invasive)|
|Cultivated / agricultural land||Principal habitat||Natural|
|Disturbed areas||Principal habitat||Harmful (pest or invasive)|
|Disturbed areas||Principal habitat||Natural|
|Rail / roadsides||Secondary/tolerated habitat||Harmful (pest or invasive)|
|Rail / roadsides||Secondary/tolerated habitat||Natural|
|Urban / peri-urban areas||Secondary/tolerated habitat||Harmful (pest or invasive)|
|Urban / peri-urban areas||Secondary/tolerated habitat||Natural|
|Terrestrial ‑ Natural / Semi-natural||Riverbanks||Principal habitat||Harmful (pest or invasive)|
|Wetlands||Principal habitat||Harmful (pest or invasive)|
Hosts/Species AffectedTop of page
A. tuberculatus negatively affects the growth and yield of cultivated crops. Estimated soyabean yield losses due to the presence of dense populations of A. tuberculatus (89-360 plants/m2) that emerged at the crop unifoliate stage have been high; for example, yield reductions of 43% in Illinois and 27-63% in Kansas have been reported (Hager et al., 2002; Bensch et al., 2003). In maize crops in Illinois, season-long interference from dense populations of A. tuberculatus (60-300 plants/m2) reduced yield by up to 74% (Steckel and Sprague, 2004).
Growth StagesTop of page Post-harvest, Seedling stage, Vegetative growing stage
Biology and EcologyTop of page
A. tuberculatus is a diploid taxon with a chromosome number of 2n = 32 (Trucco et al. 2006). The species can hybridize in the wild with other members of the subgenus Acnida and even with monoecious species belonging to subgenus Amaranthus, such as A. hybridus (Costea et al., 2005; Trucco et al., 2004, 2005).
Throughout the mid-western USA, A. tuberculatus populations have since the early 1990s developed genetic resistance to herbicides inhibiting photosystem II (e.g., triazines), acetolactate synthase (ALS) (e.g., sulfonylureas) and protoporphyrinogen oxidase (PPO) (e.g., diphenylethers) (Heap, 2004). The first report of resistance was to triazine herbicides in Nebraska in 1990 (Anderson et al., 1996), and has since then been discovered, along with resistance to other herbicides, in numerous US states as well as Ontario, Canada. Cases of multiple resistance to triazines, ALS or PPO inhibitors have also been reported (Heap, 2004; Patzoldt et al., 2005). Genetic variation within and between populations in response to various herbicides (Patzoldt et al., 2003), as well as interspecific hybridization and gene flow between species (Wetzel et al. 1999; Franssen et al. 2001b), have probably contributed to the rapid spread of herbicide resistance in Amaranthus species.
A. tuberculatus is a summer annual herb (therophyte). Flower initiation depends on photoperiod. Under short-day conditions (8 hours) flowering starts after 14–16 days, while under long-day conditions (16 hours) it starts at about 45 days. Pollination is mediated by wind, the pollen having numerous and uniformly distributed apertures which generate a layer of turbulent air to decrease the friction between the pollen grain and the air, thus maximizing the distance pollen grains can be wind-dispersed (Franssen et al., 2001a, Costea et al., 2005). Each plant produces a high number of viable seeds. Seedlings emerge and grow rapidly.
Physiology and Phenology
A. tuberculatus, like all Amaranthus species, is a C4 photosynthetic pathway species, exhibiting the characteristic Kranz leaf anatomy and high photosynthetic rate at high temperatures and light intensities, with reduced photorespiration and a low CO2 compensation point compared to C3 species (Costea et al., 2004). Flowering time is from late May to August in its native distribution area, and can be from September to October in some non-native areas (e.g., in Europe).
