Methods to select areas to survey for biological control agents: An example based on growth in relation to temperature and distribution of the weed Conyza bonariensis

• We develop a novel approach for prioritising surveys for biological control agents.
• We modelled in CLIMEX the distribution of Conyza bonariensis, a S. American weed.
• Model parameters were developed for a hypothetical biological control agent.
• Areas in S. America were identified as suitable to survey for agents for Australia.

A novel approach for selecting areas to survey for biological control agents, incorporating climate and a hypothesised biological control agent, is demonstrated using the target weed Conyza bonariensis (Asteraceae). This weed has become important in Australian cropping regions due to its persistence and herbicide resistance, and it is also increasingly an environmental weed. Both are reasons for the investigation of biological control options. We developed a species niche model for C. bonariensis in CLIMEX based on parameters informed by plant growth and distribution of the species in the Americas. A hypothetical biological control agent (HBCA-cold) was proposed that has its ideal growth range 5 °C below that of the weed, so as to favour development of the agent over that of the weed in parts of Australia. The southern part of the weed’s native distribution in Argentina, Chile and the highlands of Ecuador and Columbia were identified as the most suitable areas for surveys that take into account both the climate suitable for the HBCA-cold and the target regions in Australia. This was compared to a model (HBCA-hot) that had an ideal growth range 5 °C above that of the weed, but which identified potential areas for surveys in South America that were not climatically aligned with the main regions of the weed’s economic impact in Australia. This species distribution modelling method allows for prioritisation of search areas for biological control agents in the case of widespread target species such as C. bonariensis.