Two-phase open-field test to confirm host range of a biocontrol agent cleopus japonicus

Abstract

The buddleia leaf weevil, Cleopus japonicus, was released in New Zealand in 2006 as a biological control agent for the weed Buddleja davidii. A two-phase open-field design was used to confirm laboratory host range and examine non-target impacts in the field. This was the first field trial undertaken in New Zealand and included six non-target plant species. Feeding and dispersal of the agent on the test species and B. davidii were compared. Cleopus japonicus strongly preferred B. davidii. Larvae were recorded on Verbascum virgatum and Scrophularia auriculata during the choice stage of the trial. Killing the B. davidii plants in the second phase resulted in adults feeding on the two exotic species, V. virgatum and S. auriculata. Minor exploratory feeding was recorded on the natives Hebe speciosa and Myoporum laetum. These results confirm that laboratory tests conducted to assess the safety of this agent for release in New Zealand accurately predicted field host range.