In Canada, frequently associated plant species are Chenopodium album, A. retroflexus, A. powellii and Polygonum persicaria [Persicaria maculosa], while in the USA (Iowa) in soyabean and maize crops not treated with herbicides, associated weed species include Ambrosia artemisiifolia, Asclepias syriaca, C. album, Erigeron sumatrensis [Conyza sumatrensis], Cyperus esculentus, Hibiscus trionum, Setaria faberi, S. glauca [Setaria pumila], Sida spinosa, Solanum carolinense, S. ptycanthum and Polygonum pensylvanicum [Persicaria pensylvanica] (Felix and Owen, 1999; Costea et al., 2005).
Although a temperate species, A. tuberculatus occurs over a wide climate range. It can tolerate a broad range of soil types and textures, but prefers those that are well-drained and rich in nutrients. A soil pH from 4.5 to 8 is suitable. Plants can tolerate temporary flooding, but have no salinity tolerance. CaCO3 tolerance is said to be moderate (USDA-NRCS, 2015).
ClimateTop of page
|Cf - Warm temperate climate, wet all year||Tolerated||Warm average temp. > 10°C, Cold average temp. > 0°C, wet all year|
|Cs - Warm temperate climate with dry summer||Preferred||Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers|
|Ds - Continental climate with dry summer||Preferred||Continental climate with dry summer (Warm average temp. > 10°C, coldest month < 0°C, dry summers)|
Latitude/Altitude RangesTop of page
|Latitude North (°N)||Latitude South (°S)||Altitude Lower (m)||Altitude Upper (m)|
Air TemperatureTop of page
|Parameter||Lower limit||Upper limit|
|Mean minimum temperature of coldest month (ºC)||-3||0|
Natural enemiesTop of page
|Natural enemy||Type||Life stages||Specificity||References||Biological control in||Biological control on|
|Albugo bliti||Pathogen||Leaves||not specific|
|Amara aeneopolita||Herbivore||Seeds||not specific|
|Anisodactylus rusticus||Herbivore||Seeds||not specific|
|Cercospora acnidae||Pathogen||Leaves||not specific|
|Gryllus pennsylvanicus||Herbivore||Seeds||not specific||N/A||N/A|
|Harpalus pensylvanicus||Herbivore||Seeds||not specific|
|Microsphaeropsis amaranthi||Pathogen||Leaves/Stems||not specific||Smith et al., 2006||USA|
|Phyllosticta amaranthi||Pathogen||Leaves||not specific|
|Phymatotrichopsis omnivora||Pathogen||Roots||not specific|
|Stenolophus comma||Herbivore||Seeds||not specific||N/A||N/A|
Notes on Natural EnemiesTop of page
In the USA (Iowa), the most important post-dispersal seed predators observed were Amara aeneopolita, Anisodactylus rusticus, Stenolophus comma, Gryllus pennsylvanicus and Harpalus pensylvanicus.
Fungi found infecting A. tuberculatus in the USA have included Albugo bliti [Wilsoniana bliti], Phymatotrichum omnivorum [Phymatotrichopsis omnivora], Cercospora acnidae and Phyllosticta amaranthi. Microsphaeropsis amaranthi has been tested as a possible biocontrol agent. There appear to be no data on bacteria, viruses or parasites (Costea et al., 2005).
Means of Movement and DispersalTop of page
The morphology of the seeds facilitates dispersal by water, animals and birds, and to a lesser extent wind, with dispersal by water (streamlets produced on the soil by rain, surface irrigation and rivers) being of particular significance as both fruits and seeds float, and plants prefer to grow in the proximity of water (Costea et al., 2005).
Vector Transmission (Biotic)
Seeds of A. tuberculatus are also dispersed by animals and birds, although there is no evidence of ingestion and subsequent excretion by livestock (Costea et al., 2005).
Anthropogenic factors such as farm machinery, and manure and compost spreading also aid dispersal of A. tuberculatus seed within and between fields, while transport of contaminated soyabean seed and other grains aids local and long-distance dispersal through accidental spillages (Costea et al., 2005; Manual of the Alien Plants of Belgium, 2015).
