Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide


Ambrosia psilostachya
(perennial ragweed)



Ambrosia psilostachya (perennial ragweed)


  • Last modified
  • 14 November 2018
  • Datasheet Type(s)
  • Invasive Species
  • Pest
  • Host Plant
  • Preferred Scientific Name
  • Ambrosia psilostachya
  • Preferred Common Name
  • perennial ragweed
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Plantae
  •     Phylum: Spermatophyta
  •       Subphylum: Angiospermae
  •         Class: Dicotyledonae
  • Summary of Invasiveness
  • The further movement of A. psilostachya to new regions is possible as a seed contaminant in cereal grain. Through its spreading rootstocks, an area can be quickly colonized by one or a few original plants, despite low seed production, and control is...

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Infestation of A. psilostachya.
CaptionInfestation of A. psilostachya.
CopyrightDepartment of Natural Resources, Mines & Energy
Infestation of A. psilostachya.
HabitInfestation of A. psilostachya.Department of Natural Resources, Mines & Energy
Leaves of A. psilostachya.
CaptionLeaves of A. psilostachya.
CopyrightDepartment of Natural Resources, Mines & Energy
Leaves of A. psilostachya.
LeavesLeaves of A. psilostachya.Department of Natural Resources, Mines & Energy
Flowers of A. psilostachya.
CaptionFlowers of A. psilostachya.
CopyrightDepartment of Natural Resources, Mines & Energy
Flowers of A. psilostachya.
FlowersFlowers of A. psilostachya.Department of Natural Resources, Mines & Energy


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Preferred Scientific Name

  • Ambrosia psilostachya DC.

Preferred Common Name

  • perennial ragweed

Other Scientific Names

  • Ambrosia californica Rydb.
  • Ambrosia coronopifolia Torr. & A. Gray
  • Ambrosia cumanensis auct. non Kunth
  • Ambrosia glandulosa Scheele
  • Ambrosia hispida Torr.
  • Ambrosia lindheimeriana Scheele
  • Ambrosia maritima L.
  • Ambrosia psilostachya var. coronopifolia Torr. & A. Gray
  • Ambrosia rugelii Rydb.

International Common Names

  • English: western ragweed
  • Spanish: artemisa perenne
  • French: l'herbe á poux vivace
  • Russian: ambrosia mnogoletnyaya

Local Common Names

  • Germany: Ausdauernde Ambrosie; Stauden- Ambrosie
  • Poland: ambrozji zachodnie
  • USA: cuman ragweed

EPPO code

  • AMBCU (Ambrosia cumanensis)
  • AMBMA (Ambrosia maritima)
  • AMBPC (Ambrosia psilostachya var. coronopifolia)
  • AMBPS (Ambrosia psilostachya)

Summary of Invasiveness

Top of page The further movement of A. psilostachya to new regions is possible as a seed contaminant in cereal grain. Through its spreading rootstocks, an area can be quickly colonized by one or a few original plants, despite low seed production, and control is not easy. A. psilostachya is highly competitive and will invade crops and pastures. Negative impacts include: crop losses, decrease in fodder availability, reduction in the local flora and increased human allergic reactions.

Taxonomic Tree

Top of page
  • Domain: Eukaryota
  •     Kingdom: Plantae
  •         Phylum: Spermatophyta
  •             Subphylum: Angiospermae
  •                 Class: Dicotyledonae
  •                     Order: Asterales
  •                         Family: Asteraceae
  •                             Genus: Ambrosia
  •                                 Species: Ambrosia psilostachya

Notes on Taxonomy and Nomenclature

Top of page The name Ambrosia means food of the gods (Spencer, 1957). Payne (1970) has listed 11 scientific names including species, subspecies and varieties which he refers to synonymously under Ambrosia psilostachya DC. Of these, only A. coronopifolia T. & G. and A. psilostachya DC. var. coronopifolia (T. & G.) Farwell are frequently used (Bassett and Crompton, 1975). Wagner and Beals (1958) have tentatively treated A. coronopifolia T. & G. and A. psilostachya DC. as two distinct species. They found that these taxa differ from each other in habit, pubescence, distribution, and shape of fruit, pollen size, and other characters. Typical A. psilostachya apparently grows only in the southern portion of the USA while the sole perennial species in the central states is A. coronopifolia. The pollen of A. psilostachya was observed to be larger than that of A. coronopifolia. All the Canadian material examined is A. coronopifolia (A. psilostachya var. coronopifolia (T. & G.) Farw.). The morphological variability of A. psilostachya is probably related, at least in part, to the presence in this species of a polyploid series (Bassett and Crompton, 1975), and A. coronocopia is treated here as a synonym of A. psilostachya. The accepted common name is perennial ragweed.


Top of page A psilostachya is an erect perennial broadleaved weed, spreading by seeds and rhizomes. The stems are unbranched or branched, harshly pubescent with stiff, short, minutely glandular hairs. It grows from 30 to 105 cm tall. Leaves are 5-10 cm long, opposite at the base, alternate above, hairy, pinnately to bi-pinnately lobed, thickish, light green to greyish green, subsessile or occasionally on short-winged petioles. Flower heads contain either male or female flowers and are on different parts of the same plant. Flowers are produced from summer to early autumn (July to October). Staminate (male) flowers numbering 10 to 40 per plant are yellowish-white and stalked to subsessile, arranged in spikes terminating the stems and branchlets. The involucre is hirsutulous with usually tuberculate-based hairs; corolla five-lobed (Bassett and Crompton, 1975). Male flowers produce excessive wind-dispersed pollen. Pistillate (female) heads 1-flowered, sessile, single or clustered in the upper axils. The fruits are obovate achenes, greenish-brown, grey or dark grey, 2.5-3(-6) mm long and 2-3.5 mm broad with a short blunt spine. Seeds are obovate, approximately 2-3 mm long and1.8-2.5 mm broad, smooth and shiny.


