Invasives Blog


One in four people in Europe suffer from hay fever, affecting the quality of life of millions. The average cost of hay fever related diseases amounts to around €600 per patient per year from treatment costs and lost time working.

One of the worst offending invasive plants for hay fever sufferers is the North American common ragweed Ambrosia artemisiifolia.

Since ragweed was first discovered in Europe in the 19th century it has become widespread with hotspots in the Balkans, northern Italy and the Rhône Valley in southeastern France.

Where ragweed grows, 10–60% of people exposed to its pollen develop some form of allergic reaction costing the European economy €4.5 billion a year.

Tackling this invasive weed is important for the health of Europe’s citizens and its economy. Coming up with a solution is therefore crucial.

Biocontrol could provide the solution. In a recent study published in Basic and Applied Ecology, the authors, including CABI’s Urs Schaffner and Benno Augustinus, estimate cost savings of €5.2–6.8M annually if biocontrol is used to reduce pollen production of ragweed in the Rhône Valley area.

The biocontrol method in questions is the leaf beetle Ophraella communa already controlling ragweed in the Milan area of northern Italy. It feeds off ragweed causing defoliation significantly reducing pollen production and hampering its ability to reproduce.

Ragweed and beetle

Leaf beetle Ophraella communa eating common ragweed, photo credit Heinz Müller-Schärer

Originally also from North America, the leaf beetle was found to be accidentally introduced to Italy and Switzerland in 2013. It is now considered a primary biocontrol candidate for suppressing ragweed populations in the hotspot areas of Europe.

The leaf beetle has successfully reduced concentrations of ragweed pollen by approximately 86% in the Milan area. The study believes similar success can be achieved in the Rhône Valley due to its similar climate and landscape.

Vital for securing investment, and ultimately the success of any biocontrol agent, is proving that the benefits outweigh the costs. Detailed economic data on the health costs caused by common ragweed are available for the Rhône Valley region. The study shows that in this region for every €1 spent on researching and releasing the leaf beetle, approximately €90 will be saved from the health benefits associated with less ragweed pollen in the air.


Next steps from the study call for an investment of public funds in a comprehensive risk assessment of the leaf beetle in Europe and its wide-scale release, dependent on the outcomes of the risk assessment.

The issue of invasive weed species in Europe is becoming ever more prescient due to a variety of factors including climate change and increased pathways for species introduction through international trade and travel.

In August 2018, some of the world’s leading scientists debated how best to tackle invasive weed species at the XV International Symposium on Biological Control of Weeds in Engelberg, Switzerland, co-organised by CABI and the University of Fribourg (see video below).

Hay fever sufferers in Italy are already breathing a sigh of relief thanks to the leaf beetle. Ensuring many more people in Europe benefit from the leaf beetle and other biocontrol projects drives CABI and others to continue researching how best to tackle the problems of invasive weeds now and into the future.

Click for information on CABI’s project on Integrated Weed Management in Europe



  1. Teddy Searight on 19th September 2018 at 08:53

    Reblogged this on The CABI Blog.

  2. […] continent. The average cost of hay fever related diseases to the European economy is estimated at €4.5 billion a year due to treatment costs and lost time working. Since ragweed was first discovered in Europe in the […]

Leave a Reply

Related News & Blogs

Training on mass production of entomopathogenic nematodes for biological control of invasive insect pests

A team of global experts in the production of biocontrol agent provided a practical training on the mass culture of entomopathogenic nematodes at the Biocontrol Agent Facility of Rwanda Agriculture and Animal Resource Development Board (RAB), writes Dr…

20 December 2023