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Sunday, October 10, 2010

A fall visitor: Brown marmorated stink bug

Stink bug adult on the hood of my car. Photo: HJB
After running errands Saturday morning, I noticed the insect above on the hood of my car. My apologies for the poor photo quality, but it was the best I could manage on the fly with my cell phone camera. This morning, another greeted me inside my living room window, leaving behind the trans-2-decenal and trans-2-octenal to prove it. From the glimpse I got, it appeared to be a brown marmorated stink bug (BMSB, Halyomorpha halys). This invasive insect has temporarily taken the place of bed bugs as the go to pest, garnering attention from the New York Times, Washington Post, and even NPR's Science Friday. A multi agency work group has been established to study BMSB biology, management, and regulation.

Why has BMSB generated so much interest this fall? For two main reasons:
1. Large populations have caused extensive damage in agricultural crops, and
2. They aggregate in structures in large numbers in the fall, becoming a nuisance pest.

First detected near Allentown, PA in 1998, BMSB has been present in the United States since then, but this summer their populations increased dramatically in the mid Atlantic. BMSB has been present in North Carolina since at least 2009, but has not reached the damaging levels observed in Maryland, north east Virginia, and Pennsylvania this year.

BMSB damage on an apple. The corky masses below the skin are distinctive of stink bug feeding. Photo: Penn State Extension
From mid summer through fall, BMSB has caused significant damage in the mid Atlantic to apples, peaches, caneberries, corn, and soybeans, to name a few of the crops it has been recorded from. Stink bugs, including our native species, the brown stink bug (Euschistus servus), green stink bug (Acrosternum hilare), and southern green stink bug (Nezara viridula), are difficult to manage with insecticides. Typically, broad spectrum materials, such as pyrethriods, carbamates, and organophosphates have been used to manage stink bugs, but may of these have the potential to create unintended consequences, like reducing natural enemies. Treatments for BMSB did not fit with carefully developed IPM programs for tree fruit in Maryland and Virginia, and resulted in greater pesticide use.

Stink bugs (native and non native) are emerging pests in many cropping systems due in part to their difficulty to control and in part to the increased number of insecticides (or other tools) that target a narrow range of organisms. For example, stink bugs are now a key pest of cotton due to the widespread adoption of Bt varieties that control caterpillars. Foliar applications of broad spectrum insecticides targeting caterpillars used to also control stink bugs but are no longer needed. The same scenario could apply to systems that have switched to other newer insecticides (i.e. Entrust, Delegate, Intrepid, Coragen, and many others) from broad spectrum materials.

The second reason BMSB has generated such wide attention is its tendency to aggregate in structures in the fall, much like the multicolored Asian lady beetle and another recently introduced bug, the "kudzu bug". All of these insects are native to roughly the same part of the world, China, Japan, and Korea, so it is possible that this fall aggregation behavior is associated with insects from these areas.

What should growers do if they suspect BMSB is present on their farm? Contact your cooperative extension agent to confirm identification and for management recomendations.

What should homeowners do if they suspect BMSB are present in their yards or homes? If BMSB are presents in your yard, there are few control measures that will be effective, and the most sustainable strategy is to tolerate injury to plants. If stink bugs are entering your home, seal entry points well (think of it as an entomological energy audit) and vacuum up the insects, disposing of your vacuum bag.

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