Context |
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There was an urgent and immediate need to control high density populations of GWSS in French Polynesia. By reducing population densities many problems, both actual (human nuisance, and continued range expansion) and potential (widespread vectoring of X. fasitidiosa) would be mitigated. A review of potential control options was commissioned in 2003 by the French Polynesian Ministry of Agriculture. The conclusion reached by Ministry officials was that biological control potentially offered the most effective and permanent management solution for GWSS. In 2004, a classical biological control program using the mymarid egg parasitoid Gonatocerus ashmeadi was given approval. This biological control program was initiated by the University of California (Berkeley and Riverside campuses) via the University of California Richard B. Gump South Pacific Research Station on Moorea. An alliance between University of California personnel and scientists with the French Polynesian Agricultural Research and Plant Protection Departments guided the development of the GWSS biological control program. |
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- Objectives of the biocontrol program |
The objective of this biological control program was to significantly reduce GWSS populations in Tahiti and Moorea, using a host specific natural enemy, the egg parasitoïd Gonatocerus ashmeadi, and to assess beforehand the potential impact of the parasitoïd on the native insect fauna of French Polynesia. |
- Release protocol |
| A rigorous experimental protocol was designed to evaluate the impact of the biological control program against GWSS. This evaluation program contained three majors components. |
| 1) Preliminary studies |
Preliminary studies of the pest (e.g., quantification of population densities over time, distribution, host plant use, and nuisance problems), of the control agent (e.g., host specificity and mass rearing constraints) and determination of the risk posed by G. ashmeadi to non target native fauna (i.e., collateral risk of attack and identification of potential species threatened by G. ashmeadi), were considered indispensable steps before the introduction of an exotic natural enemy into French Polynesia could be made. These analyses provided data for stakeholders, environmentalists, the public, and politicians useful information to assist with decisions to safely authorize the introduction of G. ashmeadi into French Polynesia. |
| 2) Release of the parasitoïd |
The release steps for G. ashmeadi involved mass rearing of the parasitoïd in quarantine, and development of a release strategy to optimize the likelihood of establishment, spread, and impact against the pest. |
| 3) Monitoring the impact of the parasitoïd |
Finally, monitoring the impact of the biological agent on the target pest and native fauna are essential components of this biological control program. Collected data allowed accurate assessment of the efficiency of G. ashmeadi attacking GWSS (e.g., parasitism rates, dispersion, and impact on pest density). The knowledge of potential impacts of the biological control agent on non target species permits an evaluation of the possible ecological costs of the control program and whether the environmental risk associated with releasing the natural enemy are merited. |