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Abstract
Ceutorhynchus scrobicollis is a root-crown mining weevil proposed for release as biological control agent of Alliaria petiolata (Brassicaceae, Thlaspideae), a European biennial herb, currently invading temperate North America. Using a combination of laboratory, common garden and fieldwork we studied biology, ecology and host range of C. scrobicollis, a univoltine species that oviposits and develops in A. petiolata rosettes in fall and spring. Individual C. scrobicollis can be long-lived (>2 years) and females show a second oviposition period. Weevils did not attack any of 31 test plant species outside the Brassicaceae. Within the Brassicaceae, five species allowed complete larval development under no-choice conditions. In subsequent choice tests, three of these five species (Nasturtium officinale, Peltaria alliacea and Thlaspi arvense; which are of European origin) were attacked. North American Rorippa sinuata was the only native species to be attacked by C. scrobicollis and only under no-choice conditions. Results of subsequent impact experiments showed that C. scrobicollis attack changed plant architecture but had no effect on overall plant vigour and reproductive output of R. sinuata, suggesting lack of impact on demography or population dynamics. A petition for field release of C. scrobicollis in North America has been submitted.
Acknowledgements
We thank David Evans, Elisabeth Gault, Nathalia Guazzone, Léonore Lovis, Jessica McKenney, Frank Oberholzer, Hélène Schneider, Marion Zuefle and Magali Rohner for their lab and field assistance and Florence Willemin and Christian Leschenne who propagated the A. petiolata and test plants (all CABI E-CH). Test plant seeds and cions were obtained with the assistance of Richerd Dunbar, Robert Wiedenmann and Judy Parrish. Lutz Behne (Entomological Institute, Eberswalde, Germany) confirmed the identification of Ceutorhynchus scrobicollis and Erasmus Haeselbarth (Zoologische Staatssammlung, München, Germany) identified adult parasitoids reared from C. scrobicollis. Funding for this work was provided through Hennepin Parks (Minnesota), Illinois Natural History Survey, Illinois State Nature Preserves Comission, Illinois and Indiana Native Plant Societies, Indiana Division of Nature Preserves, Kentucky State Nature Preserves Comission, Minnesota Scientific and Natural Areas, Strategic Environmental Research and Development Program, US Department of Defence, Project CS 1146, USDA APHIS Eastern Region, USDA Forest Service, US Fish and Wildlife Service and Wisconsin Department of Natural Resources.