Plant TradeTop of page
|Plant parts liable to carry the pest in trade/transport||Pest stages||Borne internally||Borne externally||Visibility of pest or symptoms|
|True seeds (inc. grain)||Yes|
|Plant parts not known to carry the pest in trade/transport|
|Fruits (inc. pods)|
|Growing medium accompanying plants|
|Stems (above ground)/Shoots/Trunks/Branches|
Impact SummaryTop of page
Economic ImpactTop of page
A. tuberculatus successfully outcompetes cultivated plants both in its native range and where introduced and naturalized. By reducing crop yields by as much as 63% for soyabeans (Hager et al., 2002; Bensch et al., 2003) and 74% for maize (Steckel and Sprague, 2004), the weed can substantially reduce farm incomes. Inattention by farmers to the situation with A. tuberculatus in their fields, as with other Amaranthus species, can help the weed become more established and more troublesome (Costea et al., 2001a; Iamonico, 2010b).
Already a noxious weed, A. tuberculatus populations have since the 1990s been found exhibiting resistance to triazines and ALS- and PPO-inhibiting herbicides, as well as glyphosate, thus further impacting on crop yields and the costs of crop production, and requiring not only the development and use of other, newer herbicides, but also changes to weed management strategies and agricultural practices to reduce the risk of herbicide resistance development and spread (Tranel et al., 2011).
Environmental ImpactTop of page
Increases in alien invasive weed population densities cause modifications in the structure of native vegetation communities by, for example, changing the frequency and coverage of native species (α-biodiversity) through high and positive competition for nutrients and space. A. tuberculatus can therefore be a threat to native riparian herbaceous vegetation, especially in territories outside its native range. In the River Po area of northern Italy, for example, the spread of alien species (Rossi et al., 2013), such as A. tuberculatus, threatens the endangered species Myricaria germanica (Alessandrini et al., 2013), Typha minima, Sagittaria sagittifolia and Hippuris vulgaris, and the near-threatened Typha shuttleworthii and Epipactis palustris, as well as Lindernia palustris (Iamonico, pers. obs., 2015).
Another potential unfavourable impact on biodiversity is the capacity of A. tuberculatus to hybridize with other Amaranthus species, thus negatively affecting the gene pools of those species.
Threatened SpeciesTop of page
|Threatened Species||Conservation Status||Where Threatened||Mechanism||References||Notes|
|Epipactis palustris||NT (IUCN red list: Near threatened) NT (IUCN red list: Near threatened)||Italy||Competition - monopolizing resources|
|Hippuris vulgaris||No Details||Italy||Competition - monopolizing resources|
|Lindernia palustris||No Details||Italy||Competition - monopolizing resources|
|Myricaria germanica||EN (IUCN red list: Endangered) EN (IUCN red list: Endangered); No details No details||Italy||Competition - monopolizing resources|
|Sagittaria sagittifolia||No Details||Italy||Competition - monopolizing resources|
|Typha minima||No Details||Italy||Competition - monopolizing resources|
|Typha shuttleworthii||No Details||Italy||Competition - monopolizing resources|
Social ImpactTop of page
The high number of flowers and pollen grains produced by each plant, as well as the reduced sizes and types of pollen in the genus Amaranthus as a whole (Costea et al. 2001b, 2005; Costea and Tardif, 2003; Iamonico 2010), would indicate that A. tuberculatus is a potentially allergenic species.
Risk and Impact FactorsTop of page Invasiveness
- Invasive in its native range
- Proved invasive outside its native range
- Has a broad native range
- Abundant in its native range
- Highly adaptable to different environments
- Is a habitat generalist
- Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
- Pioneering in disturbed areas
- Highly mobile locally
- Benefits from human association (i.e. it is a human commensal)
- Fast growing
- Has high reproductive potential
- Has high genetic variability
- Changed gene pool/ selective loss of genotypes
- Ecosystem change/ habitat alteration
- Increases vulnerability to invasions
- Modification of nutrient regime
- Modification of successional patterns
- Negatively impacts agriculture
- Negatively impacts human health
- Negatively impacts livelihoods
- Reduced native biodiversity
- Threat to/ loss of endangered species
- Threat to/ loss of native species
- Damages animal/plant products
- Causes allergic responses
- Competition - monopolizing resources
- Competition - shading
- Rapid growth
- Highly likely to be transported internationally accidentally
- Difficult/costly to control
UsesTop of page
There appear to be no significant human uses of A. tuberculatus from any economic, social or environmental point of view. As with other amaranths, A. tuberculatus has the potential of being used as a leaf vegetable.