Top of page A. psilostachya is a native of North America and originated in western USA (Rydberg, 1965; Bassett and Crompton, 1975; Lorenzi and Jeffery, 1987). In Canada, the area of greatest concentration of the perennial ragweed lies in southeastern Saskatchewan and southern Manitoba and is rare in British Columbia, Alberta, Ontario and the rest of eastern Canada (Bassett and Crompton, 1975). Outside North America the perennial ragweed has been introduced to many countries in Europe (Lawalrée, 1947), Asia (Kazakhstan) (Buyankin, 1975), Africa (Mauritius) (McIntyre, 1985) and Australia (Eardley, 1944; Auld and Medd, 1987).

Distribution Table

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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/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes


IndiaPresentPresent based on regional distribution.
-KarnatakaPresentPrasad et al., 2013
KazakhstanRestricted distributionIntroduced Invasive Buyankin, 1975


MauritiusPresentMcIntyre, 1985

North America

CanadaRestricted distributionIntroduced1885 Invasive Bassett and Terasmae, 1962; Bassett and Crompton, 1975
-AlbertaRestricted distributionIntroduced Invasive Bassett and Terasmae, 1962; Bassett and Crompton, 1975
-British ColumbiaRestricted distributionIntroduced1885 Invasive Bassett and Terasmae, 1962; Bassett and Crompton, 1975
-ManitobaWidespreadIntroduced Invasive Bassett and Terasmae, 1962; Bassett and Crompton, 1975
-OntarioRestricted distributionIntroduced Invasive Bassett and Terasmae, 1962; Bassett and Crompton, 1975
-QuebecPresentIntroduced Invasive Bassett and Terasmae, 1962; Bassett and Crompton, 1975
-SaskatchewanWidespreadIntroduced Invasive Bassett and Terasmae, 1962; Bassett and Crompton, 1975
MexicoPresentNativeUSDA-ARS, 2003
USAWidespreadNativeBritton and Brown, 1936; Rydberg, 1965
-AlabamaPresentNativeUSDA-NRCS, 2002
-ArizonaWidespreadNativeBritton and Brown, 1936
-ArkansasPresentNativeUSDA-NRCS, 2002
-CaliforniaWidespreadNativeBritton & Brown, 1965; Britton & Brown, Rydberg; Britton and Brown, 1936
-ColoradoWidespreadNativeBritton and Brown, 1936
-ConnecticutWidespreadNativeBritton and Brown, 1936
-FloridaPresentNativeUSDA-NRCS, 2002
-GeorgiaPresentNativeUSDA-NRCS, 2002
-IdahoWidespreadNative Invasive Britton and Brown, 1936; USDA-NRCS, 2002
-IllinoisWidespreadNativeBritton and Brown, 1936
-IndianaWidespreadNativeBritton and Brown, 1936
-IowaWidespreadNativeBritton and Brown, 1936
-KansasWidespreadNativeBritton and Brown, 1936
-LouisianaPresentNativeUSDA-NRCS, 2002
-MaineWidespreadNativeBritton and Brown, 1936
-MassachusettsWidespreadNativeBritton and Brown, 1936
-MichiganWidespreadNativeBritton and Brown, 1936
-MinnesotaWidespreadNativeBritton and Brown, 1936
-MissouriWidespreadNativeBritton and Brown, 1936
-MontanaWidespreadNativeBritton and Brown, 1936
-NebraskaWidespreadNativeBritton and Brown, 1936
-NevadaWidespreadNativeBritton and Brown, 1936
-New HampshireWidespreadNativeBritton and Brown, 1936
-New MexicoWidespreadNativeBritton and Brown, 1936
-New YorkWidespreadNativeBritton and Brown, 1936
-North DakotaWidespreadNativeBritton and Brown, 1936
-OhioPresentNativeUSDA-NRCS, 2002
-OklahomaWidespreadNativeBritton and Brown, 1936
-OregonPresentNativeUSDA-NRCS, 2002
-PennsylvaniaPresentNativeUSDA-NRCS, 2002
-South CarolinaPresentNativeUSDA-NRCS, 2002
-South DakotaWidespreadNativeBritton and Brown, 1936
-TennesseePresentNativeUSDA-NRCS, 2002
-TexasWidespreadNativeBritton and Brown, 1936
-UtahWidespreadNativeBritton and Brown, 1936
-VermontPresentNativeUSDA-NRCS, 2002
-WashingtonPresentNative Invasive USDA-NRCS, 2002
-WisconsinWidespreadNativeBritton and Brown, 1936
-WyomingWidespreadNative Invasive Britton and Brown, 1936; USDA-NRCS, 2002


