Validating the New Zealand Biocontrol Risk Model for Australia : Systematic surveys for non-target host use

Abstract

This research aims to determine whether weed biological control agents attack non-target plants that supported some development in host specificity testing. Field surveys were conducted for agents released to control six major Australian weeds: ragwort (Jacobaea vulgaris Gaertn.) English broom (Cytisus scoparius (L.) Link), gorse (Ulex europaeus L.), alligator weed (Alternanthera philoxeroides (Mart.) Griseb.), Montpellier broom (Genista monspessulana (L.) L.A.S.Johnson), and St John’s wort (Hypericum perforatum L.). A total of 10 agents, including mites and insects, previously released for biological control were examined, and host specificity checks were conducted. Overall, 15 potential alternative host plants were examined for agent attack as well as the target plants. All agents are well established in Australia and had been released from 12 to 44 years earlier. There was no evidence that the non-target species included in this survey were able to support full development of the agents, although an incidental finding of non-target host use requires further survey effort.