Evaluating scent detection dogs as a tool to detect pathogenic Phytophthora species

Abstract

AbstractThe fungal genus Phytophthora includes an array of destructive plant pathogens that have had severe impacts on native, agricultural, and horticultural systems worldwide. Preventing the spread of Phytophthora species is critical for protecting vulnerable plants and ecosystems; yet detection remains a challenge due to their microscopic size, broad host range, and latent and cryptic expression in host plants. We tested the effectiveness of trained detection dogs to discriminate the odor of a target Phytophthora species, from among other non‐target odors, by conducting a multi‐choice experiment. We tasked two dogs with discriminating the scent of P. agathidicida—the causal agent of the lethal root rot disease “kauri dieback”—from two non‐target Phytophthora scents (P. cinnamomi and P. multivora), and four non‐target control treatments. We assessed the dogs' scent detection abilities by measuring the sensitivity and precision of their indications toward the target scent over 120 randomized trials. The dogs had a combined sensitivity of 68.6% (CI: 64.1–72.9) and precision of 52.2% (CI: 48.1–56.4), meaning they often identified P. agathidicida when it was present but also signaled on the other non‐target Phytophthora species. Moreover, we characterized the nature of false positive indications made for non‐target scents, which has important implications for how future multi‐choice experiments should be conducted. Our study shows that detection dogs are likely to be an adequate first‐pass detection tool for Phytophthora within a wider biosecurity framework. However, further research is warranted before dogs can be deployed for this purpose in the field.