Written by: Tianna DuPont, WSU Extension Specialist. Reviewed by Dr. Betsy Beers, WSU Extension Entomologist.
Brown Marmorated stink bug is an invasive pest unintentionally brought over from Asia which poses a significant risk to tree fruit producers. With 3.1 billion dollars of tree fruit at risk in Washington it is important to understand this new pest and potential controls in the case that it becomes an agricultural problem in Washington state. The following is a summary of Brown Marmorated Stink Bug information and research updates presented at the 2016 Orchard Pest and Disease Management Conference.
Current Status in Washington State
First found in the Mid-Atlantic region BMSB is already a nuisance pest in homes in Washington State and is rapidly becoming an agricultural problem. In Washington it is considered established in 14 counties. Hot spots in eastern Washington are primarily in Walla Walla and Yakima areas but we had the first cluster of finds in Douglas County in the fall of 2015.[i] Take a look at the map of BSMB finds here.
Some 50 scientists from multiple disciplines across the country have been working on a host of issues related to BSMB. They are documenting incidence and which monitoring tools work.
Aggregation pheromones are available from several vendors. Simple beating trays are also a good standby. Testing in the Northeast where BSMB reached agricultural pest status in 2010 shows that three traps (Ag Bio Inc, (800) 268-2020; Sterling Inc, (509) 343-3625, Rescue and clear sticky traps) used with attractants and kill mechanisms provide reliable and comparable presence/ absence and incidence data.[ii] Testing in California with Dr Chuck Ingels looking at the AgBio Pyramid Trap, a home-made double cone trap and the Trécé Double Cone trap also showed similar counts between traps for nymphs and 14% higher capture of adults in the Ag Bio Pyramid trap.
Traps should be placed on orchard borders as well as the first row of orchards. To better understand BSMB pressure at least one trap placed in the middle of the orchard far away from perceived outside BSMB pressures is helpful. Dr. Greg Krawczyk, Penn State University says, “Now we have confidence that the traps are working which allows us to use IPM again and not spray when the Brown Marmorated are not present in the orchard.”
How can you help?
Washington State University is still collecting specimens. Dr Beers urges Northwest growers east of the Cascade Mountains to bring suspected brown marmorated stinkbugs into their local extension office or extension research center for identification. “We want to monitor where the brown marmorated stink bug is and how far they have spread,” she said.
IPM for BSMB
Currently BSMB has not reached agricultural pest status in most parts of Washington. If and when it does it is recommended to monitor for BSMB using traps described above. As adults are highly mobile presence of nymphs in your orchard is a better indicator that control is needed. As effective sprays are generally broadspectrum (neonicotinoids and pyrethroids) monitoring will allow you to maintain your orchard IPM as long as possible.
Landscape Ecology and Behavior
Brown Marmorated Stink Bug adults are highly mobile and do not reside on a single crop or host plant. In the East where the pest is more common they have found that numbers are often higher in the perimeter of orchards and the woodlots and unmanaged areas surrounding orchards and fields. Wild hosts seem to act as a reservoir. For example when researchers surveyed transects looking at the border, intermediate area and interior of 18 orchards in Virginia, Pennsylvania and Maryland, they found that the highest number of fruit with damage were in the border.[iii]
It is less certain how the Brown Marmorated Stink Bug will do in Washington. “We hope that it [BSMB] will not do well in the dry climate of the west,” Dr. Beers says. But because we alter the environment with irrigation and landscape plants it may do fine, she explains.
When are Pest Populations High?
