New test to bolster defences against catastrophic ‘hitchhiker’
Pest and Disease ManagementResearchers have developed a diagnostic tool to add to surveillance powers and help prevent an incursion of brown marmorated stink bug.
Key points
- An environmental DNA (eDNA) test has been developed to assist with the rapid detection of brown marmorated stink bug (BMSB), a highly destructive exotic pest.
- BMSB is not present in Australia but interceptions of the bug at Australian ports have been growing for several years.
- A voracious feeder, the bug’s saliva causes significant damage to fruit and can result in sunken areas, corky spots and scarring.
Australian researchers have developed a new tool to bolster the lines of defence against an exotic pest that would devastate the apple and pear industry if it breached the national border.
Brown marmorated stink bug (BMSB: Halyomorpha halys) is native to China, Japan and Taiwan but has spread and established itself as a serious horticulture pest on other continents, including North America and Europe.
While it is not present in Australia, BMSB is often found at the border by quarantine service agencies. Interceptions of BMSB at Australian ports have been growing for several years, with the bug known to ‘hitchhike’ on plant material and by hiding and hibernating in cargo of all kinds including vehicles, machinery, electrical goods or shipping containers.
The increased risk of transmission has arisen from establishment of the bug in countries that actively trade with Australia, such as the United States and Italy.
In response, the Novel technologies to assist rapid and sensitive detection of brown marmorated stink bug (AS19000) project has developed an accurate, fast and cost-effective diagnostic tool to add to surveillance powers and help prevent an incursion.
EnviroDNA molecular geneticists, Dr Haylo Roberts (left) and Sarah Licul (right), using robots in the laboratory to undertake large-scale eDNA testing during the project.
Rapid eDNA test developed
From 2020 to 2023, researchers at Cesar Australia in partnership with sister company, EnviroDNA, and Plant and Food Research New Zealand, developed the use of environmental DNA (eDNA) technology to assist with the rapid and sensitive detection of BMSB.
eDNA technologies are innovative species detection tools, being used in Australia and overseas for a range of activities in the fields of biosecurity, biodiversity conservation and environmental impact assessments.
EnviroDNA molecular geneticist and field scientist, Dr Mackenzie Lovegrove, said a targeted eDNA test for BMSB has been developed and tested to ensure it is highly sensitive and specific, meaning it only detects BMSB and not other closely related insects.
“The eDNA technology will be available for use alongside existing surveillance mechanisms at the border to aid surveillance efforts, as well as incursion response activities should the bug be intercepted outside Australian ports,” Mackenzie said.
“All organisms leave traces of their DNA in their surrounding environment. The eDNA test now makes it possible to take environmental samples to determine what species are, or have recently been, present in near real-time.
“If the bug was intercepted outside Australian ports, the test will aid in an incursion response to help limit its spread. If someone sees something suspicious out in the field, this test can be used to determine if it’s BMSB.”
An eDNA sample being filtered by Dr Justine Larrouy who is a researcher with Plant and Food Research NZ
In-field testing
To assess how well eDNA sampling methods worked in the field, researchers developed a test for a surrogate species common in Australia and New Zealand, the green vegetable bug (GVB: Nezara viridula).
Simple methods for collecting GVB eDNA were developed and evaluated. The most practical and effective of these was sampling of leaves into a sealed bag, agitation in water, with eDNA then concentrated by filtration, extracted and tested. This method could be applied to plant surfaces more generally.
The effects of GVB density and the window of detection were investigated over a time frame ranging from one to 72 hours. The test was able to robustly detect a single GVB when present on a leaf for at least 16 hours in dry conditions.
“If BMSB were to breach our borders it would be catastrophic for many industries, including the apple and pear industry,” Mackenzie said. “Ensuring sampling methods are simple and effective, and that the test is as sensitive and robust as possible are key.”
In addition to developing the eDNA test, another key objective of the project is to improve awareness of BMSB and eDNA technology among biosecurity personnel and industry development officers.
The project team delivered a workshop with international eDNA experts at Plant and Food Research in Lincoln, New Zealand, in May this year, where the latest ideas and technologies were shared.
The team also developed a PestBites video (www.youtube.com/watch?v=-nQiJNdbhwI), which details the ways to survey and identify brown marmorated stink bug.
A review of the literature for the wine and horticulture industries on the impact and management of BMSB has also been undertaken.
The materials for a guide and workshop to train industry staff in the use of eDNA diagnostics are currently being produced.
BMSB nymph. Photo: Gary Bernon USDA APHIS, Bugwood.org
What is BMSB?
Brown marmorated stink bug (Halyomorpha halys) is a mottled brown-coloured, shield-shaped stink bug.
BMSB adults are medium to large (12–17mm long).
There are five nymph stages that range from less than 3mm to 12mm long. The nymphs are orange and black when they first hatch but quickly develop a similar colouration to the adults.
Eggs are cream to yellow-orange and approximately 1.6mm long, and laid in clusters on the underside of leaves.
Plant damage
It is a voracious feeder and is known to feed on more than 300 hosts, including significant horticultural crops, field crops such as soybeans and cotton and some grains, along with some ornamental plants.
Nymphs and adults use piercing-sucking mouthparts to feed. The insects feed on leaves, shoots and stems, and through the bark of some trees.
Both nymphs and adults prefer to feed on developing and ripe fruits and seeds.
While feeding, the bug’s saliva causes significant damage to plant tissues.
Feeding damage to fruit can result in sunken areas, corky spots and scarring. As the fruit develops, it may become discoloured and deformed. Premature fruit drop can also occur.
Feeding can also damage plant vegetative tissues, which can result in plant wilt and reduced vigour.
How does it spread?
It spreads as a hitchhiker on a range of commodities.
Once in a country, the adults are capable of flight, allowing localised spread of the pest.
Potential impacts of BMSB
Overseas experience has shown that if the bug established in Australia, it would have a significant impact on horticulture, grains and cotton crops, nursery stock and ornamental plants, along with potential damage to other plants in our environment.
The bug also causes significant issues for the general community as it can be found in the thousands seeking shelter in buildings and equipment and has a foul-smelling odour when crushed or disturbed.
The Centre for Agriculture and Biosciences International (CABI 2016) has found evidence that BMSB can cause:
- losses of up to 90 per cent for pome and stone fruit
- damage exceeding 50 per cent under heavy infestations of vegetable crops
- taint and contamination of harvested fruit, particularly for small fruit and grapes, making tainted wine a major concern for the viticulture industry
What should I look for?
Look for any unusual stink bugs on your plants or unusual aggregations of stink bugs in or on buildings. Report any unusual sightings to the Exotic Plant Pest Hotline on 1800 084 881.
Sources
www.planthealthaustralia.com.au/wp-content/uploads/2020/02/Brown-marmorated-stink-bug-FS-2.pdf
Further reading
“Rapid spread of BMSB calls for extra vigilance”, AFG Summer 2019, https://apal.org.au/bmsb-vigilance-global-spread/
Acknowledgement
The Novel technologies to assist rapid and sensitive detection of brown marmorated stink bug (AS19000) project includes funding from Australian agricultural industries through the Hort Innovation Hort Frontiers fund and Wine Australia, with in-kind and cash investments from project partners.
This article was first published in the Spring 2023 edition of AFG.
