Small bug with big appetite – The brown marmorated stink bug
A small stink bug, photographed in 1998 resting on a bicycle tire in Zurich, would become a threat to crop security in southern and central Europe almost 20 years later.
Profile
- The brown marmorated stink bug is native to China, Japan, Korea and other Asian regions.
- It is 12–17 mm long and of a dark brownish color.
- In Central Europe it can be mistaken for other species like Rhaphigaster nebulosa, Troilus luridus or Dolycoris baccarum.
- Able to infest an astonishing variety of plants species, it is a feared and destructive agricultural pest.
Classification
- Kingdom
- Animalia
- Phylum
- Arthropoda
- Class
- Insecta
- Order
- Hemiptera
- Family
- Pentatomidae
- Genus
- Halyomorpha
- Species
- H. halys
Life cycle
Females lay batches of 20–30 eggs on the underside of the leaves. Within a week, eggs hatch, and the miniature versions of the adult bugs (the nymphs) start feeding on the spot. You will never find larvae of the marmorated stink bugs because they are hemimetabolous* insects; this means that they do not undergo any radical transformation from the hatchling to the adult, apart of course from size growth. It takes 1–2 months for the nymphs to become reproductively mature. It has been estimated that, during its lifetime (which will not span more than four months), each female can lay eggs approximately six times.
In a nutshell
The French use the word punaise (meaning bug) to characterize an evil person. Imagine the magnitude of badness you convey if you are called a punaise diabolique. This is the French common name of Halyomorpha halys (family Pentatomidae), the brown marmorated stink bug, which invaded European croplands starting from Switzerland in the early 21st century.
Stench is the least of the problems that the marmorated stink bug can cause. This little shield bug is a voracious sapsucker, capable of infesting at least 200 plant species, whether wild or cultivated. It, therefore, currently represents one of the most destructive agricultural pests in the world.
What happens in Zurich, stays in Zurich … not!
The China Garden Zurich (Chinagarten Zürich) is one of the most prestigious Chinese gardens outside China. It was a gift to the city of Zurich by the city of Kunming, after Switzerland had provided technical support for expanding drinking water supplies and drainage. Yet, in 1998, the renovation of the garden would initiate a nasty pest invasion, as the boxes shipped from China, containing the traditional bricks needed for restoring the pagodas, included an unwanted hitchhiker: Halyomorpha halys.
The brown marmorated stink bug is native to East Asia, including regions of China, Japan, and Korea. Therefore, due to the abundance of ornamental plant species of Asian origin, the bug felt at home in the China Garden and thrived. Unfortunately, apart from some occasional observations of single bugs in residential areas in Zurich, the first established population would not be discovered until nine years later, 8 km south of the China Garden, in a private property in Erlenbach, in the Canton of Zurich. Until 2013, the brown marmorated stink bug had already expanded in 11 cantons. In Europe today, H. halys occurs from Armenia to Spain, and from Finland to Southern Greece, representing one of the biggest emerging problems in agricultural areas and urban gardens.
Not being picky pays off
Brown marmorated stink bugs can suck the life out of almost all the major fruits cultivated in Europe, as well as several ornamental or wild plant species. Pears seem to be a favorite yum, but in Europe marmorated stink bugs are known to damage a wide range of fruits (like cherries, plums, apricots, apples, raspberries, and peaches), forest trees (like hazel and ash), and various vegetables (like tomatoes, eggplants, bell peppers, and broccoli). This very wide range of host plants, combined with the bug’s mobility, is a good reason why it is so hard to eradicate H. halys: even if you apply some control measure on a cultivation, the adult population of the bug can hop on another plant species nearby and survive the catastrophe.
What's the damage?
The saliva of the brown marmorated stink bug contains enzymes that liquify plant tissue. This leads to deformation or destruction of the leaves, fruit and seeds the insect pierces. While feeding, the stink bug may also transmit pathogens such as yeast to the plants.
In northern Italy, a financial loss of 356 million euros to peach, pear and nectarine harvests was attributed to the marmorated stink bug in 2019. In Switzerland, substantial damage to pears and peaches was reported in Ticino in 2015, and damage reports in 2018 and 2019 confirmed that the marmorated stink bug has become a threat for specialized crops in many regions of Switzerland.
What's the solution?
