Risk assessment to interpret the physiological host range of Hydrellia egeriae, a biocontrol agent for Egeria densa
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Egeria densa Planchon (Hydrocharitaceae) is a submerged macrophyte native to South America. It forms part of a new suite of invasive aquatic plants that has benefited from open nutrient-rich freshwater systems following the successful biological control of floating aquatic plants in South Africa. The specificity of the leaf-mining fly, Hydrellia egeriae Rodrigues (Diptera: Ephydridae) was tested, using traditional laboratory host-specificity testing (i.e., no-choice and paired choice). Only one non-target species, Lagarosiphon major Deeming (Hydrocharitaceae) supported larval development during pair-choice tests. In order to avoid the rejection of a safe and potentially effective agent, continuation (i.e., multiple generations) tests were conducted to measure the ability of the non-target species to nutritionally support a population indefinitely. None of these species could sustain a viable agent population for more than three generations. Laboratory host-specificity tests are limited as they exempt certain insect-host behaviours. To enhance the interpretation of host-specificity results, a risk assessment was conducted using agent preference (i.e., choice tests) and performance (i.e., choice and continuation tests) results. The feeding and reproductive risk that H. egeriae poses to non-target species is below 2%. Based on these findings, permission for its release in South Africa has been obtained.
KeywordsSubmerged aquatic weed Ephydridae Continuation test Multiple generation test
This research was funded through the Department of Environmental Affairs, Natural Resource Management Programme’s Working for Water programme. Further funding for this work was provided by the South African Research Chairs Initiative of the Department of Science and Technology and the National Research Foundation of South Africa. Thanks are extended to the editors and anonymous reviewers for their patient guidance and critical comments, which has improved the quality of this manuscript. Thanks are due to Dr Emily Strange, Dr Grant Martin and Dr Guillermo Cabrera Walsh for their assistance in this study.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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