Weeds as potential quarantine pests
The Panel on Phytosanitary Measures is currently discussing the potential quarantine status of weeds, the following species were proposed as potential candidates and are therefore added to the EPPO Alert List: Ambrosia artemisiifolia, Acroptilon repens, Striga lutea, S. hermonthica and S. gesnerioides.
Ambrosia artemisiifolia (Asteraceae) - common ragweed
Why
The Panel on Phytosanitary Measures is currently discussing the potential quarantine status of weeds, and Ambrosia artemisiifolia was retained as a potential candidate.
Where
It is native to North America and has spread from there to many other areas in the world (except perhaps Africa).
Europe: Austria, Belgium, Croatia, Czechia, France, Germany, Hungary, Italy, Lithuania, Luxemburg, Moldova, Poland, Portugal, Romania, Russia (Krasnodar territory), Slovakia, Sweden, Switzerland, Turkey, UK, Ukraine, Yugoslavia (at least Serbia).
Asia: Azerbaijan, China (Yangtze river valley, Liaoning), Japan, Kazakhstan, India, Korea, Russia (Primorski territory), Taiwan, Turkey.
Africa: Mauritius.
North America: Canada (in all provinces, but most common in southern Quebec and Ontario, very rare in British Columbia and Newfoundland, uncommon in prairie provinces and provinces of the Atlantic coast), Mexico, USA (eastern, north central states, Hawaii).
Central America & Caribbean: Cuba, Guadeloupe, Guatemala, Jamaica, Martinique.
South America: Argentina, Bolivia, Brazil, Chile, Colombia, Paraguay, Peru, Uruguay.
Oceania: Australia, New Zealand.
On which crops
A. artemisiifolia can infest practically all field crops (cereals, maize, soybean, sunflower, rootcrops, etc.), meadows, pastures, orchards and vineyards, and also rangeland. However, it is commonest along waterways, roads, railways and in wasteland.
Dissemination
Fruits of A. artemisiifolia are dispersed by birds, melting snow, waterways and strong winds. Seeds of A. artemisiifolia are dispersed through exchanges of contaminated seed lots, forage and fodder.
Damage
A. artemisiifolia is an annual weed which competes strongly with crop plants for water and nutrients. It is very prolific (one plant may develop 30,000 - 40,000 seeds and up to 100,000); seeds remain viable for 5-14 years). It can seriously reduce yields of cereals and other field crops (e.g. sunflower), and causes problems in harvesting. Its presence greatly reduces fodder quality of meadows and pastures (A. artemisiifolia is not palatable to livestock), and taints diary products if cattle do feed on it. In addition, its pollen is strongly allergenic in man (hay fever) and can cause dermatitis on contact.
Pathway
Contaminated seed lots, forage and fodder, soil and growing media, soil attached to plants.
Possible risks
A. artemisiifolia is a serious weed mainly because of its prolific seed production. It has already shown a great potential for spread and it is regularly found on consignments of seeds. Once established in an area, it is difficult to control. A. artemisiifolia is apparently not present in all countries of the EPPO region, and it could present a risk to countries where it is still absent (except perhaps in northern countries where low temperatures may prevent its development).
Acroptilon repens (Asteraceae) - Russian knapweed, creeping knapweed
Why: The Panel on Phytosanitary Measures is currently discussing the potential quarantine status of weeds, and Acroptilon repens was retained as a potential candidate.
Where: A. repens is native to Central Asia and has spread from there to many other areas.
Europe: Russia (Volgograd, Rostov, Saratov and Orenburg provinces, Stavropol territory, Kalmykia), Ukraine (south).
Asia: Afghanistan, Armenia, China (eastern), Georgia (north), India, Iraq, Iran, Kazakhstan, Kyrghystan, Mongolia, Syria, Tajikistan, Turkey, Turkmenistan, Uzbekistan.
Africa: South Africa.
North America: Canada (widely distributed in Alberta, Manitoba, Satskatchewan, common in British Columbia, present in Ontario), USA (most common in the semi-arid western states, present in 21 states).
South America: Argentina.
Central America & Caribbean: Trinidad.
Oceania: Australia.
