Author
Lauréline FI Humair
l.humair@cabi.org
University of Neuchâtel and CABI
Delemont
Coauthors
Patrick Häfliger, CABI, Delemont, Switzerland
Ian A Knight, US Army Engineer Research and Development Center, Vicksburg, USA
Nate E Harms, US Army Engineer Research and Development Center, Lewisville, USA
Ryan Thum, Montana State University, Bozeman, USA
Philip RS Weyl, CABI, Delemont, Switzerland
Abstract
Two species within the Hydrocharitaceae are currently invading the Great Lakes region in northeastern North America: European frogbit, Hydrocharis morsus-ranae and water soldier, Stratiotes aloides. The introduction of both species is thought to originate from the Zurich Botanical Gardens. Currently there are no biological control agents available for either species, but through literature surveys, Hydrellia flies and Bagous weevils have been prioritised for further studies. Hydrellia flies are by far the most prevalent and widespread herbivores on both weed species, where during field surveys the flies have been found at nearly all sites. We currently assume H. albifrons to be specific on European frogbit and H. tarsata on water soldier. The Bagous weevils have been more challenging. So far, we identified five sites with B. puncticollis on European frogbit in eastern Europe and Sweden. In the laboratory, the adults feed heavily on the leaves, petioles, roots and turions from May to September. However, oviposition has only been recorded from two females collected in July/August, with larvae developing to adult only after being offered European frogbit turions. We have not yet located B. binodulus, the weevil expected, based on literature review, to be specific on water soldier. Both Bagous and Hydrellia species appear to be damaging to their hosts and would likely contribute to the management of both species in the invaded range if we determine they are host-specific.
Keywords
Hydrocharis morsus-ranae
Stratiotes aloides
biocontrol agent selection
agent biology
origin of weed
Highlights
Biocontrol agents can effectively be prioritised using literature surveys
Two potential agent groups identified for the biocontrol of Hydrocharitaceae in North America
Preliminary host tests allow for rapid assessment of agents prior to initiation of full programme