Investigation of host plant contact with Diaphorina citri by detecting D. citri-derived environmental DNA

Citrus greening (Huanglongbing) disease has serious impacts on citrus production. Field monitoring of the Asian citrus psyllid Diaphorina citri (Hemiptera: Psyllidae), a vector of citrus greening disease, is essential to prevent the invasion and spread of this disease. This study reports a new method for determining the presence of D. citri and traces of contact with host plants by collecting leaves of host plants from the survey area and detecting the environmental DNA (eDNA) derived from D. citri. The results show that with the applied method the presence of D. citri can be determined. As D. citri-derived eDNA is contained in DNA solutions of plants with a history of contact with D. citri, we succeeded in detecting not only genes conserved in D. citri mitochondria but also genes of D. citri symbiont organisms consisting of Wolbachia, Wolbachia phage, Candidatus Carsonella sp., and Candidatus Profftella sp. Diaphorina citri-derived eDNA could be detected in host plants even after only 10 min of contact with D. citri and could still be detected 6 months after contact. This technology has the potential to trace D. citri from their traces without individual detection and is expected to greatly contribute to the early detection and invasion warning of citrus greening disease in the future.