What’s causing a stink? Identifying volatiles from stink bugs

Brown marmorated stink bugs are considered one of the top pests of concern for New Zealand’s horticultural industry. Armed with a characteristic shield-like shape, they are differentiated from other stink bugs present in New Zealand by a zebra-esque pattern on their abdomen and antennae. Roughly the same size as a $1 coin, these tiny invaders should not be underestimated.

These stink bugs are not fussy feeders, known to eat anything from stonefruits and grapes to butterfly bushes and roses. As well as bugging both horticulturalists and gardeners, the bugs will crawl into your home over winter periods, giving off a peculiar smell that will, without-a-doubt, make your home stand out from the others. Our trips to the supermarket would be a lot faster as well with less fruit and veg options available.

A brown marmorated stink bug (CC BY-NC 2.0). Some rights reserved by Pierre Bornand, https://www.flickr.com/photos/kahhihou/22626302023/

The Ministry for Primary Industries has identified loaded containers as the most likely way the bugs would enter New Zealand, as they need a sheltered space to survive winter. At Lincoln University’s Bio-Protection Research Centre, Laura Nixon, alongside supervisors Michael Rostas, Stephen Goldson and Eckehard Brockerhoff, looked into methods for detecting diapausing brown marmorated stink bugs hiding in shipping containers and published a paper on their findings.

Stink bugs produce and give off organic chemicals called volatiles; the most recognisable being aldehydes – the volatile group responsible for the odour for which the stink bugs are named after. Laura hoped to see if the volatiles could be detected on cargo ships regardless of whether the bugs were in dormancy or not.

The research involved many hours of collecting bugs, which had naturally entered dormancy, and setting them up in carefully regulated sampling boxes which mimicked cargo ship conditions. Some bugs became agitated enough that they broke dormancy, others were encouraged to become agitated andthis group was called ‘diapause-disrupted’.

Diapausing and diapause-disrupted bugs were kept as two separate groups; diapausing bugs were left to do their own thing and remain dormant. Alternatively, diapause-disrupted bugs were provided food, warmer temperatures, and longer periods of light to encourage post-diapause behaviours. With careful lab work, volatiles were sucked from the air directly above the two groups of bugs for analysis.

A) Regulated sampling box. B) Inside of the sampling box (CC BY 4.0). Torri Hancock http://researcharchive.lincoln.ac.nz/bitstream/handle/10182/9201/Nixon%2c%20Identification%20of%20volatiles%2c%202018.pdf?sequence=1&isAllowed=y

Laura found that volatiles from both groups of bugs were very similar, with tridecane, an odour given off as a defence mechanism being the most common. Unfortunately, this volatile is not specific to the marmorated stink bug. It shares a similar chemical structure to volatiles given off from treated wood, floral scents, and other insects, making it unreliable to use in border security – imagine an airport detector dog smelling a perfume in your bag and thinking its a bunch of illegally imported fruits or seeds. She also found that more diapausing bugs released their odour defence compared to diapause-disrupted bugs – which makes sense as diapause-disrupted bugs could simply move away from any threats.

Other volatiles which are already known to be specific to stink bugs were detected in both diapausing and diapause-disrupted groups. From a biosecurity point-of-view, the release of these volatiles from both groups of bugs indicates a potential for chemical detection on cargo ships. As tridecane is not unique to this specific bug, other volatiles should be scanned for to prevent a stink bug invasion.

Biosecurity measures are already in place to prevent an invasion, involving requirements for importers to meet as well as screening imports on the border. As a result of this research, it is hoped that a successful method for the detection of brown marmorated stink bugs is developed. This would be huge for New Zealand’s biosecurity as any brown marmorated stink bugs could be detected and exterminated, preventing the species from entering the country and establishing populations beyond the border.

Further research on how movement and temperature fluctuations on cargo ships affect volatile emissions have already begun. In the meantime, everyone should be on the lookout for these distinctive, damaging bugs. If you think you’ve found one, put it into a plastic bag (or an airtight glass jar if you’re more environmentally conscious) and call Biosecurity New Zealand straight away on 0800-80-99-66.

The author Alexia Marr is a postgraduate student enrolled in the Master of  Applied Science at Lincoln University. She wrote this article as part of his assessment for ECOL608 Research Methods in Ecology.

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