BelgiumPresentIntroduced Invasive Lawalrée, 1947; Tutin et al., 1976
HungaryPresentIntroduced Invasive Lawalrée, 1947; Tutin et al., 1976
ItalyPresentIntroduced Invasive Lawalrée, 1947; Tutin et al., 1976
NetherlandsPresentIntroduced Invasive Tutin et al., 1976
PolandRestricted distributionIntroduced Invasive Tutin et al., 1976; Karnkowski, 2001
Russian FederationRestricted distributionIntroduced Invasive Moskalenko, 2001; EPPO, 2014
-Central RussiaRestricted distributionEPPO, 2014
-Southern RussiaRestricted distributionIntroduced Invasive Moskalenko, 2001; EPPO, 2014
SpainPresentIntroduced Invasive Lawalrée, 1947; Tutin et al., 1976
SwedenPresentIntroduced Invasive Lawalrée, 1947; Tutin et al., 1976


AustraliaPresentIntroduced Invasive Eardley, 1944; Auld and Medd, 1987
-New South WalesPresentIntroduced Invasive Auld and Medd, 1987; Royal Botanic Gardens Sydney, 2003
-QueenslandPresentIntroducedAuld and Medd, 1987
-VictoriaPresentIntroduced Invasive Auld and Medd, 1987; Royal Botanic Gardens Sydney, 2003
-Western AustraliaPresentIntroduced Invasive Royal Botanic Gardens Sydney, 2003

History of Introduction and Spread

Top of page A. psilostachya was introduced into British Columbia, Canada probably as early as 1885. It then migrated from the south-west into eastern Canada (Bassett and Terasmae, 1962). The first record of A. psilostachya in Russia was from Krasnodar region, Southern Russia in 1945 (Anon., 1970) and by 1960 was found in 6 regions of Russia: Krasnodar, Stavropol, Samara, Volgograd, Bashkortostan and Kalmikiya. In 1969, A. psilostachya infested 1761 ha in Russia and was found for the first time in Orenburg region. Quarantine measures limited weed distribution, and now the area occupied by A. psilostachya is about 1160 ha (Moskalenko, 2001). In Kazakhstan, A. psilostachya was found for the first time in 1970 and by 1975 was classed as invasive (Buyankin, 1975).

Risk of Introduction

Top of page A. psilostachya was listed in the noxious weed act of Manitoba, Ontario and Saskatchewan (Bassett and Crompton, 1975), listed as a noxious weed by three states of the USA (USDA-NRCS, 2002), and is declared a class C noxious weed in the Northern Territory, Australia (Crothers, 1993). Ambrosia spp. seem to possess the highest potential phytosanitary risk in Poland (Karnkowski, 2001) and in Russia, A. psilostachya is listed as a quarantine weed. Quarantine phytosanitary measures limited weed distribution (Moskalenko, 2001), but there remains a high risk that this species will be further introduced as a seed contaminant of cereal grain.


Top of page A. psilostachya forms large populations along roadsides, railways embankments, in abandoned fields, wastelands, open prairies, orchards and in cultivated agronomic and horticultural crops. A. psilostachya will invade grassy fields (Bassett and Terasmae, 1962; Bassett and Crompton, 1975; Moskalenko, 2001) and thrives in disturbed sites (Wagner and Beales, 1958).

Habitat List

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Terrestrial – ManagedCultivated / agricultural land Present, no further details Harmful (pest or invasive)
Managed forests, plantations and orchards Present, no further details Harmful (pest or invasive)
Managed grasslands (grazing systems) Present, no further details Harmful (pest or invasive)
Disturbed areas Present, no further details Harmful (pest or invasive)
Rail / roadsides Present, no further details Harmful (pest or invasive)
Urban / peri-urban areas Present, no further details Harmful (pest or invasive)
Terrestrial ‑ Natural / Semi-naturalNatural forests Present, no further details
Natural grasslands Present, no further details Harmful (pest or invasive)
Riverbanks Present, no further details

Hosts/Species Affected

Top of page A. psilostachya is an aggressive and competitive weed of agriculture and pastures. The plants of perennial ragweed inhibit germination and early seedling growth of different crops, notably rye, wheat, oat, tomato and alfalfa (Dalrymple and Rogers, 1983). A. psilostachya can compete with perennial grasses on artificial pastures and native ranges (Vermeire and Gillen, 2000).

Growth Stages

Top of page Post-harvest, Pre-emergence, Seedling stage, Vegetative growing stage

Biology and Ecology

Top of page Genetics

The chromosome number of 2n=72 for A. psilostachya was reported from Ontario, Canada and Michigan, USA (Mulligan, 1957; Wagner and Beals, 1958). However, Payne et al. (1964) reported chromosome counts for A. psilostachya of 2n=36, 54 and 72, whereas Miller et al (1968) found different populations of A. psilostachya were all diploid (n=18, 2n=36). Payne (1970) reported no correlation between ploidy levels and morphological expressions of A. psilostachya. The hybrid Ambrosia artemisiifolia x A. psilostachya (A. intergradiens Wagner) has been found in USA (Wagner and Beals, 1958). This hybrid often formed clonal populations that persisted for many years but it is not known whether viable seeds are produced in these patches. Somatic chromosome counts from three localities of this hybrid were 2n=54.

