Monitoring and control of the black twig borer

In recent years, southern Ticino has seen the emergence of several non-native bark beetle species of East Asian origin. Among these, the black twig borer (Xylosandrus compactus) represents a growing threat to the Botanical Garden of the Brissago Islands, where it infests numerous plants causing their wilting, dieback and, in the most severe cases, death. The damage results from the insects' boring activity inside twigs and from the spread of the fungi they carry, with which they maintain an obligate symbiotic relationship.
In order to monitor and contain the bark beetle population, the Botanical Garden staff is collaborating with researchers from the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) and the University of Freiburg. Ethanol and the essential oil of Laurus nobilis, one of the preferred host plants, are currently being tested individually and in combination in traps placed across the island. Should one of these attractants prove effective, mass trapping could be initiated to reduce the resident population. In parallel, trials are planned with specific fungal species capable of interfering with the growth of the beetle's symbiotic fungi, thereby inhibiting its development.
Both the attractants used in the traps and the fungi applied to the plants pose no risk whatsoever to visitors of the Botanical Garden.

Collaborators
Prof. Dr. Eckehard Brockerhoff, eckehard.brockerhoff(at)wsl.ch¹
Dr. Simon Blaser, simon.blaser(at)wsl.ch¹
Dr. Ludwig Beenken, ludwig.beenken(at)wsl.ch¹
Arvid Homola, arvid.homola(at)students.uni-freiburg.de²
José Ribeiro-Correia, jose.ribeiro(at)wsl.ch^{1, 3}
Dr. Alessio Maccagni, alessio.maccagni(at)ti.ch⁴

Project duration
2025 – 2026

Project status
Ongoing

Financial support
Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Repubblica e Cantone Ticino (Isole di Brissago), Federal Office for the Environment (FOEN)

¹Swiss Federal Institute for Forest, Snow and Landscape Research (Birmensdorf, Switzerland)
²University of Freiburg (Freiburg, Germany)
³Swiss Federal Institute of Technology Zurich (Zurich, Switzerland)
⁴Repubblica e Cantone Ticino, Giardino botanico cantonale delle Isole di Brissago (Isole di Brissago, Switzerland)