Evaluating biological control at the regional scale

Weeds that become targets for biocontrol projects often have a wide invaded distribution. The scale of the distribution offers a challenge to researchers for monitoring the outcomes of the project. A three-tiered structure for evaluation is described (using the Echium plantagineum project as a model), where Tier one provides robust relationships on plant and agent performance, Tier two provides key performance data derived from the relationships gathered in Tier one and allows for predictions on impact to be made, and Tier three provides easily collected data on agent establishment and dispersal. Tier one evaluation is the responsibility of the primary research group and is usually carried out at a limited number of sites. Tier two monitoring is carried out on a regional scale where sites are selected to represent the performance of agents in a particular climatic zone (or otherwise functionally discreet area); this work will usually involve officers from other collaborating organisations (such as state agricultural departments). The monitoring of establishment and dispersal, i.e. Tier three, should be carried out at all release sites, and usually involves input from the primary researchers, state departments, local government and community stakeholders. The information gathered at all levels should be captured centrally by the primary research group. This information will provide decision support for ongoing release programs (i.e. targeting an agent to suitable climatic regions and land management types), which will in turn maximise impact and provide an estimate of this impact over the entire distribution of the weed.