Physiology and Phenology

A. psilostachya survives and spreads primarily by spreading rootstocks. The growth of the shoots begins in May (Bassett and Crompton, 1975; Moskalenko, 2001). Vermeire and Gillen (2000) found that survival of A. psilostachya shoots from June to September was greater in mixed prairie (81%) than in tallgrass prairie (63%) and was greater in ungrazed (76%) than grazed plots (68%). A. psilostachya shoots weighed less per unit height in tallgrass prairie, and shoots in ungrazed plots were taller than shoots in grazed plots but weighed less per unit height. These differences in shoot morphology are consistent with increased competition for light in tallgrass prairie and in ungrazed sites. The frequency of A. psilostachya increased on grazed areas (Berg et al., 1997). A. psilostachya can grow from rhizomes 5 cm long. Under glasshouse conditions shoot regeneration from 2-5 cm soil depth was better than from 10-15 cm deep but plants which emerged from the deeper soil layer had the highest shoot and root fresh weights (Miziniak and Praczyk, 2002). Warming increased A. psilostachya stems by 88% when not clipped and 46% when clipped. Clipping increased ragweed stems by 75 and 36% in the control and warmed plots, respectively. Dry mass per A. psilostachya stem in the warmed plots was 38% greater than that in the control plots. Although warming caused no difference in pollen production per stem, total pollen production increased by 84% because there were more A. psilostachya stems (Wan et al., 2002). Flowering occurs in July, and mature seeds form at the end of August or early September (Bassett and Crompton, 1975; Moskalenko, 2001). Seeds contained an average of 13% crude protein and 21% fat (Peoples et al., 1994).

Reproductive Biology

Through its spreading rootstocks, an area can be readily colonized by one or a few original plants despite the small seed set. The reproductive strategy appears similar in all habitats. In the first year, the individual plant does not appear to produce additional shoots from its root system. In the second year, new shoots emerge from the creeping rootstocks thus establishing a clone which can cover about 2 m² (Wagner and Beals, 1958). A. psilostachya is primarily anemophilous (wind-pollinated). It does shed large quantities of air-borne pollen that causes hay fever symptoms (Wodehouse, 1971; Bassett and Crompton, 1975). The plant produces one seed per flowering head. Wagner and Beals (1958) counted a total of 118 flowering heads on one plant from which only 66 fruits developed to maturity. Since reproduction takes place largely by vegetative means, seed production in this plant is of secondary importance to its survival and spread. Seeds have no germination at maturity and usually require winter stratification before germination. The optimal temperatures for seed germination are 18-22°C (Moskalenko, 2001). Seeds are able to germinate both in darkness and light, but light seems to promote germination. Seeds on the soil surface lose their viability after four years, but those in deeper soil layers keep their viability for longer (Beres, 2003).

Environmental Requirements

Allard (1943) states that all Ambrosia spp. are most common between latitudes 45° and 30° in both the northern and southern hemispheres. A. psilostachya prefers well-drained sandy or gravely soils. In Michigan, USA the species forms large clones by proliferation from underground parts in disturbed habitats such as along roadsides and railways and especially around populated areas (Wagner and Beals, 1958). In southern Saskatchewan and Manitoba, Canada, A. psilostachya is often found growing in sandy alkaline regions in open habitats (Bassett and Crompton, 1975). A. psilostachya preferentially colonizes non-saline soil over saline soil and clones with the strongest preference for non-saline soil are those least able to grow when restricted to saline conditions. In clonal plant species, non-random associations of genotypes with specific environments may thus reflect habitat selection by plants as well as selective mortality imposed by different habitat patches (Murray and Mishkin, 1985). Salzman and Parker (1985) in laboratory conditions found that paired stems of A. psilostachya clones from natural saline basins survived and grew in salt water, yet dry weight gain of these plants was only 34% of that of plants grown with tap water.


This plant is a major forb species in mixed and tallgrass prairies (Vermeire and Gillen, 2000). Tallgrass prairie includes as representative species; Andropogon gerardii, Schizachyrium scoparium, Panicum virgatum, Sorghastrum nutans, Sporobolus asper, Dichanthelium [Panicum] oligosanthes, Ambrosia psilostachya and Psoralea tenuiflora (Gillen and McNew, 1987). In Texas, A. psilostachya is found in association with Croton spp., Setaria spp., Paspalum spp. and Panicum spp. (Baker and Guthery, 1990). Major species on sandhill rangeland in Oklahoma included Andropogon hallii, Schizachyrium scoparium, Sporobolus cryptandrus, Panicum virgatum, Calamovilfa gigantea, Bouteloua gracilis, Ambrosia psilostachya, Eriogonum annuum and Artemisia filifolia (Baker and Powell, 1979).

The seeds of A. psilostachya are an important food item for bobwhite quail (Colinus virginianus) in prairie (Vermeire and Gillen, 2000). This plant is forb of particularly high quality for deer (Odocoileus hemionus) and white-tailed deer (Odocoileus virginianus) nutrition (Soltero-Gardea, 1991; Soltero-Gardea et al., 1994).

Air Temperature

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Parameter Lower limit Upper limit
Absolute minimum temperature (ºC) -42
Mean annual temperature (ºC) 4 12
Mean maximum temperature of hottest month (ºC) 15 31
Mean minimum temperature of coldest month (ºC) -15 -4


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ParameterLower limitUpper limitDescription
Mean annual rainfall335750mm; lower/upper limits

Natural enemies

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Natural enemyTypeLife stagesSpecificityReferencesBiological control inBiological control on
Tarachidia candefacta Herbivore Leaves
Zygogramma disrupta Herbivore Leaves
Zygogramma suturalis Herbivore Leaves

Notes on Natural Enemies

Top of page Goeden and Ricker (1976) reported numerous phytophagous insects, representing 7 orders, 36 families and 113 or more species on A. psilostachya in southern California, USA. Most insects found attacking this native species were euryphagous, ectophagous, sap- and foliage-feeding species and about half reproduced on this plant. Seventeen of the 95 associates identified to species were stenophagous, and their hosts were apparently confined to the tribe Heliantheae. Thirty of these were minor or major pests of cultivars. Under laboratory conditions, nymphs of Melanoplus confusus Scud., M. bivittatus (Say), M. keeleri luridus (Dodge) developed normally on A. psilostachya (Bajoi and Knutson, 1977). The larvae of Ophraella notulata (F.) (Coleoptera: Chrysomelidae) were found to feed gregariously at first on A. psilostachya (Goeden and Ricker, 1985), causing 'shot-hole' damage before dispersing and skeletonizing the leaves. Under conditions which eliminate overwintering, O. notulata completed a generation each month throughout the year for 27 generations, but in the field about 3 generations a year were more likely. The last generation, developing in October-November, was the most numerous.

