eDNA detection of invasive insects

This three-year project was completed in mid-2022.

Project Abstract

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.

Biosecurity outcome

• The suitability of eDNA for biosecurity surveillance will be assessed (proof-of-concept) using a pentatomid/brown marmorated stink bug model system. This will include the establishment of baseline information on eDNA detection of BMSB in NZ and comparison of eDNA detection with current technologies, with the ultimate aim of developing a BMSB eDNA trapping network.

Science outcome

• New approaches for eDNA preparation and amplification from terrestrial surfaces will be tested and reported.  “Simple” steps such as measuring and quantifying the detection limits for insect eDNA in the terrestrial environment will represent important scientific advances.
• The limits of detection for pentatomid/Brown Marmorated Stink Bug (BMSB) eDNA from environmental substrates will be quantified. Working with MPI, Port of Tauranga (PoT) and grower groups.

For information and publications on this and other B3 projects, visit Zotero.

The Zotero database is on the B3 homepage under ‘Outputs’.