On which crops: All sown crops may be infested, but A. repens is confined to areas with a warm, dry climate, with annual precipitation up to 400 mm. It is not a weed of intensive agriculture in temperate climates or under irrigation. Its persistence and colonial habit can also cause problems in orchards, vineyards, pastures or roadsides.
Damage: A. repens is a perennial weed, reproducing by seeds and by rhizomes which strongly compete with crops for water and nutrients. Plants are poisonous for many animals (especially horses, but not sheep and goats).
Dissemination: A. repens seeds are carried with harvested seeds of many herbaceous crops, particularly cereals, and also with hay and straw. Locally, the dried fruiting heads can be carried from infested fields by water courses.
Pathway: Contaminated seed lots (especially cereals), fodder (especially hay and straw), soil and growing media, soil attached to plants.
Possible risks: A. repens is an invasive weed which continues to spread in areas where it occurs. Its control is difficult (cultural practices are not effective, chemical control is difficult). However, in the EPPO region most areas are unsuitable for its development (i.e. northern and western Europe). It could present a risk for the Mediterranean region and Central Europe.
Striga spp. (Scrophulariaceae) - witchweeds
Why: The Panel on Phytosanitary Measures is currently discussing the potential quarantine status of weeds, and Striga lutea, S. hermonthica and S. gesnerioides were retained as potential candidates.
Where:
Striga lutea
Asia: Bangladesh, Cambodia, China, India, Indonesia, Japan, Malaysia, Myanmar, Oman, Pakistan, Philippines, Saudi Arabia, Singapore, Sri Lanka, Thailand, Viet Nam.
Africa: Angola, Benin, Botswana, Burkina Faso, Cameroon, Comoros, Congo, Côte d'Ivoire, Egypt, Ethiopia, Ghana, Guinea, Guinea-Bissau, Kenya, Lesotho, Liberia, Madagascar, Malawi, Mali, Mauritius, Mozambique, Namibia, Nigeria, Réunion, Rwanda, Senegal, Seychelles, Sierra Leone, Sudan, South Africa, Swaziland, Tanzania, Togo, Uganda, Zaire, Zambia, Zimbabwe.
North America: USA (North Carolina, South Carolina).
Oceania: Australia, New Zealand, Papua New Guinea.
Striga hermonthica
Asia: Cambodia, Saudi Arabia, Yemen.
Africa: Angola, Benin, Burkina Faso, Burundi, Cameroon, Central African Republic, Chad, Congo, Côte d'Ivoire, Egypt, Ethiopia, Gambia, Ghana, Guinea, Guinea-Bissau, Kenya, Madagascar, Mali, Mauritania, Morocco, Mozambique, Namibia, Niger, Nigeria, Rwanda, Senegal, South Africa, Sudan, Swaziland, Tanzania, Togo, Uganda, Zaire, Zambia, Zimbabwe.
Striga gesnerioides
Asia: Cambodia, India, Japan, Saudi Arabia, Sri Lanka, Yemen.
Africa: Benin, Botswana, Burkina Faso, Burundi, Cameroon, Cape Verde, Chad, Congo, Egypt, Ethiopia, Ghana, Guinea, Kenya, Malawi, Mali, Mauritania, Morocco, Mozambique, Niger, Nigeria, Senegal, South Africa, Sudan, Togo, Zaire, Zambia, Zimbabwe.
North America: USA (Florida)
Oceania: Australia
On which crops: Striga lutea: Poaceae, especially maize, sorghum, rice and sugarcane, but also sometimes on wheat and barley. Wild plants and weeds of the following genera: Digitaria, Echinochloa, Imperata, Paspalum, Pennisetum, Sorghum.
Striga hermonthica: Poaceae, especially sorghum but also maize, Panicum, Setaria, sugarcane.
Striga gesnerioides: especially on cowpea and tobacco. Also on numerous plants of the Poaceae, Fabaceae and Convolvulaceae.
Damage: Striga lutea and S. hermonthica are annual hemi-parasites of monocotyledones, S. gesnerioides is a full parasite of dicotyledons. Greatest damage is done in the first month of vegetative growth, when the fully parasitic young witchweeds have not yet emerged. The host plant wilts, its growth is stunted and it may shrivel and die. Yield losses can reach significant levels (up to 100%).