Means of Movement and Dispersal

Top of page Natural Dispersal (Non-Biotic)

A. psilostachya spreads primarily by rootstocks and secondary by seeds. Seeds of A. psilostachya are spread by wind and water from mother plants. In spring they transfer by water in ditches, canals and rivers (Moskalenko, 2001).

Vector Transmission (Biotic)

Seeds of A. psilostachya are eaten by bobwhite quail (Colinus virginianus) and whole plants and eaten by deer (Odocoileus hemionus) and white-tailed deer (Odocoileus virginianus) (Soltero-Gardea, 1991; Soltero-Gardea et al., 1994; Vermeire and Gillen, 2000). It is assumed that these seeds retain viability though this is not proven.

Agricultural Practices

Tillage may be the cause of movement because A. psilostachya can grow from rhizomes (Miziniak and Praczyk, 2002).

Accidental Introduction

The fruits of A psilostachya were found by Russian quarantine observations on imported wheat grain from Canada (Moskalenko, 2001), and this is possibly the greatest threat for further long-distance introduction.

Intentional introduction

It is unlikely to have been intentionally introduced.

Plant Trade

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Plant parts liable to carry the pest in trade/transportPest stagesBorne internallyBorne externallyVisibility of pest or symptoms
Flowers/Inflorescences/Cones/Calyx seeds
Fruits (inc. pods) seeds
Growing medium accompanying plants roots
True seeds (inc. grain) seeds
Plant parts not known to carry the pest in trade/transport
Seedlings/Micropropagated plants
Stems (above ground)/Shoots/Trunks/Branches

Impact Summary

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Animal/plant collections None
Animal/plant products Negative
Biodiversity (generally) None
Crop production Negative
Environment (generally) Negative
Fisheries / aquaculture None
Forestry production None
Human health Negative
Livestock production Negative
Native fauna Positive
Native flora Negative
Rare/protected species None
Tourism Negative
Trade/international relations Negative
Transport/travel None


Top of page Ambrosia spp. (incl. A. psilostachya) are weeds harmful to various crops in North America (Piper, 1978), Poland (Karnkowski, 2001), Russia and in other countries (Moskalenko, 2001). They cause severe drying of plants, impoverishment of the soil and yield reduction (Karnkowski, 2001), even though A. psilostachya does not appear to reduce the growth of standing prairie grasses in its native range (Vermeire and Gillen, 2000). Potential sesquiterpenoid allelochemicals were found in A. psilostachya, which have been shown to be active as phytoalexins or allelopathic agents (Elakovich et al., 1987). Leaf and rhizome extracts of A. psilostachya inhibited germination and early seedling growth in a range of Poaceae including wheat, oats and rye, reducing germination by an average of 19.5% and shoot and root growth by an average of 56.8%. Combined effects of reduced germination and growth resulted in test plants giving only 34.8% of the production of control plants grown in distilled water (Dalrymple and Rogers, 1983).

Social Impact

Top of page A. psilostachya sheds large quantities of air-borne pollen that causes hay fever symptoms (Wodehouse, 1971; Culver et al., 1988; Karnkowski, 2001), with the allergen 'amb pV' (A1 variant) isolated from A. psilostachya pollen (Ghosh et al., 1994). However, the more localized occurrence of plants and their smaller size lessens the importance of A. psilostachya as a cause of hay fever. Global warming could aggravate allergic hazards and thereby jeopardize public health in years to come because warming resulted in a 105% increase in A. psilostachya aboveground biomass (Wan et al., 2002).

Risk and Impact Factors

Top of page Invasiveness
  • Invasive in its native range
  • Proved invasive outside its native range
  • Highly adaptable to different environments
  • Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
  • Highly mobile locally
  • Has high reproductive potential
  • Has propagules that can remain viable for more than one year
Impact outcomes
  • Negatively impacts agriculture
  • Negatively impacts human health
  • Negatively impacts tourism
  • Reduced amenity values
Impact mechanisms
  • Competition - monopolizing resources
Likelihood of entry/control
  • Highly likely to be transported internationally accidentally
  • Difficult/costly to control


Top of page There are no known uses for A. psilostachya. Autoclaved water extracts and methanol extracts of A. psilostachya depressed growth of bacteria (Mallik and Tesfai, 1987).

Similarities to Other Species/Conditions

Top of page A. psilostachya is very similar in appearance to Ambrosia artemisiifolia except that the former is a perennial with horizontal creeping roots whereas the latter is an annual with a tap root (Bassett and Crompton, 1975). Moreover, leaves of A. psilostachya are more greyish green and not as finely divided as A. artemisiifolia. The fruits of A. psilostachya are smaller and have only one blunt spine (Moskalenko, 2001).

