Action Plan to Combat Ambrosia

Background and Goals

Ambrosia artemisiifolia, known as Common Ragweed or Hay Fever Weed, is a native plant of North America. There is a wealth of scientific knowledge available from various European countries concerning the biology of the species, its distribution, its pollen flight characteristics and its effects on human health as well as agriculture and conservation, but there are still gaps in this knowledge with respect to Germany.

Objectives: The action plan to combat Ambrosia includes monitoring its occurrence, measures to prevent its introduction and spread, and publicizing the dangers and possible countermeasures against this highly invasive neophyte with its strongly allergenic pollen.

Content time

Research area/region

  • Germany

Steps in the process of adaptation to climate change

Step 1: Understand and describe climate change

Approach and results 

The project refers to no specific climate scenario.

Parameter (climate signals)
  • Altered rainfall patterns
  • Higher average temperatures

Step 2a: Identify and assess risks - climate effects and impact

Approach and results 

It is known that, due to its late flowering, Ambrosia artemisiifolia will not develop mature seeds in colder climates, so that the species cannot establish itself there. However, reliable information on the precise climatic conditions under which seed maturation does occur is missing. This information is important for pinpointing current habitat boundaries, as well as for predicting the future development of these boundaries in the course of the climate change. We are also missing information on the adaptability of the species to other climates.

The spread of Ambrosia artemisiifolia along roadways and through earth transport during construction work is a further problem that needs to be addressed. Populations recently observed in the Lower Lausitz that have exhibited a change in the phenology of the plant give rise to a concern that Ambrosia may be adaptable enough to be able to establish itself in less congenial climates. This shifts the focus of the plan onto the prevention of the introduction and spread of the plant.

Step 3: Develop and compare measures

Measures and/or strategies 

Measures to limit the further spread of ragweed should include the measures to combat its further introduction and dissemination, for example in bird seed and other unground grain feed, or by agricultural machinery and contaminated soil.

Measures to combat existing populations, with the aim of preventing or reducing the further propagation of the plant, are carried out in varying degrees in different regions. It has been shown that the success of these actions depends less on the choice of method than on the consistent implementation of a chosen measure. As ragweed occurs in most German states on roadsides, in private and public greens and in ruderal areas (disturbed lands), mechanical methods such as uprooting and mowing are applied for the most part.

Step 4: Plan and implement measures

Measures and/or strategies 

A pest organism in Germany must be officially registered. This is to warn other countries and Member States of the European Union , so that measures to prevent the spread can be made. The focus is on so-called "potential quarantine organism" that occur at the first time, might establish and cause significant economic and ecological damage.

Step 5: Watch and evaluate adaptation (monitoring and evaluation)

Approach, objective and results of the monitoring and/or evaluation 

The Julius Kühn Institute (JKI) has created a web atlas (WAtSon) for reporting pests for this purpose. This is an electronic system for reporting and monitoring Ambrosia occurrences in Germany, and includes a cartographic representation of the incidences reported.


Funding / Financing 

Federal Ministry of Food, Agriculture and Consumer Protection (BMELV)

Project management 

Julius Kühn-Institut in Braunschweig (JKI)


In cooperation with the German federal states and municipalities


JKI - Julius Kühn-Institut, Bundesforschungsinstitut für Kulturpflanzen
Messeweg 11-12
D-38104 Braunschweig

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Fields of action:
 human health and care