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EUROPEAN AND MEDITERRANEAN PLANT PROTECTION ORGANIZATION
ЕВРОПЕЙСКАЯ И СРЕДИЗЕМНОМОРСКАЯ ОРГАНИЗАЦИЯ ПО КАРАНТИНУ И ЗАЩИТЕ РАСТЕНИЙ
ORGANISATION EUROPEENNE ET MEDITERRANEENNE POUR LA PROTECTION DES PLANTES
02/9303
P PM Point 7.8
Ambrosia spp.
IDENTITY

Ambrosia artemisiifolia
Name:
Ambrosia artemisiifolia L.
Synonyms:
Ambrosia elatior L., Ambrosia elata Salisb., Ambrosia paniculata Michx.,
Ambrosia maritima L.
Taxonomic position: Asteraceae
Common name:
common ragweed (English); амброзия полыннолистная (Russian).
Bayer code: AMBEL

Ambrosia psilostachya
Name:
Ambrosia psilostachya D.C.
Synonyms:
Ambrosia coronopifolia Torr. & Gray, Ambrosia californica Rydb., Ambrosia
cumanensis Kunth., Ambrosia peruviana D.C., Ambrosia rugelii Rydb.
Taxonomic position: Asteraceae
Common name:
perennial ragweed, western ragweed (English); амброзия многолетняя,
амброзия голометельчатая (Russian).
Bayer code: AMBPS

Ambrosia trifida
Name:
Ambrosia trifida L.
Synonyms:
Ambrosia integrifolia Muhl.
Taxonomic position: Asteraceae
Common name: giant ragweed (English); амброзия трёхраздельная (Russian).
Bayer code: AMBTR
GEOGRAPHICAL DISTRIBUTION

Ambrosia artemisiifolia
Europe: Austria, Belgium, Czech Republic, France, Germany, Hungary, Italy, Moldova, Poland,
Portugal, Romania, Russia (Krasnodar territory, Primorskii territory), Slovakia, Sweden,
Switzerland, UK, Ukraine, Yugoslavia.
Asia: Azerbaijan, Japan, Kazakhstan, Korea.
North America: Canada, Mexico, USA (incl. Hawaii).
Africa: Mauritius
Central & South America: Argentine, Bolivia, Brazil, Chile, Colombia, Cuba, Guadeloupe,
Guatemala, Jamaica, Martinique Paraguay, Peru, Uruguay.
Oceania: Australia, New Zealand.
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
Ambrosia psilostachya
Europe: Belgium, Denmark, France, Germany, Hungary, Italy, Netherlands, Poland, Russia
(limited areas in the South of European Russia), Spain, Sweden, Switzerland.
Asia: Kazakhstan.
Africa: Mauritius
North America: Canada, Mexico, USA.
Oceania: Australia.