Prevention and Control

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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.

Mechanical Control

Mechanical damage of rhizome buds slightly influenced the regrowth of ragweed (Miziniak and Praczyk, 2002).

Chemical Control

For chemical control of A. psilostachya, aerially applied 2,4-D was as effective and more consistent than fenoprop and dichlorprop, with late April and early May the optimum time for spraying (Elwell and McMurphy, 1973). Picloram, dicamba and 2,4-D provided effective control of A. psilostachya in pastures when applied for 2 successive years (Hoffman, 1972; McCarty and Scifres, 1972). Dahl et al. (1989) found that triclopyr and dicamba + 2,4-D were ineffective, but picloram + 2,4-D and dicamba gave adequate control of A. psilostachya. Picloram is recommended for control of A. psilostachya in Mauritius (McIntyre, 1985). Atrazine applied in April also reduced the density of A. psilostachya (Baker, 1979; Rice and Stritzke, 1985; 1986; 1989; Gillen et al., 1987).

Biological Control

Zygogramma suturalis (F.) (Coleoptera, Chrysomelidae) was introduced from North America for the biological control of Ambrosia spp. and released in several countries, including Russia in 1978 (Reznik et al., 1994), Yugoslavia in 1984 (Igrc, 1987), Croatia in 1985 (Igrc et al., 1995) and China in 1997 and 1998 (Wan and Wang, 1989; 1990). The larvae and adults of the Z. suturalis were able to feed and develop on A. artemisiifolia and A. psilostachya in the natural environment (Kovalev et al., 1983; Kovalev and Vecherin, 1986; Reznik and Kovalev, 1989). However, 10 years after it was introduced into Russia, Z. suturalis was only moderately successful as a biological control agent due to low population establishment (Reznik et al., 1994) and poor movement (Reznik et al., 1990). The second natural enemy of Ambrosia spp., Zigogramma disrupta (Rogers) was introduced into the former USSR from Texas, USA in 1981 for the biological control of A. artemisiifolia and A. psilostachya (Kovalev et al., 1983), with the adults and larvae feeding on the uppermost foliage of the plant (Piper, 1978). The western biotype of Tarachidia candefacta (Hb.) (Lepidoptera, Noctuidae) was introduced from California, USA into the former USSR in 1967 for the biological control of Ambrosia spp. (Nayanov, 1973; Gilstrap and Goeden, 1974; Kovalev, 1989) and was found to have acclimatized in Krasnodar region, Southern Russia (Shurov, 1998).


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Allard HA, 1943. The North American ragweeds and their occurrence in other parts of the world. Science, 98:292-294.

Anon., 1970. Handbook on Quarantine and other Noxious Pests. Moscow, Russia: Kolos.

Auld B; Medd R, 1992. Weeds. An illustrated botanical guide to the weeds of Australia. Melbourne, Australia: Inkata Press.

Bajoi AH; Knutson H, 1977. Effects when restricting an acridid species to a specific plant species. Acrida, 6(3):219-229

Baker DL; Guthery FS, 1990. Effects of continuous grazing on habitat and density of ground-foraging birds in south Texas. Journal of Range Management, 43(1):2-5.

Baker RL, 1979. Response of Oklahoma Rangeland to atrazine, 2,4-D, and fertilizer. Dissertation Abstracts International, B, 39(8):3625-3626

Baker RL; Powell J, 1979. Western Oklahoma sandhill prairie yield and crude protein response to atrazine, nitrogen, and 2,4-D during drought. Arid lands plant resources: proceedings of the international arid lands conference on plant resources, Texas Tech University (J. R. Goodin and D. K. Northington, editors). Texas Tech University, International Center for Arid and Semi-Arid Land Studies (ICASALS). Lubbock, Texas USA, 564-573

Bassett IJ; Crompton CW, 1975. The biology of Canadian weeds. 11. Ambrosia artemisiifolia L. and A. psilostachya DC. Canadian Journal of Plant Science, 55(2):463-476

Bassett IJ; Terasmae J, 1962. Ragweeds, Ambrosia species, in Canada and their history in postglacial time. Canadian Journal of Botany, 40:141-150.

Beres I, 2003. Distribution, importance and biology of common ragweed (Ambrosia artemisiifolia L.). Novenyvedelem, 39(7):293-302.

Berg WA; Bradford JA; Sims PL, 1997. Long-term soil nitrogen and vegetation change on sandhill rangeland. Journal of Range Management, 50(5):482-486.

Britton NL; Brown A, 1970. An illustrated flora of the northern United States and Canada, Vol. III, edition. New York, USA: Dover Publications, Inc.

Buyankin VI, 1975. New weeds of the Ural'sk Province. Botanicheskii Zhurnal, 60(8):1190-1191

Crothers M, 1993. Ragweed (Ambrosia spp.). Ambrosia artemisiifolia L. (annual ragweed). Ambrosia psilostachya D.C. (perennial or western ragweed). Agnote (Darwin), No. 552:2 pp.

Culver CA; Malina JJ; Talbert RL, 1988. Probable anaphylactoid reaction to a pyrethrin pediculocide shampoo. Clinical-Pharmacology, 7 (11): 846-849.

