Environmental DNA is an efficient tool for monitoring pesticide resistance mutations in pest insects

BACKGROUND Environmental DNA (eDNA) metabarcoding is a revolutionary tool for monitoring biodiversity. In addition, eDNA can also detect the presence and frequency of nuclear genomic mutations in single‐species assays. In agricultural systems, this could provide a powerful tool for detecting and estimating the relative frequency of pesticide resistance mutations in pest arthropods, enabling more targeted resistance management. RESULTS We tested the possibility of using eDNA to detect the presence and frequency of mutations in the voltage‐gated sodium channel (VGSC) conferring pyrethroid resistance in the cabbage‐stem flea beetle (CSFB; Psylliodes chrysocephala ). We first tested the efficiency of eDNA for detecting mutations with a laboratory experiment, in which beetles with known resistance mutations were allowed to interact with cabbage ( Brassica rapa ) leaves. We then tested our approach with two field experiments. First, rapeseed ( Brassica napus ) leaves and individual beetles were collected to compare the relative frequencies of SNPs obtained from eDNA and conventional specimen‐based genotyping. Second, we used previously collected rapeseed stem‐bulk samples from various fields to explore the prevalence of resistance mutations. We show that plant‐derived eDNA can provide insights into the presence and frequency of resistance mutations, which are comparable to single beetle genotyping. CONCLUSIONS This study shows how eDNA is an efficient and scalable tool for pesticide resistance monitoring in agriculture, laying the foundations for future studies on resistance detection with eDNA and paving the way for precision agriculture.