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.