Dahl BE; Mosley JC; Cotter PF; Dickerson RL Jr, 1989. Winter forb control for increased grass yield on sandy rangeland. Journal of Range Management, 42(5):400-403

Dalrymple RL; Rogers JL, 1983. Allelopathic effects of western ragweed on seed germination and seedling growth of selected plants. Journal of Chemical Ecology, 9(8):1073-1078

Eardley CM, 1944. Control of perennial ragweed (Ambrosia psilostachya). Journal of Department Agricultural South Australia, 47:430-434.

Elakovich SD; Fuller G; Nes WD, 1987. Sesquiterpenes as phytoalexins and allelopathic agents. Ecology and Metabolism of Plant Lipids. ACS Symposium Series No. 325, 93-108.

Elwell HM; McMurphy WE, 1973. Weed control with phenoxy herbicides on native grasslands. Bulletin, Agricultural Experiment Station, Oklahoma State University, No. B-706:24 pp.

EPPO, 2014. PQR database. Paris, France: European and Mediterranean Plant Protection Organization.

Ghosh B; Rafnar T; Perry MP; Bassolino-Klimas D; Metzler WJ; Klapper DG; Marsh DG, 1994. Immunologic and molecular characterization of Amb p V allergens from Ambrosia psilostachya (Western Ragweed) pollen. Journal of Immunology (Baltimore), 152(6):2882-2889; 38 ref.

Gillen RL; McNew RW, 1987. Seasonal growth rates of tallgrass prairie after clipping. Journal of Range Management, 40(4):342-345.

Gillen RL; Rollins D; Stritzke JF, 1987. Atrazine, spring burning, and nitrogen for improvement of tallgrass prairie. Journal of Range Management, 40(5):444-447

Gilstrap FE; Goeden RD, 1974. Biology of Tarachidia candefacta, a Nearctic Noctuid introduced into the U.S.S.R. for ragweed control. Annals of the Entomological Society of America, 67(2):265-270

Goeden RD; Ricker DW, 1976. The phytophagous insect fauna of the ragweed, Ambrosia psilostachya, in southern California. Environmental Entomology, 5(6):1169-1177

Goeden RD; Ricker DW, 1985. The life history of Ophraella notulata (F.) on western ragweed, Ambrosia psilostachya De Candolle, in southern California (Coleoptera: Chrysomelidae). Pan-Pacific Entomologist, 61(1):32-37

Hoffman GO, 1972. Control of perennial weeds on rangelands with fall application of herbicides. Proceedings 25th Annual Meeting Southern Weed Science Society, 318-319.

Igrc J, 1987. The importance of the species Ambrosia artemisiifolia in the world and in Yugoslavia. Fragmenta Herbologica Jugoslavica, 16(1-2):47-55

Igrc J; DeLoach CG; Zlof V, 1995. Release and establishment of Zygogramma suturalis F. (Coleoptera: Chrysomelidae) in Croatia for control of common ragweed (Ambrosia artemisiifolia L.). Biological Control, 5:203-208.

Karnkowski W, 2001. Can the weeds be recognized as quarantine pests? - Polish experiences with Ambrosia spp. Zbornik predavanj in referatov 5. Slovensko Posvetovanje o Varstvu Rastlin, C^hacek~atez^hacek~ ob Savi, Slovenija, 6. marec-8. marec 2001, 396-402; 21 ref.

Kovalev OV; Reznik SYa; Cherkashin VN, 1983. Characteristics of methods of using leaf-beetles of the genus Zygogramma Chevr. (Coleoptera, Chrysomelidae) in the biological control of ragweeds (Ambrosia artemisiifolia L., A. psilostachya D.C.). Entomologicheskoe Obozrenie, 62(2):402-408

Kovalev OV; Vecherin VV, 1986. Description of a new wave process in populations, with reference to the introduction and spread of the ambrosia leaf beetle Zygogramma suturalis F. (Coleoptera, Chrysomelidae). Entomologicheskoe Obozrenie, 65(1):21-38

Lawalrée A, 1947. Les Ambrosia adventices en Europe occidentale. Bull. Jard. Bot. Etat Bruxelles, 18:305-315.

Lorenzi HJ; Jeffery LS, 1987. Weeds of the United States and their Control. New York, USA:Van Norstrand Reinhold Co.

Mallik MAB; Tesfai K, 1987. Stimulation of Bradyrhizobium japonicum by allelochemicals from green plants. Plant and Soil, 103(2):227-231; [2 fig., 2 tab.]; 19 ref.

McCarty MK; Scifres CJ, 1972. Herbicidal control of western ragweed in Nebraska pastures. Journal of Range Management, 25(4):290-292.

McIntyre LFG, 1985. Weed control in various food crops in Mauritius with particular reference to mixed cropping. Revue Agricole et SucriFre de l'Ile Maurice, 64(2):111-116

Miller HE; Mabry TJ; Turner BL and Payne WW, 1968. Infraspecific variation of sequiterpene lactones in Ambrosia psilostachya (Compositae). American Journal of Botany, 55:316-324.

Miziniak W; Praczyk T, 2002. Regrowth of Ambrosia psilostachya D.C. from rhizomes on different type of soils. Progress in Plant Protection, 42(2):547-550; 3 ref.

Moskalenko GP, 2001. Quarantine Weeds for Russia. Moscow, Russia: Plant Quarantine Inspectorate.

Moskalenko GP, 2002. Perennial ragweed. Zashchita i Karantin Rastenii^breve~, No.3:36-37.

Mulligan GA, 1957. Chromosome numbers of Canadian weeds. Canadian Journal of Botany, 35:779-789.

