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Brown marmorated stink bug (BMSB), Halyomorpha halys, is an important exotic pest insect in Oregon. It first arrived from Asia to the Portland area around 2004. This insect is relatively unique as it affects a wide segment of Oregon society including citizens, business owners, and farmers. In and around the home BMSB is a problem when it aggregates on structures where it overwinters and can become a continual winter annoyance to residents. It also has a negative effect on urban agriculture including backyard gardens where it damages fruits and vegetables, sometimes causing complete crop destruction. Businesses are also targeted by BMSB for overwintering. In the urban environment populations of the pest build up primarily on ornamental trees. Farmers are most adversely affected by the pest. BMSB causes feeding damage on a huge spectrum of crops, including high-value specialty crops such as vegetables, hazelnuts, tree fruits, and small fruits. In other areas of the country management of BMSB in agriculture has been very challenging and costly. Current management programs are heavily reliant on insecticides and this has disrupted Integrated Pest Management (IPM) Programs that took years to develop.
Oregon offers BMSB a comfortable environment with abundant habitat and less pressure from natural enemies than it has in its native range of China, Korea, and Japan. However, that may be changing as its chief natural enemy in Asia was discovered in 2015 along the Oregon border in Vancouver and in 2016 in Portland. This natural enemy is a minute wasp (1-2 mm) called Trissolcus japonicus. Female wasps seek out the egg masses of BMSB and they lay their own eggs inside. Instead of the BMSB eggs hatching with BMSB nymphs, they instead produce a new set of wasps. They don’t sting people but a clear sign of their activity are BMSB egg masses that darken to a black color. BMSB is present in counties throughout Oregon, but are most prevalent in the Willamette Valley where BMSB can be locally abundant in urban, rural and natural areas. In eastern and southern Oregon, BMSB has been largely restricted to urban areas where the greatest concentration and diversity of deciduous trees are found.
Key characters for identifying adult BMSB and distinguishing them from similar species, are (1) the distinct light light bands on the dark antennae, (2) smooth "shoulders", and (3) abdominal margins have a distinct banding pattern.