Physical characteristics and identification
BMSB are marbled brown, shield-shaped stink bugs with adults ranging from 12-17 mm in length. They have a rectangular-shaped head with rounded shoulders. The outer edge of the abdomen contains distinctive white banding, and the underside is a pale tan or yellow. Antennae each contain a pair of closely spaced white bands (Plant Health Australia 2020). Juveniles or nymphs are approximately 2.4 mm on hatching and have bright orange and black colouration, which progressively changes towards the characteristic mottled brown as they reach maturity.
The adults and larvae can potentially be confused with several other brown-coloured stinkbugs that are present in Australia. To assist with identification, the Department of Agriculture, Water and the Environment has produced a field guide.
Adult BMSB emerge from overwintering sites in spring, before mating and laying clusters of eggs on the underside of leaves. There are four flightless nymph stages that feed on fruiting crops as they reach maturity. The adult BMSB then often seek out later-season crops as they ripen before seeking overwintering sites that typically include under tree bark and in humanmade structures. Cold winters will see large numbers congregating in warm, sheltered environments, making them an urban nuisance throughout the entire year (Cira 2016).
Climate plays a role in determining the length of the BMSB growing season. Mild winters and early spring onset lengthen the growing season and can increase the number of generations produced each year, increasing the potential agricultural impacts (Kirstner 2017).
BMSB often arrive as ‘hitchhikers’ in shipped goods arriving from countries with established populations. When seeking overwinter shelter, they can find their way into goods awaiting shipment. They have been detected in a large range of goods that include bricks, vehicles, aircraft, and personal luggage (Haye 2015, Horwood 2019).
Adult BMSB are strong fliers and can fly 5 km per day in the search of a preferred food source, with some individuals capable of even greater distances. Average flying distances can increase towards the end of the growing season as suitable food crops become increasingly scarce (Wiman 2015). Flying ability is affected by ambient temperatures, with individuals not flying when temperatures fall below 16°C (Plant Health Australia 2017).