DiagnosisTop of page
No laboratory techniques appear to be available for testing and screening.
Detection and InspectionTop of page
Although no specific research into detection methods appears to have been carried out for A. tuberculatus, detection can be carried out by careful and continuous floristic surveys during the seasons, especially around ports handling soyabean and grain shipments.
Similarities to Other Species/ConditionsTop of page
A. tamariscinus Nutt. is a similar and related species which was considered a synonym of A. tuberculatus by some authors. On the basis of an examination of Nuttall's collection, Sauer (1972) stated that the name A. tamariscinus refers to a sterile hybrid between A. tuberculatus and a monoecious taxon, possibly A. hybridus. Recently, Iamonico (2010a) clarified the identity of A. tamariscinus, confirming its hybrid origin. The two species differ by the number and length of the tepals: absent or sometimes a single tepal ≤ 1.5 mm long in A. tuberculatus, while A. tamariscinus has 2 tepals, one of them ≤ 1 mm long.
With regard to the other weedy Amaranthus species present in North America, A. tuberculatus can be distinguished by its long, narrow leaves and by the lack of hairs on its stems and leaves, giving the plant a very glossy appearance (Gower and Lee, 2001).
Prevention and ControlTop of page
Due 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.
It should be possible to reduce or manage the impact of A. tuberculatus invasions if quick action is taken to identify and map the foci of infestations, determine population dynamics under the prevailing climatic conditions and establish proper methods of control and management.
Cultural Control and Sanitary Measures
As the hypocotyl of A. tuberculatus can only elongate 0.5-3.5(-5) cm, most seedlings emerge from near the soil surface. This being the case, no-tillage or reduced-tillage cropping systems should be avoided, and deep mouldboard ploughing to bury seeds should be practised. Interrow cultivation can also reduce weed survival and seed return (Buhler et al., 2001). Thorough cleaning of combine harvesters before moving equipment to other fields would limit the transport of seeds (Costea et al., 2005).
Microsphaeropsis amaranthi infecting A. tuberculatus causes foliar and stem necrosis, resulting in plant mortality under optimal conditions. Preliminary testing in the Midwestern USA concluded that its efficacy as a bioherbicide, however, was limited under field conditions (Smith et al., 2006).
Foliar-applied herbicides will control growing A. tuberculatus weeds. Tested pre-emergence herbicides include sulfentrazone (Krausz and Young, 2003), flumioxazin, S-metolachlor, pendimethalin, acetochlor, linuron, imazethapyr, metribuzin, flufenacet plus metribuzin, flumetsulam plus metolachlor, isoxaflutole and mesotrione (Sweat et al. 1998, Niekamp and Johnson 2001, Steckel et al. 2002). Post-emergence herbicides which have proved effective include lactofen and fomesafen (Hager et al. 2003).
Gaps in Knowledge/Research NeedsTop of page
Further research is required in the following areas:
Molecular taxonomical analyses of native and alien populations.
Phytosociological studies in the USA and non-native areas in which A. tuberculatus appears to be invasive.
Detailed study of the chorology of A. tuberculatus in its native and introduced ranges.
Investigations of its invasiveness through studies of the history of introduction (examination of herbaria specimens), substratum characteristics, pollination, pollen morphology, and seed production, dispersal and germination.
ReferencesTop of page
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ContributorsTop of page
30/05/2015 Original text by:
Duilio Iamonico, Consultant, Rome, Italy.
Distribution MapsTop of page
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