Prospects for the biological control of Iris pseudacorus L. (Iridaceae)

ABSTRACT

Native to Europe, North Africa and western Asia, Iris pseudacorus L. (Iridaceae) has invaded natural and human-modified wetlands worldwide. This species is considered a noxious weed in several countries including Argentina, South Africa and New Zealand. Its broad ecological tolerance, high resilience and reproductive potential make current mechanical and chemical control measures cost-ineffective, and biological control is considered a suitable alternative. In order to prioritise candidate biocontrol agents, a list of organisms reported to attack the plant within its native range has been assembled, and information about their host-range and damaging potential gathered from the literature. Furthermore, surveys for natural enemies of the plant were conducted in Belgium and northern Italy. The insect fauna associated with I. pseudacorus at the sites surveyed comprised mostly incidental visitors and polyphagous feeders, with the exception of the sawfly Rhadinoceraea micans Klug (Hymenoptera: Tenthredinidae), the seed weevil Mononychus punctumalbum Herbst (Coleoptera: Curculionidae), and the flea beetle Aphthona nonstriata Goeze (Coleoptera: Chrysomelidae). The potential of these species for biocontrol was evaluated, and A. nonstriata was given highest priority. A population of this species was imported to quarantine in South Africa, where it is currently undergoing host-specificity testing. Importation of the two remaining candidates is expected shortly. In conclusion, the prospects for the biological control of I. pseudacorus appear promising.

KEYWORDS:

• Yellow flag iris
• weed biological control
• native-range explorations
• agent selection
• invasive alien aquatic plants (IAAPs)
• North–South collaboration

Acknowledgements

The PhD project of G.M. is funded by a strategic basic research fellowship of the Research Foundation - Flanders (FWO). We thank the Vrije Universiteit Brussel (BAS 53 and BAS 42) and the Centre for Biological Control (Rhodes University) for logistic support. The authors would also like to thank nature conservators for providing some of the localities for sampling, and the entomologists of the Royal Belgian Institute of Natural Sciences (RBINS) for their help with insect identification. Iris pseudacorus biological control research in South Africa is funded through the Department of Environmental Affairs, Natural Resource Management Programmes (previously the Working for Water Programme). The South African Research Chairs Initiative of the Department of Science and Technology and the National Research Foundation of South Africa provided additional funding. Any opinion, finding, conclusion or recommendation expressed in this material is that of the authors, and the National Research Foundation does not accept any liability in this regard.

Disclosure statement

No potential conflict of interest was reported by the author(s).