Dissemination: As seeds are very small they are easily dispersed by wind, water, animals, etc. Seeds can also contaminate harvested products, or be moved in soil by machinery etc. Seeds are very difficult to detect as contaminants of seed lots (microscopic examination is needed).
Pathway: Contaminated seed lots, fodder, soil and growing media, soil attached to plants.
Possible risks: Witchweeds are essentially tropical pests, but S. lutea has been found in North and South Carolina (US) and has been able to maintain populations. The potential for establishment in the EPPO region of Striga spp. remains unclear. Regions with a relatively mild dry winter (Black Sea area, eastern Mediterranean region, North Africa) may be suitable for weed development. Chemical control is available, and research is being done on the use of resistant cultivars.
Sources
Draft EPPO Data Sheet.
Pest Risk Analysis on Ambrosia spp. for Poland prepared by W. Karnkowski, 1999.
Byfield, A.J.; Baytop, A.; (1998) Three alien species new to the flora of Turkey. Turkish Journal of botany, 22(3), 205-208.
Djurkic, M.; Knezevic, M.; Ostojic, Z. (1997) Effect of rimsulfuron application on weeds in maize inbred lines in Croatia. Cereal Research Communication, 25(2), 203-209.
Frankton, C;; Mulligan, G.A. (1993) Weeds of Canada, Publication 948, Agriculture Canada, 217 pp.
Gudzinskas, Z. (1993) Genus Ambrosia L. (Asteraceae) in Lithuania. Thaiszia, 3(1), 89-96.
Holm, L.G.; Pancho, J.V.; Hergerger, J.P.; Plucknett, D.L. (1991) A geographical Atlas of world weeds, Krieger publishing Company, Malabar, Florida (US), 391 pp.
Hsu, C.C. (1973) Some noteworthy plants found in Taiwan. Taiwania, 18, 62-72.
Sahoo, U.K. (1998) Effect of depth and duration of burial on seed viability and dormancy of four annual weeds. Annals of Agricultural Research, 19(3), 304-310.
Vasic, O. (1988) Further expansion of the weed Ambrosia artemisiifolia L. in Serbia. Fragmenta Herbologica Jugoslavica, 17(1-2), 1-5.
Wang Zhirong (chief editor) (1990) Farmland weeds in China. A collection of coloured illustrative plates. Agricultural Publishing House, China, 506 pp.
Webb, C.J. (1987) Checklist of dicotyledons naturalised in New Zealand. 18. Asteraceae (Compositae) subfamily Asteroideae. New Zealand Journal of Botany, 25(4), 489-501.
EPPO RS 2000/002
Draft EPPO Data Sheet.
Frankton, C;; Mulligan, G.A. (1993) Weeds of Canada, Publication 948, Agriculture Canada, 217 pp.
Holm, L.G.; Pancho, J.V.; Hergerger, J.P.; Plucknett, D.L. (1991) A geographical Atlas of world weeds, Krieger publishing Company, Malabar, Florida (US), 391 pp.
Reed, C.F. (1977) Economically imported foreign weeds. Potential problems in the United States, Agriculture Handbook no. 498, USDA, Washington, USA, 746 pp.
INTERNET
Acroptilon repens. Southwest exotic plant mapping program.
http://www.usgs.edu/swemp/Info-pages/plants/Acroptilon/Russianknapweed.html
Element stewardship abstract for Acroptilon repens. the nature Conservancy.
http://tncweeds.ucdavis.edu/esadocs/documnts/acrorep.html
North American Russian knapweed (Centaurea repens) inventory.
http://w3.uwyo.edu/~caps/rkinventory/rkinv.htm
Draft EPPO Data Sheet.
Banda, E.A.K.; Morris, B. (1985) Common weeds of Malawi. Montfort Press, Malawi, 176 pp.
CABI Crop Protection Compendium, 1999.
Ivens, G.W. (1993) East African weeds and their control (new edition). Oxford university Press, Nairobi, 288 pp.
Holm, L.G.; Pancho, J.V.; Hergerger, J.P.; Plucknett, D.L. (1991) A geographical Atlas of world weeds, Krieger publishing Company, Malabar, Florida (US), 391 pp.
Parker, C.; Riches, C.R. (1993) Parasitic weeds of the world: biology and control. CABI, Wallingford, UK, 332 pp.