Using Environmental DNA as a Plant Health Surveillance Tool in Forests

Plant pests (including pathogens) threaten forests, reduce carbon sequestration, disrupt trade, and are costly to manage. Traditionally, forest surveys involve the visual inspection of trees for symptoms of disease; however, this process is time consuming and by the time symptoms are observed, the disease may be widespread. New methods of surveillance are needed to help plant health authorities monitor and protect forests from disease. Previous research has shown that metabarcoding of environmental DNA (eDNA) can be used to identify plant pests. This study collected rainwater samples from five forest sites across Northern Ireland every month for a year to examine whether eDNA metabarcoding could help authorities detect plant diseases in forests. Metabarcoding of the internal transcribed spacer (ITS) region was used to determine the fungal and oomycete profile of rainwater samples that passed through the canopy of spruce, pine, oak, and ash trees, along with a non-tree field trap. In total, 65 known plant fungal and oomycete pests were detected; seven were regulated pests, and two were pests that had not been previously identified in Northern Ireland. This work demonstrates that metabarcoding of eDNA from rainwater can detect plant pests and could be used in forest surveillance programmes.