Heinz Müller-Schärer¹, Yan Sun¹, Maria Litto¹, Sarah Bouchemousse¹, Suzanne Lommen¹ Benno Augustinus^1,2 and Urs Schaffner²

¹Department of Biology, University of Fribourg, CH-1700 Fribourg, Switzerland
²CABI, CH-2700 Delémont, Switzerland

e-mail: heinz.mueller@unifr.ch

Balancing benefits with risks is key in developing a successful biological control program. In 2013, we were confronted with the accidental introduction of the North American native ragweed leaf beetle (Ophraella communa) into Europe, which needed an urgent decision on how to respond to this unforeseen arrival of an oligophagous insect. We immediately reacted to this event by our newly formed COST-SMARTER consortium composed of specialists in weed and invasive species management, ecology, aerobiology, allergology and economics.

Firstly, we will summarize our findings on the beetle’s potential benefits, ranging from its impact on ragweed performance, demography, spread, aerial pollen concentrations up to reducing health cost. We will further present our results on the risks of the beetle for non-host plants in Europe. So far, we detected no impact on sunflower, probably because the window of vulnerability of this crop does not coincide with high beetle densities at the end of the growing season. The same holds true for taxonomically closely related ornamental and endangered native plant species.

Secondly and in view of improving predictions for future long-term benefits and risks of this potential biological control program, we initiated a novel experimental evolutionary approach to assess the beetle’s potential to select for resistant/tolerant ragweed populations (study 1), as well as the beetle’s potential for evolutionary adaptation to novel biotic (host plants) and abiotic (colder temperature for the yet unsuitable habitats in Central Europe, and considering climate change) conditions (study 2), using next generation sequencing and bioassay approaches. We will present the 2017 and 2018 results of both studies from our demographic, phenotyping, as well as genomic analyses, of both the experimental ragweed (over two generations) and beetle (over six generations) populations.

This is the first attempt to rigorously and simultaneously assess the evolvability of a biological control agent with its target weed.

Lommen S. T. E., Jongejans E., Melinda Leitsch-Vitalos M., Tokarska-Guzik B., Zalai M., Müller-Schärer H. & Gerhard Karrer G. (2018) Time to cut: population models reveal how to mow invasive common ragweed cost-effectively. NeoBiota 39: 53–78.
Mouttet R., Augustinus B., Bonini M., Chauvel B., Gachet E., Le Bourgeois T., Müller-Schärer H., Thibaudon M. & Schaffner U. (2018) Estimating economic benefits of expected biological control of an allergenic weed: a case study for Ophraella communa against Ambrosia artemisiifolia in southeastern France. Bas. Appl. Ecol. 33: 14–24.