Ambrosia artemisiifolia
(common ragweed)

A. artemisiifolia is an annual herb native to Central and Northern America. It has been accidentally introduced into a large number of countries as a contaminant of seed and grains. A. artemisiifolia typically colonises disturbed land where it produces a large number of seeds which can remain viable in the soil for 40 years or more. The pollen produced by species of Ambrosia is highly allergenic and can induce allergic rhinitis, fever, or dermatitis. As a result, high medical costs have been reported in areas with large infestations in both its native and introduced range. A. artemisiifolia can also invade agricultural land where it acts as a weed in a number of crops (in particular in sunflower, maize, soybean and cereals) and can cause significant decreases in yields.

A. artemisiifolia is native to North and Central America (Lorenzi and Jeffery, 1987; Kovalev, 1989). It is now widely distributed across the world; Africa (CJB, 2016), Asia (Flora of China Editorial Committee, 2011), Australia (Council of Heads of Australasian Herbaria, 2016) and Europe (Euro+Med, 2016).

A. artemisiifolia has become a dominant alien plant in countries such as Italy (Siniscalo and Barni, 1994), Lithuania (Gudzinskas, 1993) and Hungary. A. artemisiifolia is not as prominent in subtropical and tropical regions (Allard, 1943; King, 1966). The hot, dry summers in southern Europe and Mediterranean areas are not favourable for its growth (Allard, 1943; King, 1966). In addition to this A. artemisiifolia is relatively rare in northern Europe (Norway, Sweden, Scotland and Ireland) (Gerber et al., 2011).

It is possible that A. artemisiifolia will spread further as it is accidentally introduced as a contaminant of seed and grain into other countries. Temperature is the main factor limiting the spread of A. artemisiifolia; under cooler conditions plants fail to produce flowers or seeds fail to ripen (Bullock et al., 2010). It is possible that as a result of climate change, A. artemisiifolia may increase its distribution.

A. artemisiifolia is typically found on disturbed sites such as, railways, wasteland, uncultivated and cultivated land (field crops, orchards, vineyards, nurseries) and constructions sites. It is naturally found along river banks but may also be found in grasslands and dry meadows.

Experiments carried out by Vidotto et al. (2013) showed that A. artemisiifolia inhibits the germination and growth of tomato (Solanum lycopersicum) by more than 50%. The same authors showed also a reduction in growth for lettuce (Brassica spp.). In corn, season-long interference from dense populations of A. artemisiifolia in Illinois was found to reduce yields by 74% in two years. A. artemisiifolia also has an impact on the growth of peanuts (Arachis hypogaea) and was ranked as one of the worst weeds to control during cultivation (Wilcut and Swann, 1990; Clewis et al., 2002).

Genetics

A. artemisiifolia is a diploid taxon with 2n = 36 (CCDB, 2016). Hybrids were described with A. psilostachya (A. × integradiensis W.H.Wagner) and A. trifida L. (A. × helenae Rouleau) (Strother, 2006).

Reproductive Biology

A. artemisiifolia is a fast growing herb which can completes its growth cycle in 115 to 183 days (Bassett and Crompton, 1975; Li et al., 1989; Beres, 1994), with each plant producing a high number of viable seeds which are small in size and low in weight (Yurukova-Grancharova et al., 2015). Pollination is performed by wind, the pollen being small (20-30 µm), tricolporate, sphaerical, with short and sparse spines andcavae (Payne et al., 1970; Bassett et al., 1978).

Physiology and Phenology

A. artemisiifolia uses the C3 pathway of photosynthesis. It is one of the earliest emerging summer annual weed species and may germinate once soil temperatures reach 11-13°C (Forcella et al., 1997). It is a pioneer annual in temperate regions, and rapidly succeeds in the first year of old fields from buried seed (Ohtsuka, 1998). In the autumn, ploughing generally favours establishment of this weed (Altieri and Liebman, 1988).

Photoperiod and temperature are the main factors affecting growth and development of A. artemisiifolia (King, 1966; Deen et al., 1998). Flowering starts approximately 119 days after germination (Li et al., 1989). Long days favour the development of male flowers, whereas female flowers are favoured by shortened days (King, 1966). Increasing of atmospheric CO₂ in urban areas resulted in increased pollen production by A. artemisiifolia according to Ziska et al. (2003). Feher et al. (1998) reported that high daily temperatures and great variations of diurnal temperatures promoted pollination, whereas rain, clouds and humid weather reduced pollination. Typically, peak pollen production often occurs from mid-August to mid-September (Albasser, 1992).

