This three-year project was completed in mid-2022.
Environmental DNA (eDNA) detection methods are rapidly changing how we detect organisms in the field. Recent studies have shown that invasive pest insects including the Brown Marmorated Stinkbug (Halomorpha halys; BMSB) can be detected in the field using DNA collected from plant surfaces.
BMSB is an important biosecurity threat to New Zealand but current pheromone-based detection methods are suboptimal. Published eDNA detection methods for BMSB have been quite empirical, with relatively little known about the limits of detection and lifespan of insect DNA in the environment.
In this research we set out to quantify the period of exposure required before an insect is detected. We utilized the Green Vegetable Bug (Nezara viridula; GVB) as a surrogate for BMSB, and developed and tested several qPCR assays based on the GVB mitochondrial cytochrome oxidase gene. After allowing GVB to walk and feed on apples, we could detect the insects after 30 minutes exposure, with surprisingly little change in detection sensitivity up until 24 hours of exposure (between 0.01 ng to 0.001 ng of DNA/ul detected). A small improvement in detection sensitivity occurred from 32 hours to 72 hours (0.1 to 0.01 ng/ul DNA detected) Currently we are continuing with GVB exposures, from a broader range of substrates and across a much larger number of samples. This is important to develop a robust understanding of limits of detection. We are also investigating the degradation of insect DNA detection over time, and testing DNA metabarcoding vs qPCR as a method to detect a wider range of insects from environmental DNA.
The Zotero database is on the B3 homepage under ‘Outputs’.