So, is the brown marmorated stink bug uncontrollable? Well, the rapid expansion throughout Europe and in the USA, suggests that obviously this pest is hard to control. And sadly, future predictions are not very optimistic, as they show that a warmer atmosphere, due to climate change, is going to make H. halys emerge from hibernation earlier and produce multiple generations per year. Currently, as no pesticide has yet been approved in Switzerland, the most effective approach is to prevent the bugs from accessing the crops, either by bagging the fruits in fine nets or by sealing even the smallest openings in the greenhouses.
Samurai to the rescue!
But the game is not lost. One solution is to let the samurai do the dirty job. We are not talking about real samurai; besides, the samurai caste in Japan was abolished in the 19th century. This is all about biological control, i.e., the utilization of the natural enemies of H. halys for controlling their populations and limiting the damage. The samurai wasp (Trissolcus japonicus) is an Asian parasitic wasp (also unintentionally introduced to Switzerland), the females of which are known to inject their eggs into the eggs of the stink bugs, which die off before baby wasps hatch. Research on parasitoids and other natural enemies (e.g., pathogens) of H. halys, is still ongoing but, luckily, the results are very promising.
Neighborhood watch
Can we do anything? YES! We can help monitor the populations of H. halys. We know for a fact that citizen science can help combat invasions by providing valuable information on the geographical distribution of pests. Specifically for the brown marmorated stink bug, everyone can record when and where they last saw H. halys, on the internet platform halyomorphahalys.com or in the smartphone apps iNaturalist and bugMap. Perhaps, if citizen science apps had been a possibility back in 2000, farmers in Europe today would sleep much better at night.
Smells like stress – fun fact
Like stink badgers, stink bugs release unpleasant odors when they feel threatened; in the case of H. halys, its aroma contains specific aldehydes that may make it reminiscent of coriander.
Citizen Science
According to the Swiss Citizen Science Principles working group, citizen science is "a scientific method that enables citizen scientists and full-time researchers to work together and gain knowledge". The term citizen scientists refers to people who are not employed by a research institution and who voluntarily participate in a research project. An overview of citizen science projects in Switzerland and further information can be found on the website Schweiz forscht (in German and French).
*Glossary
Hemimetabolous insects do not undergo a metamorphosis as we know it from butterflies. They go through several molts and gradually develop into adults. The juvenile stages look like miniatures of the adult animal and are called nymphs.
References
Oppliger M. 2018. Er mieft, frisst unser Obst und es gibt immer mehr davon: Der Stinkkäfer erobert Europa. Tageswoche. https://tageswoche.ch/wirtschaft/er-stinkt-frisst-unser-obst-und-es-gibt-immer-mehr-von-ihm-der-stinkkaefer-erobert-europa/ Accessed 19.3.24
Haye T et al. 2015. Range expansion of the invasive brown marmorated stinkbug, Halyomorpha halys: an increasing threat to field, fruit and vegetable crops worldwide. J Pest Sci 88:665–673. https://doi.org/10.1007/s10340-015-0670-2
Wermelinger B et al. 2008. First records of an invasive bug in Europe: Halyomorpha halys Stål (Heteroptera: Pentatomidae), a new pest on woody ornamentals and fruit trees? Mitteilungen der Schweizerischen Entomologischen Gesellschaft 81:1-8. https://doi.org/10.5169/seals-402954
Cianferoni F et al. 2018. Review of the occurrence of Halyomorpha halys (Hemiptera: Heteroptera: Pentatomidae) in Italy, with an update of its European and World distribution. Biologia 73:599–607. https://doi.org/10.2478/s11756-018-0067-9
National Centre for Climate Services (NCCS) 2023. Invasive Insect Pests: The Brown Marmorated Stink Bug https://www.nccs.admin.ch/nccs/en/home/sectors/agriculture/impacts-pests/halyomorpha.html Accessed 19.3.24
Agroscope. Überwachung und Bekämpfung https://www.agroscope.admin.ch/agroscope/de/home/themen/pflanzenbau/pflanzenschutz/neobiota/halyomorpha/halyomorpha-ueberwachung-bekaempfung.html Accessed 19.3.24
Falagiarda M et al. 2023. Factors influencing short-term parasitoid establishment and efficacy for the biological control of Halyomorpha halys with the samurai wasp Trissolcus japonicus. Pest Management Science 79(7):2397-2414. https://doi.org/10.1002/ps.7423
Iacovone A et al. 2022. Augmentative biological control of Halyomorpha halys using the native European parasitoid Anastatus bifasciatus: Efficacy and ecological impact. Biological Control 172:104973. https://doi.org/10.1016/j.biocontrol.2022.104973