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Stink bugs are truly bugs and truly stinky

By Claire LaCanne

There are several misnomers for various insects out there. Fireflies or lightning bugs are neither flies nor bugs. They’re beetles. Lady bug? Also a beetle. Velvet ants are velvety, but they’re wasps, not ants. Hornets are wasps but not all wasps are hornets. The common names for insects can be confusing, but in the case of the stink bug, both parts of its name are accurate.

Stink bugs are considered true bugs, in the insect order Hemiptera. True bugs, which have piercing-sucking mouthparts, are effective pests and predators, depending on the species. There are herbivorous stink bugs and predatory stink bugs, and some species are considered pests of agricultural and garden crops.

A new threat to our crops and gardens in Minnesota is Halyomorpha halys, the Brown Marmorated Stink Bug (BMSB). The BMSB will feed on over 300 different plants species including many different fruits, vegetables, and row crops. The injury from their piercing-sucking mouthparts can lead to significant plant damage.

As for the stinky part, stink bugs can have a nasty odor. The scent of BMSB is usually described as earthy, and some people think it smells like cilantro. The odor comes from a defensive liquid the stink bugs secrete from a gland on the underside of their thorax when they feel threatened.

BMSB is not native; it was unintentionally introduced to the United States from Asia in the mid 1990’s and has been detected in Minnesota as a household invader since 2010. BMSB hasn’t been a significant agricultural pest in Minnesota, but it has been an agriculturally relevant issue in eastern states. However, BMSB was recently detected in Minnesota soybean; a single adult specimen was collected from a soybean field in Dakota County in August 2016.

Research at the University has confirmed that maturity groups of soybeans grown in Minnesota are susceptible to injury by BMSB, which can result in reductions in yield and seed quality. To stay ahead of this potential issue, scouting for BMSB should be performed with a sweep net during pod and seed development. Scouting should include locations on field edges and the interior of the field, because stink bugs are often more abundant on field edges. Thresholds for treatment are 10 bugs per 25 sweeps for soybean grown for grain and 5 bugs per 25 sweeps for soybean grown for seed.

Keep an eye out for the buggers; the BMSB is about half an inch long and its appearance differs from most native stink bugs. The three features that distinguish it from other stink bugs are white stripes on its antennae, rounded shoulders instead of pointy shoulders, and alternating dark and light banding around the abdomen.

Unfortunately, because BMSB overwinters indoors, our crazy weather this winter will not affect their populations this 2018 growing season. As populations of this stinky bugger increase in Minnesota, they may become more frequently encountered in crops and gardens. At the very least, you can curse this critter’s name knowing that it is systematically correct.

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