EWRS logo

European Weed Research Society
Invasive Plants

Leaflet titled: «Common Ragweed: Menace for Public Health and Biodiversity»:
- in English (pdf, 2.4 Mb)
- in Esperanto (pdf, 2.6 Mb)
- in French (pdf, 664 Kb)
- in German (pdf, 661 Kb)
- in Italian (pdf, 655 Kb)
- in Portuguese (pdf, 2.4 Mb)
Click here to see photos of ragweed (Ambrosia artemisiifolia)  


Common Ragweed (Ambrosia artemisiifolia L.)

Call for Action - Ragweed

A problem of national and international importance – the invasion of Common Ragweed (Ambrosia artemisiifolia L.) in Europe

Common Ragweed, which is native to North America, has highly allergenic pollen which causes allergic rhinitis and severe asthma in over 20% of the population of affected areas. These health problems cause losses of work time and costs of medical visits and medication. Furthermore, projected climatic change will exacerbate the current situation and lead to more widespread health problems in the near future. In agriculture, the plant is also a significant agricultural pest, causing yield loss in many crops.

Adequate management of this weed will require the concentrated and continued development and application of control measures over a long period.

For example :
SWITZERLAND (beginning of invasion) has adapted its ordinance of plant protection in 2006 and declared an obligation to control Ragweed. This enables agricultural extension services to enforce permanently an effective ragweed control in agricultural fields.

In HUNGARY (highly infested country) the “Interministerial Commission for a Ragweedfree Hungary” of eight Hungarian ministries created a legal base for obligation of control and now cooperates with non-governmental organizations: control is obligatory for each land owner before the flowering period ! Belated land owners will be fined with 20’000 to 5 million HUF.

This Call for Action may help YOU to motivate responsible authorities in YOUR COUNTRY for enabling long term ragweed control on a legal basis. Please download the PDF files
- Call for action (ambrosia_call_for_action.pdf (195 Kb))
- Motivation (ambrosia_motivation.pdf (400 Kb))

Please send an e-mail to the coordinator if you need further information.

Control Strategy for regions at the beginning of an invasion:

Uproot and destroy plants before pollen and seed production!

Everybody can help to reduce ragweed populations effectively.
  • 1 – 20 plants found: pull it completely out and give it to the household waste
  • no composting of flowering plants.
  • > 20 plants found: control measures by specialists
  • Check the site for ragweed in the following years
  • In any case (for Switzerland): inform immediately the landowner and the local authorities.

Control Strategy for highly infested regions:

Uproot and destroy plants before the beginning of pollen and seed production

Efficacy of various herbicides

Herbicide efficacy was tested by the Research Station Agroscope ACW in Nyon, Switzerland during several years in an infested field, but without crop.
In a greenhouse trial, Ambrosia plants in pots were treated with several herbicides and at several growth stages.

Effect of herbicides on viability of grains

In a field trial, Ambrosia plants were treated shortly after oilseed rape harvest. The upper part of the taller plants might have been cut by the combine harvester in one replication. The other replication was placed at the adjacent field boundaries. Herbicide application was at the beginning of fruit development. We from ACW randomly collected side branches containing seed grains five weeks after application.

Combination of cut and herbicide

The first experiences in Ambrosia control showed that one measure might not be sufficient to disrupt the life cycle. A field trial was conducted in 2006 to search the best method to prevent production of viable seeds with a combination of cut and herbicide.

Disrupting the life cycle in one cut?

A three-year field trial was carried out to search for the best date for cutting Ambrosia. The “best” date was defined as that date when uncut Ambrosia plants would not have produced mature grains yet and the growing side branches of to date cut Ambrosia would not be able to produce mature grains.

Further information:

Christian Bohren, Research Station Agroscope ACW
Email: christian.bohren@acw.admin.ch
February, 2008