Brown marmorated stink bug
The brown marmorated stink bug (BMSB), Halyomorpha halys, is an invasive insect native to East Asia, which has spread and established in different areas of the world due to global trade.
Scientific name Halyomorpha halys
Distribution Not yet proven to have colonised the UK
Plants affected A wide range of ornamental, vegetable and fruit plants
Main symptoms Dark areas on leaves and fruits, fruit distortion
What is the brown marmorated stink bug?
The BMSB is a large shield bug, a similar size to several native species. It has generally brown and marbled coloration. The key features to distinguish the adult from other native shield bugs are its rectangular-shaped head and rows of pale dots across the body behind the head. It also produces a distinctive smell resembling coriander plants and, when it is present in high numbers, this may be considered unpleasant and disturbing. The juvenile stages (nymphs) are easier to recognise because, unlike any native shield bugs, they have spines on the sides of the body.
Adults have been intercepted in imported goods and luggage and a few individuals found free out of doors in England but so far other life stages (nymphs or eggs, confirming breeding) have not been found.
In 2022, a female, found in South East England, laid eggs after capture, though these were unviable. This suggests that the shieldbug may become established, especially with warmer summers which favour the insect.
The BMSB has a very wide host-plant range, feeding on more than 100 plant species, including important crops such as apples and brassicas alongside many ornamental and woody plants. It is a very mobile insect, which likes to move and feed on the sap of different plant parts including leaves, flowers, fruit and seedpods. Its feeding activity can be particularly troublesome, with low densities of the insect causing deformed flowers and fruit.
Additionally, during the winter months the insects find shelter indoors. The males produce an aggregation pheromone and in countries where the insect is established, a high number of adults can be found in buildings. This together with the unpleasant smell can make BMSB a public nuisance.
In order to understand better the presence and distribution of the BMSB in the UK, a national pheromone-based monitoring project is taking place, coordinated by NIAB EMR. This surveillance has led to the detection of a few individual BMSB adults in South East England.
If you believe that you have a found this bug, please take a picture and report the sighting at [email protected] or via email to [email protected]. In the meantime please keep the insect alive in a sealed container, as a live specimen might be required for further examination.
Adults overwinter in natural shelters such as cracks in tree bark, or in buildings and become active during spring when they start feeding on woody plants. After their emergence, they mate and the female insects lay clusters of eggs on the underside of leaves. The nymphs (five different instars) feed on plant tissues such as leaves, fruits and seed pods. Adults may start appearing in late summer and autumn.
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