Anthers open with a rise in temperature and low relative humidity (King, 1966). The adaptability of the plant to cooler climates in Hungary has been demonstrated by shortening the time from germination to flowering and seed ripening (Beres, 1994). A study carried out in the USA, using plants originating from Indiana, Michigan, Ohio and Wisconsin, suggested the existence of common ragweed ecotypes based on origin of the seeds (Leif et al., 2000).

Flowering occurs from July to October in both the origin and non-native ranges. Seeds have a low rate of germination at maturity (Sahoo, 1998) and usually require winter stratification before germination; however, seeds may undergo secondary dormancy (Altieri and Liebman, 1988). The burial of seeds increases the non-dormant seed population of A. artemisiifolia by 0.5 to 7.1% (Sahoo, 1998).

One plant may produce 3,000-4,000 seeds (Beres, 1994; Beres et al., 2002). However, up to 32,000 seeds have been counted in a single plant (Bassett and Crompton, 1975). Seed production by A. artemisiifolia may be reduced over 80% depending on its emergence relative to the crop growth stage (Chikoye et al., 1995).

A. artemisiifolia seeds may survive up to 40 years (King, 1966). Germination of seeds is decreased when stored in cattle slurry and was significantly influenced by the time of storage in maize silage. Seeds stopped germinating after 3-5 months in cattle slurry (following storage in maize silage) or after storage in maize silage for 13 months (Lesnik, 2001).

A. artemisiifolia contains phenolic compounds and terpenes (Beres et al., 2002). The allelopathic influences of A. artemisiifolia were tested in bioassays on soyabean, black gram, rice and maize. Aqueous extracts of dried fresh leaves of the weed significantly suppressed the germination, plumule and radicle length of all crops tested. Toxicity increased with the increase in concentration of extracts. The effect of the extracts was greater on the germination of black gram and rice compared to soyabean and maize. A chloroform extract from A. artemisiifolia inhibited the growth and decreased the chlorophyll a concentrations of two green algae (Chlorella vulgaris and Chlamydomonas sp.) (Bruckner et al., 2001).

Environmental Requirements

A. artemisiifolia is susceptible to frost and is commonly found between 30-50° at both north and south latitudes in diverse settings (King, 1966). It rarely grows above altitudes of 1000 m (Allard, 1943). It can grow in clay or sandy soils, but grows well on wet, heavy soils at pH 6.0-7.0 (Bassett and Crompton, 1975).

Several natural enemies have been recorded from A. artemisiifolia as this species has been the focus of numerous biological control programmes. Maceljski and Igrc (1990) reported 28 insects including five Orthoptera, three Heteroptera, four Homoptera, six Coleoptera and nine Lepidoptera that fed on A. artemisiifolia. However, several of these insects are common crop pests. According to Julien et al. (2012) more than 70 arthropods have been recorded from A. artemisiifolia in its native range and a total of 20 pathogens identified from Eurasia including Puccinia xanthii (Gerber et al., 2011).

A. artemisiifolia may also serve as an alternative host for crop diseases such as Meloidogyne arenaria race 2 (Tedford and Fortnum, 1988), M. incognita race 3 (Tedford and Fortnum, 1988), Erysiphe cichoracearum (Bassett and Crompton, 1975), Albugo tragopogonis (Bassett and Crompton, 1975), Plasmopara halstedii (Bassett and Crompton, 1975), Entyloma compositarum (Bassett and Crompton, 1975), Entyloma polysporum (Bassett and Crompton, 1975), Puccinia xanthii (Bassett and Crompton, 1975), Aster yellow virus (Bassett and Crompton, 1975), Cucumber mosaic virus (Kazinczi et al., 2001), Cuscuta gronovii (Bassett and Crompton, 1975), Protomyces gravidus (Cartwright and Templeton, 1988), Septoria sp. (Bohár and Schwarczinger, 1999), Phoma sp. (Briere et al., 1995) and Sclerotinia sclerotiorum of sunflower (Bohár and Kiss, 1999). 