Ambrosia trifida
Europe: Belgium, Czechia, France, Germany, Italy, Netherlands, Norway, Russia (South of
European Russia), Sweden, Switzerland, Yugoslavia.
Asia: Georgia, Japan.
North America: Canada, Mexico, USA.
Remark: Ambrosia spp. are native to North America and have spread from there to many other
areas in the world (except perhaps Africa).
ON WHICH CROPS
Ambrosia spp. can infest practically all field crops (cereals, maize, soybean, sunflower, root
crops, etc.), meadows, pastures, orchards and vineyards, and also rangeland. However, they are
commonest along waterways, roads, railways and in wasteland.
BIOLOGY
A. artemisiifolia is an annual weed. It reproduces by seeds. One plant may develop 30.000 to
40.000 seeds. Seeds can keep their vitality 5 to 14 years. On heavily infested plots, the
population rate can reach till 500 plants/m2. Seeds germinate in warm and well-aerated soil. The
plants secrete phytotoxic substances.
A. psilostachya is a perennial weed. It reproduces mainly by rhizomes. Few seeds are formed,
but they are important in spreading the weed over long distances.
A. trifida is an annual weed. It reproduces by seeds. Its biology is similar to that of A.
artemisiifolia, but it is more frost-resistant, develops faster, and its mature seeds appear earlier.
DETECTION AND IDENTIFICATION
A. artemisiifolia grows 20-180 cm tall, sometimes reaching 250 cm. The stem is upright, angular,
much branched. The whole plant is hairy The leaves are pinnatifid, 5-10 cm long. The root is
vertical, and can reach a depth of 4 m. Male and female flowers are borne in separate fewflowered heads, the male heads in long inflorescences at the tips of the shoots, and the female
ones in the axils of the leaves and at the base of the male inflorescence. The fruit is ovate 2.2-3.2
mm long, 1.5-2.0 mm wide, narrowed at the base, with 5 to 7 small lateral thorns and one bigger
thorn at the tip.
A. psilostachya has an upright stem reaching 100 cm or more. The lower leaves are opposite, and
the upper alternate. The leaves are pinnatifid, petiolate, 5-12 cm long. The stem, leaves and
branches are covered with dense hairs, giving the plant a grey-green colour. Inflorescences are
similar to those of A. artemisiifolia, but male inflorescence is denser, 7 to 15 cm long and may
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contain 50 to 100 heads of flowers. The fruits are similar to those of A. artemisiifolia, 2.5-3.0
mm long, 2.0-2.5 mm wide, but with lateral thorns not well developed or absent.
A. trifida has an upright stem reaching 100 cm and more (exceptionally 300 cm). The leaves are
opposite, 3-palmately lobed (lower leaves may be 5-palmately lobed, higher leaves may be nonlobed), petiolate. The inflorescences are similar to those of A. artemisiifolia, but the male
inflorescence is longer (up to 20 cm) and the female heads are larger (2-4 mm in diameter). The
fruits are similar to those of A. artemisiifolia, with 4 to 8 small lateral thorns, but a little bigger
(4-8 mm long, 3-4 mm wide).
MEANS OF MOVEMENT AND DISPERSAL
Fruits of Ambrosia spp. are dispersed by birds, melting snow, waterways and strong winds.
Seeds of Ambrosia spp. are dispersed through exchanges of contaminated seed lots, forage and
fodder.
PATHWAYS
Contaminated seed and grain lots, forage and fodder, soil and growing media, soil attached to
plants.
DAMAGE
Ambrosia spp. are annual or perennial weeds which strongly compete with crop plants for water
and nutrients. They are very prolific (one plant may develop up to 100,000 seeds); seeds remain
viable for 5-14 years. They can seriously reduce yields of cereals and other field crops (e.g.
sunflower), and cause problems in harvesting. They releasee phytotoxic substances which affect
other plants. Their presence greatly reduces the fodder quality of meadows and pastures
(Ambrosia spp. are not palatable to livestock), and taints dairy products if cattle do feed on it. In
addition, their pollen is strongly allergenic in man (hay fever) and can cause dermatitis on
contact.
PHYTOSANITARY RISK
A. artemisiifolia is an introduced exotic pest for the EPPO region. It is a serious weed mainly
because of its prolific seed production. Once established in an area, even if relatively well
controlled on agricultural land, this weed can build up large populations on wasteland, and along
roadways and waterways. These are difficult to control and in particular give rise to human
health problems (hay fever, dermatitis). In North America, where it is native, A. artemisiifolia is
managed as part of the natural weed flora. It is, however, classed as a "noxious weed" in some
states of Australia. In the EPPO region, it is already fairly widespread in western Europe,
occurring more commonly in the warmer regions in the south. It is not generally regarded as a
problem weed for agriculture in the countries concerned. In Russia, it is estimated that it could
establish in areas up to approximately a latitude of 55°North (about the latitude of Moscow). As
it is currently only present in Krasnodar Territory in the far south, there is still a large area of
southern and central European Russia which remains uninfested. This weed appears of the list of
quarantine pests of the Russian Federation and is subject to internal phytosanitary measures to
prevent its spread. In the rest of the EPPO region, it is noteworthy that A. artemisiifolia is not
apparently present in Armenia or Georgia, in Bulgaria, Turkey or other eastern Mediterranean
countries, or in North Africa, and presents a risk to those areas. It is unlikely, on the other hand,
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that it would present a problem in those northern European countries where it has not yet been
found.
A. psilostachya, as a perennial, not producing such large quantities of seeds, has less potential for
spread and establishment in large populations. Its presence in some EPPO countries has not
drawn attention to it as invasive (but it is categorized as a noxious weed in Australia). A. trifida
is as common as A. artemisiifolia in North America; has rather similar biology and is also well
known for its allergenicity. However, it does not appear to have been as invasive as A.
artemisiifolia in the EPPO region.
PHYTOSANITARY MEASURES
The movement of agricultural seeds, grain, forage and fodder, infested with seeds of Ambrosia
spp. into pest-free areas should be restricted.
BIBLIOGRAPHY
Byfield AJ, Baytop A (1998) Three alien species new to the flora of Turkey. Turkish Journal of
Botany 22, 205-208.
Frankton C & Mulligan GA (1993) Weeds of Canada. Publication 948, Agriculture Canada,
Ottawa (CA).
Gudzinskas Z (1993) Genus Ambrosia in Lithuania. Thaiszia 3, 89-96.
Holm LG et al. (1991) A Geographical Atlas of World Weeds, Krieger, Malabar (US).
Karnkowski W (1999) Pest Risk Analysis on Ambrosia spp. for Poland. EPPO Document
99/7775.
Savotikov YuF, Smetnik AI (1995) Guide on pests, plant diseases and weeds of quarantine
significance for the Russian Federation. Arnika, Nizhnii Novgorod (in Russian).
Shutova NN (ed.) (1970) Guide on quarantine and other dangerous pests, diseases and weeds.
2nd edition. Kolos, Moscow (in Russian).
Vasic O (1988) Further expansion of the weed Ambrosia artemisiifolia L. in Serbia. Fragmenta
Herbologica Jugoslavica 17, 1-5.
Vasyutin AS, Smetnik AI, Mordkovich YaB, Zinchenko VN, Yudin BI, Smirnov SA,
Moskalenko GP, Shakhramanov IK, Maslyakov VYu (2001) Plant Quarantine in the Russian
Federation. Kolos, Moscow (in Russian).
Webb CJ (1987) Checklist of dicotyledons naturalised in New Zealand. 18. Asteraceae
(Compositae) subfamily Asteroideae. New Zealand Journal of Botany 25, 489-501.
Whitson TD et al. (1996) Weeds of the West. Western Society of Weed Science, Newark (US).
Entry date 2001-11
Fig. 1. Ambrosia artemisiifolia: 1) above-ground parts of the plant; 2) head of male flowers; 3)
male flower; 4) stamen; 5) female flower; 6) seedling; 7 and 8) fruits; 9)– seed.
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Fig. 2. Ambrosia psilostachya: 1) head of male flowers; 2) female flower; 3 and 4) fruits; 5)
rhizome; 6) above-ground parts of the plant; 7) leaf.
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Fig. 3. Ambrosia trifida: 1) – above-ground parts of the plant; 2) seedling; 3) head of male
flowers; 4) female flower; 5 and 6) fruits.