The beetles chew enough damage to the ragweed it can’t flower and spray its evil pollen into the air.
(CN) — A team of scientists revealed Tuesday that the humble leaf beetle holds the answers to relieving the suffering of over 2 million people in Europe — and millions more across the world — with allergies, while also saving billions in health care costs.
In the study published in the journal Nature Communications, lead author Urs Schaffner said the leaf beetle, scientific name Ophraella communa, can significantly reduce pollen from the common ragweed. Ragweed pollen causes a range of symptoms spanning from sneezing and itchy, watery eyes, to sinus pressure and poor sleep quality, and also aggravates conditions such as asthma and eczema.
Like most beetles, leaf beetles are round with shell-like wings that meet down the middle of their abdomen, short legs, and long antennae. They are called leaf miners as the larvae feast on the foliage, roots, and underground systems of plants while adults fly from plant to plant eating the leaves, flowers, and other plant parts. The Ophraella communa species is known to mainly feed on ragweeds, and has been the focus of many environmental studies of biological control around the world.
This interdisciplinary study is the first to quantify the economic benefits of biological control in Europe, and it sheds light on the true costs inflicted by invasive species like ragweed in Europe, which they argue are “most probably seriously underestimated.”
The team of scientists, from institutions including the University of Fribourg and ETH Zurich, Switzerland, the University of Worcester in the United Kingdom and Leiden University in the Netherlands, suggests that countries in the Balkan Peninsula — including Bulgaria, Romania and Serbia — will benefit most from the leaf beetle as a biological control.
In much of Europe, the common ragweed is considered an extremely invasive species and scientists warn its spread and impact will likely increase with rising temperatures brought on by climate change. The plant’s population exploded in the 1900s due to a contaminated import of grains and seeds from North America, and the invasion has continued annually ever since.
Before the leaf bug arrived by accident in 2013 and improved the invasive ragweed situation, an estimated 13.5 million people suffered from ragweed-induced allergies in Europe. The problem carries an economic price tag of $8 billion dollars each year.
Results from field studies in Italy have shown the leaf beetle can reduce pollen produced by the ragweed by 82%. Near Milan, where the hungry beetle was originally found, up to 100% of ragweed plants were attacked and the subsequent damage was drastic enough to prevent the plant from flowering — and therefore producing pollen.
“Our study provides evidence that the impacts of common ragweed on human health and the economy are so far highly underestimated, but that biological control by Ophraella communa might mitigate these impacts in parts of Europe,” said Schaffner. “We propose that future assessments of the economic impacts of Invasive Alien Species (IAS) should more thoroughly consider costs related to human health.”
The scientists gathered data from the European Pollen Monitoring Programme, interpolating data from 296 pollen monitoring sites across Europe, and used that information to map seasonal total ragweed pollen integrals in Europe during 2004 and 2012, just before the introduction of the leaf beetle.
Additionally, in order to validate the number of patients suffering from ragweed pollen allergies, the researchers compared their Europe-wide assessment with available health care data from the Rhône-Alpes region in southeastern France. They then included the cost of treatment and lost work time at the national level using purchasing power parity, which refers to the adjusted health expenditures per capita for 2015. From there, they were finally able to determine the overall economic costs of health care needed to treat the symptoms and other effects of ragweed pollen.
“We were not sure as first whether the leaf beetle was useful or harmful. Laboratory tests had shown that it was possible that it was harmful to sunflowers. However, field tests in China and Europe could not confirm this finding” said Heinz Müller-Schärer of the University of Fribourg.
Schaffner, Müller-Schärer and the other authors concluded “accurate information of policy and management about the impact of IAS on human health and the potential savings — due to the implementation of mitigation measures — is essential to ensure that reasonable resources are invested and actions coordinated in IAS management.”