Environmental

• Soil improvement

Materials

• Chemicals

Medicinal, pharmaceutical

• Source of medicine/pharmaceutical
• Traditional/folklore

Auda et al. (2002) and Danner et al. (2012) showed that it may soon be possible to detect dense populations of A. artemisiifolia using spatial remote sensing methods.

A. artemisiifolia is similar in appearance to a number of species in the genus Ambrosia.

For example, it is similar to A. acanthicarpa from which differs by the narrower capitula (2-3 vs. 3-7 mm), the shape and lenght of fruits (globose to pyriform, 2-3 mm long vs. more or less fusiform, 3-5 mm long), number and lenght of spines in the fruits (3-5 spines each 0.1-0.5 mm long vs. 8-18 spines each 8-18 mm long) (Strother, 2006).

Another similar species is A. annua which is mainly different by its inflorescence with capitula arranged in panicles.

A. trifida grows taller, has larger seed and has palmate leaves divided into three lobes compared with A. artemisiifolia.

A. bidentata has hairy, notched leaves that clasp the stem. Seed are angled with prominent spines.

A. psilostachya is a perennial with leaves not as finely divided as A. artemisiifolia.

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.

Control

Cultural Control

Planting red clover (Trifolium pretense) as a cover crop in established winter wheat reduced the biomass of A. artemisiifolia (Mutch et al., 2003).

Mechanical Control

A. artemisiifolia may be controlled by hand weeding, mowing (at 2 cm, from the soil) and by crushing with a roadroller (Vincent et al., 1992). Hand weeding is the most effective in reducing pollen and seed production although it is also the most expensive (Vincent et al., 1992). Mechanical cutting can reduce A. artemisiifolia seed production by up to 74% depending on the number and timing of cuttings (Guan et al., 1991).

Biological Control

A. artemisiifolia has been the subject of a biocontrol programme which has resulted in the release of a number of agents.

Zygogramma suturalis (ambrosia striped leaf beetle) has a preferential appetite for A. artemisiifolia (Igrc and Ilovai, 1996). The beetle may consume 50-70% of the leaf surface area (Kuznetsov et al., 1987). Z. suturalis was introduced from North America into several countries including Russia in 1978 (Reznik et al., 1994), former Yugoslavia in 1984 (Igrc, 1987) and Croatia in 1985 (Igrc et al., 1995). Z. suturalis was introduced from Canada and Russia to China in 1997 (Wan and Wang, 1989) and 1988 (Wan and Wang, 1990). However, 10 years after it was introduced into Russia it was only moderately successful due to low population establishment (Reznik et al., 1994) and poor movement (Reznik et al., 1990).

A. artemisiifolia is a known host for Ophraella communa (ragweed leaf beetle) (Knowles et al., 1999). O. communa was introduced into Japan in 1996 (Moriya, 1999; Yamazaki et al., 2000; Moriya and Shiyake, 2001; Moriya et al., 2002) and Taiwan (Wang and Chiang, 1998). Tarachidia candefacta was introduced into Russia from Canada in 1967 and became established (Shurov, 1998).

Potential biological control agents such as Epiblema strenuana (Wan, 1991), Pseudomonas syringae pv. tagetis (Johnson et al., 1996), Protomyces gravidus (Cartwright and Templeton, 1988) Phyllachora ambrosiae (Vajna et al., 2000) and Septoria epambrosiae (Bohár and Schwarczinger, 1999; Becker, 2001; Farr and Castlebury, 2001) have been pursued and the possibility of biological control of A. artemisiifolia is still being considered.

In the autumn of 2001, an epidemic of downy mildew (Plasmopara halstedii) occurred on A. artemisiifolia over large areas of central Hungary (Vajna, 2002).

The herbicidal effect of essential oils (1%, v/v) from red thyme (Thymus vulgaris L.), summer savory (Satureja hortensis L.), cinnamon (Cinnamomum zeylanicum Blume) and clove [Syzygium aromaticum (L.) Merr. & L.M.Perry] on shoots of A. artemisiifolia was determined in laboratory and greenhouse experiments (Tworkoski, 2002). The oils may be useful as natural product herbicides for organic farming systems.

Sesquiterpenoid lactones extracted from A. taurica were highly toxic against the seeds of A. artemisiifolia (C50 10.4-56.8 mg/litre) (Konovalov et al., 2002).

Chemical Control

A number of post- and pre-emergence chemicals have been used to control A. artemisiifolia with varied success.

