A molecular method for biomonitoring of an exotic plant-pest: Leafmining for environmental DNA

Abstract

1. Understanding how invasive species respond to novel environments is limited by a lack of sensitivity and throughput in conventional biomonitoring methods. Arthropods in particular are often difficult to monitor due to small size, rapid lifecycles, and/or visual similarities with co-occurring species. This is true for the agromyzid leafminer, Liriomyza sativae, a global pest of vegetable and nursery industries that has recently established in Australia. 2. A highly robust method based on environmental DNA (eDNA) was developed exploiting traces of DNA left inside 'empty' leaf mines, which are easier to collect and persist longer in the environment than the insect. This extended the window of possible diagnosis to at least 28 days since a leaf mine became empty. The test allowed for visually indistinguishable leafmining damage caused by L. sativae to be genetically differentiated from that of other flies. 3. Field application resulted in the identification of new local plant hosts for L. sativae, including widely distributed weeds and common garden crops, with important implications for the pest's ability to spread. Moreover, the test allowed for the confirmation of L. sativae on an island with a previously unconfirmed population. 4. The developed eDNA method is likely to become an important tool for L. sativae and other leafmining species of biosecurity significance, which, historically, have been difficult to detect, diagnose and monitor. More generally, eDNA is emerging as a highly sensitive and labour-efficient surveillance tool for difficult to survey species to improve outcomes for agricultural industries, global health, and the environment.

Sensitive environmental DNA (eDNA) methods to detect hemlock woolly adelgid and its biological control predators Leucotaraxis silver flies and a Laricobius beetle

“…Visual inspection methods can be limited spatially and temporally, while eDNA can persist over time and be transported easily through space. While studies exploring eDNA degradation rates on foliage are limited, agromyzid leafminer ( Liriomyza sativae Blanchard) eDNA was found 28 days after the leafmines became empty (Pirtle et al, 2021) and mammal eDNA has been reported to persist for up to 24 weeks on foliage after browsing (Nichols et al, 2012), but eDNA associated with A. tsugae wool may be protected for longer periods through shading or adsorption (Kessler et al, 2020; Kirtane et al, 2020; Valentin et al, 2021).…”