CABI scientists suggest an accidentally introduced parasitoid could save box trees from ecological extinction

(Press-News.org) CABI scientists, who have published their research in the journal CABI Agriculture and Bioscience, suggest that an accidentally introduced parasitoid could help save wild box trees from ecological extinction.

The study highlights how an unidentified species of Eriborus (Hymenoptera: Ichneumonidae) could be used as a classical biological control for box tree moth Cydalima perspectalis (Lepidoptera: Crambidae) in Europe and North America.

Scientists, which included those from the Natural History Museum Basel, Switzerland, and Seoul National University in South Korea, say that high parasitism rates observed at several sites in Switzerland and Germany provide hope for protecting and saving wild box trees from the box tree moth pest.

Seriously threatening the survival of European wild Buxus spp.

Dr Marc Kenis, Head Risk Analysis and Invasion Ecology at CABI and an author of the paper, said, “This parasitoid likely arrived unintentionally some years ago with the importation of box trees from East Asia. Cydalima perspectalis is seriously threatening the survival of European wild Buxus spp., and very few control options are presently available.

“The presence of this Eriborus sp. opens new perspectives for classical biological control in all invaded areas, including North America, where the box tree moth has become a serious pest of ornamental Buxus spp. and could threaten native Buxus spp. in Mexico and the Caribbean.”

In spring 2024, an Eriborus sp. adult was caught in a botanical garden in Basel, Switzerland. To the scientists’ knowledge, this was the first detection of this parasitoid in Europe. In spring 2025, surveys were made to assess parasitism of C. perspectalis populations at various sites in North-Western Switzerland and at one site in South-Western Germany.

These surveys showed that the parasitoid is well established in the region, both in gardens and in wild box tree stands. Morphological observations and molecular analyses showed that the specimens found in Switzerland and Germany belong to the same species as specimens collected on C. perspectalis in South Korea. Parasitism was highest in wild stands, reaching 68% in Germany and 32% in Switzerland.

Eriborus sp. is only one of many cases of adventive biological control

The scientists argue that Eriborus sp. is only one of many cases of adventive biological control of invasive species through the non-intentional introduction of natural enemies from the area of origin of the pests.

In recent years, several similar cases have been observed in Europe and elsewhere. These include, among others, the introduction of Trissolcus japonicus, parasitoid of Halyomorpha halys, Leptopilina japonica, parasitoid of Drosophila suzukii, several parasitoids of invasive Eucalyptus pests, and even herbivores of invasive weeds such as the beetle Ophraella communa, an accidentally introduced biological control agent of Ambrosia artemisiifolia.

These natural enemies take advantage of the high abundance of their host in the invaded areas to establish themselves and spread. In the case of Eriborus sp., the parasitoid being the lytokous, a single cocoon or a parasitized larva imported on box trees may be sufficient for successful establishment.

Dr Lukas Seehausen, Research Scientist, Risk Analysis & Invasion Ecology at CABI and a co-author of the paper, said, “Eriborus sp. could be distributed elsewhere in Europe, Western Asia and North America but, before that, it remains to be seen whether the species is sufficiently specific to avoid non-target effects on native moths.

“The first non-target experiments conducted in quarantine are promising but the presence of Eriborus sp. in Swiss and German forests will allow us to assess its realized host range in nature, by collecting a large variety of caterpillar species present at the right places in the right moments to determine whether they are parasitized by Eriborus sp.”

Additional information

Main image: The box tree moth is a native moth throughout eastern Asia and feeds on boxwood (Credit: ©Friedrich Boehringer/via wikipedia - CC BY-SA 2.5).

Full paper reference

Marc Kenis, Seraina Klopfstein, Minho Lee, Seunghwan Lee, M. Lukas Seehausen, ‘Will an accidentally introduced parasitoid save European box trees?,’ 6 November 2025, CABI Agriculture and Bioscience, DOI: 10.1079/ab.2025.0081

The paper can be read open access here: https://www.cabidigitallibrary.org/doi/10.1079/ab.2025.0081

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