Pre-emergence application of mesotrione controlled A. artemisiifolia by at least 80%, whereas post-emergence provided control from 56-97% (Armel et al., 2003).

Diphenyl ether herbicides (lactofen, fomesafen and acifluorfen) (Holowid and Smith, 1986; Monks et al., 1993; Zhan et al., 1993; Lee et al., 1995; Nelson and Renner, 1998), cloransulam-methyl (Nelson and Renner, 1998, Askew et al., 1999) and chlorimuron (Moseley and Hagood, 1991, Monks et al., 1993, Prostko and Meade, 1993) have been used for post-emergence control of A. artemisiifolia in soybean. Pre-emergence use of flumioxazin and chlorimuron plus metribuzin controlled A. artemisiifolia in no-till soybean (Niekamp et al., 1999; Niekamp and Johnson, 2001) whereas glufosinate alone controlled A. artemisiifolia in glufosinate-resistant soybean by more than 85% (Beyers et al., 2002).

In maize, Isoxaflutole (Luscombe and Pallett, 1996; Sprague et al., 1999), atrazine (Culpepper and York, 1999), diflufenzopyr plus dicamba (Sikkema et al., 1999), atrazine plus bromoxynil (Wiese et al., 1986) and atrazine plus bentazone (Hamill and Zhang, 1997) have been used to control A. artemisiifolia. However, herbicide resistance of A. artemisiifolia to atrazine has been reported (Igrc, 1987, Maceljski and Igrc, 1990). Dicamba and rimsulfuron plus thifensulfuron-methyl tank-mixed with primisulfuron-methyl were also found to control A. artemisiifolia in maize by at least 88% (Isaacs et al., 2002).

For spring barley, Metsulfuron-methyl, 2,4-D plus dicamba, and triasulfuron plus dicamba plus 2,4-D controlled A. artemisiifolia (Zhidkov et al., 2002).

For control of A. artemisiifolia in peanut, bentazone plus paraquat followed by imazapic (Richburg et al., 1996), acifluorfen plus bentazone (Wilcut, 1991; York et al., 1995), acifluorfen plus 2,4-DB (Wilcut, 1991), preplant incorporated tank-mixtures (Jordan et al., 1994), ethalfluralin plus vernolate preplant incorporated and paraquat applied one week after emergence (Wilcut and Swann, 1990) have been used successfully. Pre-emergence treatments of diclosulam controlled common ragweed by 100% (Price and Wilcut, 2002).

In glyphosate-tolerant cotton, A. artemisiifolia was controlled with clomazone pre-emergence and glyphosate (Scott et al., 2002). Flumioxazin tank-mixed with the isopropylamine salt of glyphosate, paraquat or the trimethylsulfonium salt of glyphosate controlled common ragweed by 96%, 29 to 43 days after treatment in strip-tillage cotton (Price et al., 2002). Bromoxynil plus pyrithiobac post-emergence or with MSMA controlled (90%) common ragweed in bromoxynil-resistant cotton early season.

In other crops, A. artemisiifolia has been controlled with fluroxypyr in small grains (Riggle et al., 1999), oxyfluorfen in broccoli (Eaton et al., 1990), sulfometuron in Pinus taeda seedlings (Miller, 1990), terbacil applied pre-emergence in watermelon (Beste, 1989) and clopyralid in rutabagas (Brolley, 1990). In tomato (Ackley et al., 1997) or potato (Ackley et al., 1996), control of A. artemisiifolia was attained with rimsulfuron plus metribuzin, or metribuzin plus metolachlor applied pre-emergence in potato (Hoyt and Monks, 1996; Bailey et al., 2001).

An acetolactate synthase (ALS)-resistant A. artemisiifolia biotype has been found in Indiana (Patzoldt et al., 2001) and Ohio, USA (Taylor et al., 2002).

IPM

Crop rotations using herbicides that control A. artemisiifolia are crucial for managing A. artemisiifolia in sunflower (Helianthus annuus) fields. Mechanical weed control of A. artemisiifolia and other weeds has been shown to increase seed yield of sunflower (Fleck et al., 1989).

More detailed phytosociological studies of non-native areas in which A. artemisiifolia is naturalized/invasive could be conducted to provide a better insight on the impact of this species.

06/11/2016 Updated by:

Duilio Iamonico, University of Rome Sapienza, Rome, Italy