Populations dynamics depend on the season with models developed based on degree day temperatures[iv]. On average the first smaller spike in the population is in mid-June or early-July with a larger spike in mid-September. However, depending on degree days this can be highly variable, for example, reaching sufficient degree days in mid-August, 2012 and September 2013.[v]
Survivorship over Winter
In 2014 and 2015 there were indications that cold winters in the Northeast reduced populations.[vi] Extreme winter temperatures have the potential to lower over wintering populations when insects have not adequately acclimatized. During the winter of 2014 there was an extreme weather event ‘the polar vortex’ of low pressure and cold winter air where researchers were able to study the effects of cold on overwintering in the field. They found that BSMB is chill intolerant where adults died at a significantly warmer temperature than they froze, and no individuals survived if frozen. In Minnesota and Virginia, -16°C for winter acclimatized adults was lethal. However, BMSB tend to find refuge in the winter in human structures, the bark of trees etc. Adults that find refuge from winter temperatures will not have the same mortality rates.
A New Egg Parasitoid – Biological Controls for Brown Marmorated Stink Bug
In its native Asia, Brown Marmorated Stink Bug is parasitized by a tiny wasp T. japonicus. The wasp lays its eggs in BMSB eggs where the wasp larvae grow and eventually emerge, killing the BSMB eggs. There are native wasps in the US who also parasitize BSMB but they generally only parasitize a small number of egg masses compared to the 50-80% reported for T. japonicus. Because it is such an excellent biological control researchers have been working on bringing it into the country and have been evaluating it in quarantine since 2007. Then in 2014 they found T japonicus in the wild in Maryland. This year WSU’s Josh Milnes and Dr. Betsy Beers confirmed T japonicus in Washington in the wild. Using PCR, USDA scientists confirmed that the wasp is from a different area in China then the group in quarantine. “Nature beat us again,” Milnes said. This means there are wild populations of this effective parasite which will hopefully build up over time if Brown Marmorated populations increase[vii].
Spray programs are going to be difficult because of the number needed and the disruption to IPM programs.
Based on testing in the Northeast, the list of effective insecticides options is limited and includes products with only a few distinctive modes of action: pyrethroids (IRAC Group 3A): Bifenture and Brigade, Danitol, and Warrior; neonicotinoids: Actara, Assail, Scorpion and Venon; one carbamate product (IRAC Group 1A), Lannate, and some products including combinations of two different insecticide chemistries such as in Endigo or Leverage. While trying to limit the impact of BMSB on fruit, please remember also about seasonal limits for the number of insecticide applications per season.
Brown Marmorated Stink Bug Resources
[i] Brown Marmorated Stink Bug in Washington: A Growing Problem. Dr. Betsy Beers. Washington State University. Orchard Pest and Disease Management Conference. Portland Oregon. January 2015.
[ii] Re-Development of Effective IPM Programs in Pennsylvania Orchards Despite Presence of Brown Marmorated Stink Bug. Dr. Greg Krawczyk. Penn State University. Orchard Pest and Disease Management Conference. Portland Oregon. January 2015.
[iii] A Potpourii of BSMB Data from Virginia. Chris Bergh. Virginia Tech. Orchard Pest and Disease Management Conference. Portland Oregon. January 2015.
[iv] Nielsen, A. L., G. C. Hamilton, and D. Matadha. 2008. Developmental rate estimation and life table analysis for Halyomorpha halys (Hemiptera: Pentatomidae). Environ. Entomol. 37: 348–355.
[v] Seasonality and Distribution Pattern of Brown Marmorated Stink Bug (Hemiptera: Pentatomidae) in Virginia Vineyards. Basnet, T. P. Kuhar, C. A. Laub, and D. G. Journal of Economic Entomology, 108(4):1902-1909.
[vi] Cira, T.M., Robert, C.V., Aigner, J., Kuhar, T., Mullins, D.E., Gabbert, S.E., Hutchison, D., 2016. Cold Tolerance of Halyomorpha halys (Hemiptera: Pentatomidae) Across Geographic and Temporal Scales. Environmental Entomology 0, 1-8.
[vii] Discovery of an Exotic Egg Parasitoid of the Brown Marmorated Stink Bug and Its Potential for Biocontrol in Washington State. Josh Milnes. Washington State University. Orchard Pest and Disease Management Conference. Portland Oregon. January 2015.
WSU Tree Fruit Extension Specialist
WSU Professor of Entomology