Impact of invasive herb allergy ‘underrated’

Scientists say the impact on human health across Europe of the invasive ragweed plant may be “seriously underestimated”.

Allergies caused by common ragweed (Ambrosia artemisiifolia) affect about 13.5 million people in Europe, according to their study.

This results in € 7.4 billion (£ 6.5 billion) in health costs per year.

But the authors say the plant could be controlled by a beetle, which is not native to Europe.

North American ambrosia leaf beetle (Ophraella communa) accidentally arrived in Europe in 2013. The beetle attacks ragweed foliage; Field studies in Italy have shown that the leaf beetle can reduce ragweed pollen by 82%.

Ambrosia also comes from North America and is now established in 30 countries in Europe, from Iberia and the Balkans to Scandinavia and the British Isles in the north.

Pollen from this invasive plant causes a variety of symptoms, from sneezing to itchy eyes. It also aggravates conditions like asthma and eczema.

Cautious optimism

Urs Schaffner, from CABI in Delémont, Switzerland, and his colleagues quantified the economic benefits of controlling ragweed using the leaf beetle.

Dr. Schaffner said: “Our study provides evidence that the impacts of common ragweed on human health and the economy so far are highly underestimated, but that biological control by Ophraella communa it could mitigate these impacts in parts of Europe. “

Using data from the European Pollen Monitoring Program, Dr. Schaffner and his colleagues mapped the total pollen from seasonal ragweed in Europe from 2004 to 2012, prior to the introduction of the beetle.

To reach a series of patients suffering from ragweed pollen allergy, the researchers compared their assessment at the European level with detailed health care data from south-eastern France.

They were then able to determine the overall economic costs of medical care to treat symptoms and other effects, such as lost time from work, from ragweed pollen.

But they also concluded that biological control of the ragweed plant using the leaf beetle could reduce the number of people with allergies from 13.5 million to approximately 11.2 million and reduce health costs from € 7.4 billion to € 6, 4 billion per year.

“Right now, biological control of ragweed is already happening in Italy,” said Dr. Schaffner.

“Any other country you want to use O. communa for the biological control of ragweed you would need to undergo a risk-benefit assessment and the national authorities should approve the use of this exotic insect for biological control in your country. “

Sunflower question

Dr. Schaffner said that a few years ago, Australia was considering the beetle for release there. But, he explained, “they discovered that under laboratory conditions O. communa it can complete its development in sunflowers and therefore rejected it as a safe biological control agent.

He told BBC News: “Then after the beetle accidentally entered China, the Chinese did a series of field studies and found no evidence that O. communa would actually attack sunflowers in field conditions. Our studies in northern Italy revealed very similar findings. “

Also, said lead author Professor Heinz Müller-Schärer, the beetle has coexisted with sunflower crops in the United States for decades. “We did not find a single report of damage from this sunflower beetle in the United States,” he said.

But the researchers want to run more tests before the beetle deliberately spreads.

The beetle is better adapted to warmer temperatures than the colder climates found in northern Europe. But there may be a way to avoid this problem.

“In northern Italy, weather conditions allow the beetle to complete four generations in one season, allowing the beetle to accumulate very high densities,” said Dr. Schaffner.

“In countries with a colder climate, this may not be possible; in those cases, mass releases of the beetle earlier in the year may be an option to increase the impact of the beetle on the grass.”

Professor Müller-Schärer told BBC News: “Furthermore, experiments are currently underway to select cold-adapted beetle strains that could then be released in cooler ragweed areas of Europe.”

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