A decision tree for evaluation of exotic plant pathogens for classical biological control of introduced invasive weeds

Plant pathogens for biological control of weeds must satisfy criteria for efficacy, safety, and deployment before they are actually included in the list of candidates for weed management strategies. Decisions are made throughout the development of each candidate agent concerning whether or not further research is justified. These decisions concern pathogen attributes such as collection information, Koch's postulates, long-term storage, host specificity, risk, and other factors, including deployment. In addition to the scrutiny from researchers, who become advocates at the time a proposal is made to regulators for introduction or utilization of a candidate, the proposed use of exotic pathogens for release receives additional review by regulators in the United States Department of Agriculture (USDA)-Animal and Plant Health Inspection Service (APHIS). In this paper, the processes for deciding whether to continue or abandon research on a candidate exotic pathogen for classical biological control of weeds in the United States are examined. Discussion is based on the experience accumulated at the Foreign DiseaseWeed Science Research Unit of the USDA-Agricultural Research Service but has broader application to programs involving evaluation of foreign candidates for biological control of any invasive species.