Invasive brown marmorated stink bugs found in UK for first time, threatening crops

It may look like just another shield bug, but the brown marmorated stink bug, which has been trapped for the first time in the UK, could spell disaster for the country’s apple, pear and soft fruit producers.

As its name suggests, this shield bug is brown, marmorated (veined like marble), and stinks.

The species releases a powerful odour as a defence mechanism to stop it being eaten by birds or lizards, but human efforts to remove them or handle them can also release the smell.

While this may be unpleasant, the real concern is over the species’ appetite for fruit, which could have a considerable impact in the UK if it becomes widely established – as is now forecast.

The stink bugs are a well-known pest in south east Asia, where they originate, and also in the US where they became established at the beginning of the century.

They are spreading around the world and in recent years have become increasingly common in European countries.

The arrival in the UK has been detected through the use of pheromone lures. Previously spotted in London and Hampshire, the bug has now been caught at a pheromone trap at the RSPB’s Rainham Marshes nature reserve in Essex.

A network of 19 traps across the south of the country to monitor insects is being managed by scientists at NIAB EMR – the horticultural research institute based at East Malling in Kent.

Dr Glen Powell, an entomologist at NIAB EMR, said: “This discovery of this flying adult of the species shows that the pest is present in the UK, and supports our concerns that the bugs may be actively dispersing in search of mates and food plants this summer and in the future.”

The scientists are now searching for signs of a colony to see if the species has been breeding ahead of over-wintering.

If such evidence is discovered there is the concern the bug could emerge in greater numbers next year, increasing its potential to damage UK crops.

This research, funded by Defra, could help avoid the stink bugs causing millions of pounds of economic damage.

After establishing themselves in the US in 1998, by 2010 the insects were estimated to have caused $37m (£26.5m) worth of apple losses due to feeding.

The bug has a very wide host-plant range, the scientists said and its arrival could spell problems for many plants found both in horticulture and domestic gardens.

The stink bugs inject their saliva into developing fruits and use a proboscis to feed. The saliva injection causes the fruit to distort in shape and become stained inside, making them unsalable.

The positive identification of the stink bug in Essex comes as the scientists at the NIAB EMR examine which pests are likely to arrive as a result of climate change or accidental import.

The traps were specifically designed to attract this bug.

The aim is that any invaders can be detected and monitored at an early stage, and fruit growers advised accordingly. This would be followed by research and development of robust, sustainable control strategies.

The scientists said the stink bugs “have a habit of hitchhiking with imported goods”.

It has been intercepted on several occasions at UK ports over the last 10 years, but has only been reported in the field more recently, with two over-wintering adults found at separate locations in Hampshire during 2018 and last year.

Dr Powell said: “This first record of an adult BMSB at a UK pheromone trap is very significant.

“We have currently been focusing some attention to detecting any possible populations in Hampshire, following earlier records but our traps in that county have not yet caught any individuals.

“The capture of this flying adult in Essex reveals that the invasive species is actively dispersing within the UK. The growth and development of these insects is likely to have benefitted from the recent warm weather, and we will continue to check our network of pheromone traps throughout the autumn.

“We follow up any positive identifications with field visits, actively searching for further signs of adults, or the immature stages and egg masses that would confirm that breeding is taking place.”

The scientists said the captured stink bug was spotted thanks to the vigilance of an RSPB volunteer and keen entomologist.

The adults of this new invasive pest are very similar in appearance to those of some of our native UK shield bug species, making it difficult to differentiate between them.

However, the brown marmorated stink bug has “a distinctly rectangular head and unique patterns of pale patches on the antennae and across the body”, NIAB EMR said.

The organisation said any grower or member of the public suspecting they have found a brown marmorated stink bug should email Dr Powell on bmsb@emr.ac.uk – attaching a photograph of the insect.