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Five things that really stink about the Brown Marmorated Stink Bug

“Marmorated stink bugs stink—literally and metaphorically. They are invasive, are damaging crops, and are spreading at an alarming rate.”

Fig. 1. The brown marmorated stink bug (Halymomorpha halys)– an invasive, agricultural pest spreading at an alarming rate from its introduction in Pennsylvania in 1998. Source: Wikipedia commons.

We recently found a brown marmorated stink bug crawling around in our office area. I knew this wasn’t good, but I wasn’t exactly sure why. I’m an entomologist (I study insects) and I study invasion ecology (effects of non-native species) so I had to learn more! After asking my colleagues and doing a bit of digging on my own, here’s what I learned:

1. The brown marmorated stink bug is non-native. This invasive insect was first noticed in Pennsylvania in the mid-1990s, but now is wreaking havoc across the country. It is native to China, Japan, Korea, and Taiwan, but even in its native range, it is an occasional agricultural pest with outbreaks damaging crops, especially apples, pears, persimmons, and soybeans [1,2].

20170518Broadley_fig2

Fig. 2. (click to enlarge) Brown Marmorated Stink Bug Distribution Map. Interactive version here.

2. They damage many fruit crops leaving behind “cat facing” – a characteristic blemish to the flesh of the fruit. They have nearly 200 host plants, including many trees and plants found in yards and forests. They can damage corn, soybeans, other bean varieties, nut crops, tomatoes, and green peppers [3,4]. The produce is still edible, but sure doesn’t look appealing.

Fig. 3. The bug has a piercing and sucking mouthparts, which it uses to suck plant juices – this leaves behind damaged fruit flesh like that seen above. Photo credit: Chris Bergh, Virginia Tech.

3. There are other native stink bug species in the Northeast United States, but to distinguish this one, look for bands on the antennae and on the outer edge of their back. Also, check the underside of the insect in question – if it is brownish-gray rather than yellowish green then you have the invasive stink bug, not the more benign native bug [5]. Check out this site for photos of the look-alikes.

Fig. 4. Distinguishing features of the brown marmorated stink bug.

4. The brown marmorated stink bug is a pentatomid bug – a shield bug. Similar to many other species in this family, they literally stink. The term “stink bug” refers to the noxious smell they can emerge from scent glands on the their underside. The odor is pungent and some think it smells a bit like coriander.  It is thought that they emit it as a defense against predators.

5. What really stinks about the brown mamorated stink bug is their population densities. One resident in Maryland had over 26,000 stink bugs in his house over the course of a half year [6]. They typically have one generation, but if it’s warm, they can make it through 2 to 3 generations per year [3]. There are few natural predators of the brown marmorated stink bug in North America so little is suppressing their populations, allowing them to show up in droves.

Fig. 5. With no predators to keep them in check, marmorated stink bugs can show up in droves (Photo credit: Baldo Villegas).

Researchers are working hard to manage this insect. I was recently at the USDA Interagency Forum on Invasive Species and heard from a number of researchers working to control the damage and spread of this insect. Research is being conducted to see what pathogens or parasites kill them in China and to see if those same species could be effective for control here. There are a number of parasitic wasps that look promising, but more work needs to be done [7, 8].

Research into controlling stink bug numbers will take some time, so in the meantime, if you see them in your home, you can hand remove them or vacuum them up. It also helps to seal off cracks and crevices. I recommend being discriminate with pesticides, but a number of products have also been found to be effective in managing them.

References

[1] Jacobs, Steve, Sr. Extension Associate. “Insect Advice from Extension: Brown Marmorated Stink Bug.” PennState College of Agricultural Sciences, Department of Entomology. Feb. 2015. Accessed 16 Jan. 2017. http://ento.psu.edu/extension/factsheets/brown-marmorated-stink-bug

[2] Lee, DH, BD Short, SV Joseph, JC Bergh, and TC Leskey. 2013. Review of the biology, ecology and management of Halyomorpha halys (Hemiptera: Pentatomidae) in China, Japan, and the Republic of Korea. Population Ecology. 42(4): 627-641.

[3] Dara, Surendra. “Brown Marmorated Stink Bug in San Luis Obispo County.” Pest News: eJournal about endemic and invasive pests in California. 3 Nov. 2011. Accessed 16 Jan. 2017. http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=6120

[4] Stop BMSB: Host Plants of the Brown Marmorated Stink Bug in the U.S. Accessed 17 Jan. 2017. http://www.stopbmsb.org/where-is-bmsb/host-plants/

[5] Stop BMSB: Management of brown marmorated stink bug in US specialty crops. Accessed 16 Jan. 2017. http://www.stopbmsb.org/index.cfm

[6] Inkley, DB. 2012. Characteristics of home invasion by the brown marmorated stink bug (Hemiptera: Pentatomidae). Journal of Entomological Science. 47(2): 125-130.

[7] Warnert, Jeannette E. “‘Super pest’ takes hold in Sacramento neighborhood.” ANR New Releases: News releases form the UC Division of Agriculture and Natural Resources. 18 Sept. 2013. Accessed 16 Jan. 2017. http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=11487

[8] Talames, EJ, MV Herlihy, C. Dieckhoff, KA Hoelmer, M Buffington, MC Bon, DC Weber. 2015. Trissolcus japonicas (Ashmead) (Hymenoptera, Scelionidae) emerges in North America. Journal of Hymenoptera Research. 43: 119-128.

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