Murray EA; Mishkin M, 1985. Habitat selection in a clonal plant. Science (USA), 228(4699):603-604.

Nayanov NI, 1973. Acclimatization of Tarachidia candefacta Hubn. (Lepidoptera, Noctuidae) in the south of the European part of the USSR. Entomologicheskoe Obozrenie, 52(4):759-767

Payne WW, 1970. Preliminary reports on the flora of Wisconsin. LXII. Compositae-composite family. 6. The genus Ambrosia-the ragweeds. Transact. Wisconsin Acad. Sci, 58:353-371.

Payne WW; Raven PH and Kyhos DW, 1964. Chromosome numbers in Compositae. American Journal of Botany, 51:419-424.

Peoples AD; Lochmiller RL, Leslie DM Jr. , Engle DM, 1994. Production and nutritional quality of western ragweed seed in response to fertilization. Journal of Range Management, 47(6):467-469.

Piper GL, 1978. Life history of Zygogramma disrupta in southeast Texas (Coleoptera: Chrysomelidae). Pan-Pacific Entomologist, 54(3):226-230

Prasad TVR; Rao RR; Sanjay MT; Sharma RA, 2013. .

Reznik SY; Belokobyl' skii SA; Lobanov AL, 1994. Weed and herbivourous insect popoulation densities at the broad spatial scale: Ambrosia artemisiifolia L. and Zygogramma suturalis F. (Col., Chrysomelidae). Journal of Applied Entomology, 118:1-9.

Reznik SYa; Belokobyl'skii SA; Lobanov AL, 1990. Effect of agroecosystem stability on the population density of the ambrosia leaf beetle Zygogramma suturalis (Coleoptera, Chrysomelidae). Zoologicheskii Zhurnal, 69(10):54-59

Reznik SYa; Kovalev OV, 1989. Foraging and food selection behaviour of the imago of the ambrosia leaf beetle. Trudy Zoologicheskii, Institut Akademii Nauk SSSR, 189:56-61

Rice CK; Stritzke JF, 1985. The comparison of 2,4-D and atrazine for the control of pasture weeds. Proceedings, Southern Weed Science Society, 38th annual meeting Champaign, Illinois, USA, 12

Rice CK; Stritzke JF, 1986. Weed control and grass release associated with one- and two-year use of atrazine and 2,4-D. Proceedings, Southern Weed Science Society, 39th annual meeting, 152

Rice CK; Stritzke JF, 1989. Effects of 2,4-D and atrazine on degraded Oklahoma grasslands. Journal of Range Management, 42(3):217-222

Royal Botanic Gardens Sydney, 2003. Australia's Virtual Herbarium. Sydney, Australia: Royal Botanic Gardens.

Rydberg PA, 1965. Flora of the prairies and plains of Central North America. New York and London: Hafner publisching Company.

Salzman AG; Parker MA, 1985. Neighbors ameliorate local salinity stress for a rhizomatous plant in a heterogeneous environment. Oecologia, 65(2):273-277.

Shurov VI, 1998. Acclimation of the American ragweed cutworm. Zashchita I Karantin Rastenii, 12:31-32.

Soltero-Gardea S, 1991. Phytomass dynamics and deer and cattle nutrition under different grazing practices in the Texas Coastal Bend. Dissertation Abstracts International. B, Sciences and Engineering, 52(5): 2379B. Abstract of Thesis. USA: Texas Tech University.

Soltero-Gardea S; Ortega IM; Bryant FC, 1994. Nutrient content of important deer forage plants in the Texas coastal bend. Texas Journal of Science, 46(2):133-142.

Spencer ER, 1957. Just Weeds. New York, USA: Charles Scribner's Sons.

Tutin TG; Heywood VH; Burges NA; Moore DM; Valentine DH; Walters SM, Webb DA (et al. editors), 1976. Flora Europaea. Volume 4. Plantaginaceae to Compositae (and Rubiaceae). Cambridge, UK: University Press, xxix + 505 + 5pp + 5 maps.

USDA-ARS, 2003. Germplasm Resources Information Network (GRIN). Online Database. Beltsville, Maryland, USA: National Germplasm Resources Laboratory.

USDA-NRCS, 2002. The PLANTS Database, Version 3.5. National Plant Data Center, Baton Rouge, USA.

Vermeire LT; Gillen RL, 2000. Western ragweed effects on herbaceous standing crop in Great Plains grasslands. Journal of Range Management, 53(3):335-341.

Wagner WH; Beals TF, 1958. Perennial ragweed (Ambrosia) in Michigan, with the description of a new, intermediate taxon. Rhodora, 60:177-204.

Wan FH; Wang R, 1989. Biology of Zygogramma suturalis (F.) (Col.: Chrysomelidae), an introduced biological control agent of common ragweed, Ambrosia artemisiifolia. Chinese Journal of Biological Control, 5(2):71-75

Wan FH; Wang R, 1990. A cage study on the control effects of Ambrosia artemisiifolia by the introduced biological control agent, Zygogramma suturalis (Col.: Chrysomelidae). Chinese Journal of Biological Control, 6(1):8-12

Wan SQ; Yuan T; Bowdish S; Wallace L; Russell SD; Luo YQ, 2002. Response of an allergenic species, Ambrosia psilostachya (Asteraceae), to experimental warming and clipping: implications for public health. American Journal of Botany, 89(11):1843-1846; 37 ref.

Wodenhouse RP, 1971. Hayfever Plants. Edition 2. New York, USA: Hafner Publ. Co.

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