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Bug of the Week is written by "The Bug Guy," Michael J. Raupp, Professor of Entomology at the University of Maryland.

The gathering storm: Brown Marmorated Stink Bug, Halyomorpha halys


Stink bugs check out a shutter as a potential winter refuge.


Brown marmorated stink bugs (BMSB) will soon make headlines as they seek winter refuge inside homes and businesses. A native of Asia, BMSB first appeared in the United States in the middle 1990’s near Allentown, PA and is now found in 40 states ranging from coast to coast, border to border, with the epicenter in the middle Atlantic region. How has this bug spread so rapidly? Due to its penchant to hide in sheltered locations to pass the winter, it often invades vehicles, including campers. One vacationer reported driving their camper hundreds of miles away from a home in Pennsylvania, and unwittingly releasing BMSB in a new location.

Bark feeding is a strange behavior brown marmorated stink bugs employ in autumn.

What problems has this stink bug caused? In 2009, we heard reports from growers who sustained significant losses to peaches, pears, and apples from BMSB. 2010 was even worse with regional losses to apples alone exceeding 37 million dollars. This development was particularly disagreeable from a pest management standpoint. Over the past four decades, fruit growers have made enormous progress reducing the amount of pesticides used in orchards by implementing an approach called integrated pest management (IPM). IPM relies on creating an orchard ecosystem that supports natural enemies to help control fruit pests. Pesticides are used only when needed and growers carefully select insecticides that are least disruptive to the ecosystem or damaging to beneficial insects. By virtue of BMSBs remarkable reproductive and destructive potential, growers have been forced to resort to multiple applications of potent, residual insecticides to deal with this threat, thereby reversing years of progress made during the heyday of IPM. 

Over the past few years damaging numbers of BMSB have been seen in soybean fields across the region. 2010 witnessed record numbers of these stink bugs in fields of sweet corn. Plunging their sturdy beaks through the corn husk, they remove the nutritious contents of developing kernels. In some cases, so many kernels are damaged that the ear of corn fails to fill out. Stink bugs are not just a problem for conventional vegetable growers. With fewer options for insecticidal control, organic vegetable growers in the region have been overwhelmed. Community gardeners and homeowners have also been vexed when hordes of stink bugs lined ripening tomatoes, poked holes in the skin, and then drained the juicy tissues below, leaving speckled, puckered, and pockmarked fruit. Similar injury has been reported on peppers and many other vegetables.

With its beak deeply inserted into a tomato, a BMSB nymph sucks out the juice.  

We have also learned in the last few years that brown marmorated stink bugs dine on more than 150 different varieties of trees and shrubs used in landscape plantings. In autumn, they move to the trunk and plunge their beaks through the tree bark to extract nutrients from underlying tissues. This insult creates weeping wounds and the sugary exudates attract a variety of disagreeable stinging insects, including paper wasps and yellow jackets.  The long term effects of this type injury are under investigation. 

Sweet sap exuding from stink bug wounds may attract stinging insects.

For many viewers of Bug of the Week, stink bugs in apple orchards or corn fields probably seem like a remote problem. However, the nuisance potential of BMSB is almost without equal. After the autumnal ravaging of crops and trees, these stink bugs seek shelter in homes. This pending assault is no trivial matter. In 2011, a homeowner in western Maryland captured more than 26,000 BMSBs from January through June as they moved about his home seeking egress from their overwintering refuge. That’s a lot of nuisance!

Why do stink bugs enter homes and man-made structures in the first place? Many folks incorrectly believe they enter to be warm for the winter. Bear in mind that millions of years ago when BMSB evolved, there were no mansions or man-made structures to invade. In chilly locations where winter halts the growth of deciduous trees and shrubs and withers herbaceous plants, food for the plant-eating stink bug all but disappears. Cold slows movement and brings development of stink bugs to a standstill. During this inimical season, BMSBs seek refuges to chill-out where they are protected from the harsh weather and dangerous predators. Until recently, these natural winter redoubts were thought to be rocky crags and piles of leaf litter. However, a new study revealed that the loose bark of large, freshly deceased but still standing trees may be a prime winter hideout for BMSB. For a BMSB leaving a senescing field of soybeans, the siding on a home might look like a fine place to spend the winter.

After feeding on my sunflowers, these stink bugs will storm my home.   

While populations of brown marmorated stink bugs were lower throughout our region in 2011 and 2012, 2013 has been a year of exploding numbers of BMSB at our research plots in central Maryland. Scientists in West Virginia and Virginia also recorded high numbers of stink bugs in orchards and other crops. When will the invasion begin? Each day this week, I noticed adult stink bugs massing on the sunny side of my house and peeking through the windows. No doubt, these rascals were casing the joint and over the next several weeks they will attempt to enter my home in search of a cool protected spot to spend the winter. For all my attempts to caulk, plug, and screen them out, a few will get past my Maginot Line and it will soon be time to break out the vacuum. Will the autumn of 2013 be a repeat of 2010? We’ll soon find out.

To learn how to keep BMSB out and what to do when they get in, please watch the following video.



Bug of the Week thanks Doo-Hyung Lee, Doug Inkley, Tracy Leskey, Galen Dively, and other members of the BMSB Working Group for providing information and inspiration for this episode. Interesting studies including those by H. Martinson, M. J. Raupp, and P. M. Shrewsbury, “ Invasive stink bug wounds trees, liberates sugars, and facilitates native Hymenoptera”, and D. B. Inkley, “Characteristics of home invasion by the brown marmorated stink bug (Hemiptera:  Pentatomidae)”, were also consulted.  Support for our research on BMSB comes from USDA-NIFA SCRI Award #2011-51181-30937.

To learn more about BMSB biology, distribution, and management, please visit the following web site: