The Brown Marmorated Stink Bug, Halyomorpha halys, has arrived in the UK, threatening fruit and vegetable crops during summer and heading inside people's homes during winter, according to a press release issued by the Natural History Museum on 1 March 2021. One of the first Stink Bugs to be identified was caught in the Museum's wildlife garden at South Kensington by Museum scientists. Native to China, Japan and Korea, brown marmorated stink bugs are fast breeding insects that come in various shades of brown and grow up to 1.7 centimetres long. The stink bugs get their name from the foul smell they exude when they feel threatened.
During the summer, these pesky pests feast on fruits and vegetables such as Apples, Pears, Peaches, Tomatoes and Sweetcorn by piercing the surface and sucking out the juice. They distort the produce and leave behind rotting spots and blemishes which can make the Plant inedible or unsellable. Max Barclay, the Senior Curator in Charge of Beetles at the Museum, says, 'If you eat a damaged fruit, there's no risk to your health. The fruit just doesn't look beautiful, so the sale value is reduced. These fruits usually end up as juice.' Sometimes Stink Bugs can end up in products made from fruits, such as wine, and contaminate the flavour. This often results in the entire crop being thrown away, a huge waste and loss of profit. Barclay says, 'If you have a bunch of Grapes that contain Stink Bugs and you grind them up into wine, you get the smell of Stink Bugs in the drink and people don't like that. You have the same problem with some Ladybirds which get into wine and spoil the taste of it.'
Ancestrally, Brown Marmorated Stink Bugs would hibernate in abandoned caves throughout winter. In inhabited areas, they are drawn to people's homes for warmth and shelter. These Stink Bugs were accidently introduced to the US in the mid-nineties and since then, have spread to 44 states. In North America, the Stink Bug population has grown exponentially and there are records of thousands gathering in houses. 'One of the reasons Stink Bugs are considered pests is because they cluster around window frames in large numbers and leave droppings,' says Barclay. 'If you try and sweep them away, they will produce these unpleasant smelling oils which will stain the furniture. If the oils get on your fingers, it's really hard to remove.' After visiting the US in 2014 and noticing a lot of Brown Marmorated Stink Bugs, Barclay predicted these pests would eventually arrive in the UK too, especially as they had already formed populations in some parts of Europe such as Switzerland, France and Italy. During that year, two Brown Marmorated Stink Bugs were found on imported timber at British borders. 'Once these things make a foothold, they establish pretty quickly,' says Barclay. 'We've seen this with a lot of invasive species before, like the Harlequin Ladybird. You find one or two, then five or six and then they're everywhere.'
Brown Marmorated Stink Bugs are considered an invasive species. The horticultural research organisation National Institute of Agricultural Botany's East Malling Research Station in Kent, has co-ordinated a trapping programme, funded by the Department for Environment, Food and Rural Affairs, to monitor the arrival of Brown Marmorated Stink Bugs. It involves lacing a small piece of double-sided sticky plastic with synthetically produced sex pheromone to attract the pest.
The Museum hosted a trap in its wildlife garden and last summer, caught a male stink bug. Another male was found on a pheromone trap in RSPB Rainham Marshes in Essex. These were the first two samples collected in 2020. At the end of that year, a resident in Surrey found one hibernating in her house.
'The trapping programme is more useful as a monitoring device than a controlling one,' explains Max Barclay. 'It's very difficult to control Brown Marmorated Stink Bug populations by killing individuals. Trapping is a good way of detecting the presence of the species which might influence your other behaviour, like Bug proofing your house or growing a different crop that is less susceptible to this pest.'
A team of UK-based researchers, including Max Barclay, Glen Powell at the National Institute of Agricultural Botany's East Malling Research Station and Andrew Evans from Scotland's Rural College have now published a scientific paper on the Stink Bug in British Journal of Entomology and Natural History. The researchers looked at how global warming will change the likely spread and establishment of Brown Marmorated Stink Bug within Britain and predicted the Bugs will inhabit London, as well as some parts of eastern England where it is the warmest.
Researchers at the National Institute of Agricultural Botany's East Malling Research Station are worried about the threat Brown Marmorated Stink Bugs pose to British crops. The species has a wide diet of over a hundred agricultural and ornamental flora species and could damage a large number of Plants in gardens and farms in the UK. Experts are currently researching how to manage this issue to avoid millions of pounds of economic damage.
The last invasive Insect species to hit the headlines in the UK was the Harlequin Ladybird, Harmonia axyridis. Native to Asia, this Ladybird was noticed by the public in 2004, eliciting both curiosity and caution. Soon, they multiplied to all over the country and they are now the most common Ladybird species in the UK. Invasive species like the Harlequin Ladybird and Brown Marmorated Stink Bug are able to enter the UK through increasing global trade and thrive due to climate change. Stink Bugs often hide in shipping crates and wooden pallets during winter - items which are moved around a lot. When spring arrives, the insects could be in a different country thus providing an opportunity to expand into a new part of the world.
At this stage, there isn't any evidence that shows the Brown Marmorated Stink Bugs have started to breed and establish populations in the UK so monitoring via pheromone traps is really important. If further bugs are detected, the National Institute of Agricultural Botany aim sto follow this up with field sampling around sites of capture. Detection and monitoring of early populations allows the National Institute of Agricultural Botany to alert growers of vulnerable crops who can then put crop protection strategies into place.
Fortunately, the UK can benefit from existing research that has taken place elsewhere in the world such as the US, which will help in developing effective control strategies. One idea is to attract large number of Stink Bugs into a net trap using pheromone and then treat them with a Plant protection product.
If members of the public think they have found a Brown Marmorated Stink Bug, the National Institute of Agricultural Botany encourages them to first check online to make sure it hasn't been confused with a native species such the Green Shield Bug which turns brown over winter. 'There's also a Sloe Bug named after the fruit they use to make Sloe gin,' adds Max Barclay. 'It's purplish brown and quite hairy under the microscope which the Brown Marmorated Stink Bug is not. But to the inexperienced eye, it would look very similar.'
If it turns out to be a brown marmorated stink bug, the scientists request that it is captured in a small container and posted to the Museum or National Institute of Agricultural Botany's East Malling Research Station. Images of stink bug suspects can also be emailed to Max Barclay or National Institute of Agricultural Botany's East Malling Research Station or for confirmation.
Max Barclay says, 'The Insect fauna changes all the time. We have about 27 000 species of Insects in the UK and about 5% of them have arrived here in the last few decades. It's only occasionally we get an invasive species that draws attention to itself by being a nuisance species or reaching very large populations. The last one was the Harlequin Ladybird, which was about 15 years ago. Now it's the Stink Bug.'
Further information regarding the brown marmorated stink bug and its likely spread and impact within the UK is available via a recent webinar produced by the Agriculture and Horticulture Development Board.
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