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Invasive weed poses nuisance to allergy sufferers

Even though the spread of ambrosia (commonly known as ragweed) is limited in Denmark, it extends the pollen season for allergy sufferers. Researchers at Aarhus University are working as part of an EU project to combat the plant as best possible.

[Translate to English:] Forskere ved Aarhus Universitet arbejder på at bekæmpe ukrudtsplanten ambrosia, der udgør et stigende problem for allergikere i Europa. Foto: AU

Several countries in central Europe are all too familiar with ambrosia, which is a real pest for allergy sufferers. Ambrosia is a highly effective spreader of very fine, small pollen particles, which are highly allergenic. One weed can spread about 35 million pollen particles in a year, and it only takes 10 pollen particles per cubic meter air to induce hayfever in those who are allergic.


Ambrosia is not yet particularly common in Denmark and only poses a minor problem, but the plant is expected to become more prevalent as a result of increasingly mild weather in Denmark. This is something that researchers from Aarhus University wish to prevent. They are working, along with Germany, Austria, Hungary and Slovenia, on new methods to combat the plant as part of the EU project HALT AMBROSIA.


- We are, in one experiment, looking at the effect of fatty acids and acetic acid on ambrosia. We are also investigating at which stage of the plant's development it is most vulnerable. We have selected two stages. One where the plants are small and have three or four leaves and one where they are about 10 cm high and have sprouted some side shoots, explains senior scientist Solvejg K. Mathiassen from Aarhus University. She goes on to say:


- We are also carrying out another experiment where we examine a combination of cutting down the plants and subsequently treating them with herbicides. This is due to ambrosia often being encountered on building sites and areas of bare soil where the plant suddenly appears and where it can develop a very dense plant cover. In these situations it is customary to simply cut the plants down. It is possible however, that the plants would be better suppressed or exterminated by subsequently spraying with herbicides.


In the video below (only available in Danish), which explains the challenges posed by the ambrosia plant, Solvejg K. Mathiassen explains that ambrosia has primarily arrived in Denmark via birdseed balls, which Danes hang up in their gardens for birds. Ambrosia has a strong growth and is capable of competing with crops for water, light and nutrients. It rarely occurs as a weed in fields at the moment, but there is a strong focus on the spread of ambrosia, due to it extending the pollen season.


- Ambrosia spreads its pollen from some time at the end of July and on until the middle of September. Which is to say, this pollen appears at a time when sufferers of grass pollen allergy have finished their worst period as well as those suffering from birch pollen allergy. Ambrosia thus extends the season for allergy sufferers and can therefore be seen as a health issue. This is why people are very determined to combat it, explains Solvejg K. Mathiassen.



Further information: Senior scientist Solvejg K. Mathiassen, Department of Agroecology, phone: +45 8715 8194, email: solvejg.mathiassen@agrsci.dk

Facts: The EU project “HALT AMBROSIA. Complex research on methods to halt the Ambrosia invasion in Europe” was started in January 2011 and runs until 31 December 2013. In addition to Aarhus University, other participants are the Julius Kühn-institut, Germany, Universität für Bodenkultur, Austria, Academy of Sciences, Plant Protection Institute, Hungary, Kaposvar University, Hungary, and the Agricultural Institute of Slovenia.