Biological control of Gonipterus platensis: current status and new possibilities

Doutoramento em Engenharia Florestal e dos Recursos Naturais - Instituto Superior de Agronomia

The Australian weevil Gonipterus platensis (Marelli) (Coleoptera: Curculionidae), commonly known as the Eucalyptus snout-beetle, is one of the main pests of eucalypts. Because this is a non-native species, classical biological control with natural enemies from its region of origin should be a viable control strategy. The introduction of the Australian parasitoid Anaphes nitens (Girault) (Hymenoptera: Mymaridae) has been the main method to control the pest worldwide. However, this natural enemy is not completely effective in reducing G. platensis populations and does not avoid the occurrence of damage in several regions. Therefore, it is important to identify effective control alternatives for these areas. In this work, the economic impact of the pest and the benefit of biological control with A. nitens over the last 20 years were assessed, using Portugal as a case study. The results of the economic analysis showed that, without biological control, the losses caused by G. platensis would be at least four times higher than those occurring with partial control by A. nitens. Given the insufficient efficacy of A. nitens, the existence of other natural enemies in Australia that could be used in a classical biological control programme was evaluated. From a set of eight natural enemies identified in Tasmania, the egg parasitoid Anaphes inexpectatus Huber and Prinsloo (Hymenoptera: Mymaridae) was selected for further studies. Laboratory studies comparing the biology of A. inexpectatus and A. nitens at different temperatures, a competition study between these two species, and a risk analysis for the introduction of A. inexpectatus in the Iberian Peninsula were carried out. Overall results suggest that A. inexpectatus might complement parasitism by A. nitens under field conditions without non-target effects on native fauna

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