The Asian stink bug, also known as the Chinese stink bug or brown marmorated stink bug, belongs to the species Halyomorpha halys and is the most harmful parasite to vegetables and fruit trees. It has only been present in our territory for a few years, but it is already seriously endangering fruit and vegetable production. The concern of both enthusiasts and professionals is due to the fact that this species of stink bug is not native to our ecosystem; in fact, it is also known as the Chinese stink bug.
It is crucial to learn how to recognize the different developmental stages of this parasite in case it is present in our field. This way, it becomes possible to understand how to prevent invasions in advance.
As a result, we can protect our crops using products allowed in organic farming, without the use of dangerous chemical pesticides.
In this article, we will see how to recognize the Asian stink bug, how to eliminate it, and the damage it causes to crops. We will also explore its biological cycle and the defense of vegetables and fruit trees.
What insect is the Asian stink bug
Halyomorpha halys is the scientific name of the feared Asian stink bug. It is an insect belonging to the order of Heteroptera, suborder Heteroptera, family Pentatomidae. It is a close relative of the more well-known green stink bug, which we have already talked about.
Spread of the Asian stink bug
As the common name suggests, this is a species of Asian origin stink bug.
It arrived in the United States in the 1990s and appeared in Europe towards the end of the 2000s. In Italy, it was first found in Modena in 2012. However, the fall of 2016 marked a turning point. A true invasion of Asian stink bugs hit the entire northern Italy. Since then, the Chinese stink bug has continued to spread throughout the country.
Appearance of Asian stink bugs. How to recognize them
Knowing the appearance of Asian stink bugs is crucial for identifying them in the field:
- These bugs are insects with a typical pentagonal shape.
- As adults, they can measure between 12 and 17 millimeters in length.
- The color of their upper parts is marbled, a perfect color for blending in with crevices and vegetation.
- A distinctive feature to recognize the adult Asian stink bug is the brown triangular marking on the rear end of their body.
- Another characteristic feature is their long legs.
These insects are skilled fliers and can travel long distances in search of vegetables and fruits to feed on and mate.
Chinese Stink Bug: Eggs, Nymphs, Nymphs, Adult
The activity of oviposition is very intense; each female can lay about 20-30 eggs.
They are laid in groups on the lower side of plant leaves, are whitish in color, and hard to spot.
The nymphs that emerge from the eggs are round and small, moving in groups and are orange in color, with horizontal black stripes. Between adults and nymphs, there are three intermediate stages of development (nymphs), during which the Asian stink bug becomes larger and less gregarious. The color changes from orange-yellow to the typical marbled pattern.
In the three photos below, we see the nymphs, the nymph, and the Halyomorpha halys adult.
How Long Do Asian Stink Bugs Live?
The lifespan of Asian stink bugs varies depending on the location. On average, in our country, this insect can complete two generations a year: an early one and another that finishes in late autumn. In countries with a milder climate, there’s only one generation. In their native areas, even three to four generations occur.
Asian Stink Bugs Indoors
The Chinese stink bugs overwinter as adult insects at the end of autumn. They seek shelter in vegetation for overwintering but can also try to enter homes. This poses a serious risk of infestation in homes near fields. In recent years, images of thousands of Asian stink bugs swarming windows have become common.
Mating, Egg Deposition, and Transition to Adulthood
Between April and May, the Halyomorpha halys emerges from shelters and moves to vegetation to mate.
Egg deposition occurs in June and July. Maturation to the adult stage takes place between late August and September. This is the period when the Asian stink bug’s presence becomes more pronounced.
What Does the Asian Stink Bug Eat?
The Asian stink bug feeds on various plants, making it a highly polyphagous species. It attacks numerous species of plants. The alert and interest in the Asian stink bug grew after the damage recorded in U.S. crops. While in its native Asian countries, the marmorated stink bug is considered an occasional pest of soybeans and some fruit trees, in the USA, it has affected over 300 species of fruit trees, vegetables, and ornamentals!
In Italy, attacks have already been recorded on trees such as: apricot, cherry, fig, kiwi, persimmon, apple, pear, peach, pomegranate, hazelnut, plum, walnut, grapevine, and olive. Among vegetables, the greatest damage occurs to: tomatoes, peppers, and beans. In short, a real scourge.
Damages Caused by the Asian Stink Bug
The damage caused by the Asian stink bugs to fruits and vegetables is due to their trophic activity, that is, their feeding punctures. This is a very troublesome damage that can be inflicted on many plants and quite rapidly. The reasons that make this pest more dangerous and devastating than many others are primarily related to some of its inherent characteristics:
- Attacks on crops are possible in all stages of the insect’s development;
- The high mobility of the stink bugs;
- The frantic search for shelter, which leads them to cause damage even after harvest.
To feed, these bugs use their piercing-sucking mouthparts. With their punctures, they suck out plant sap. The saliva they release triggers biochemical reactions that lead to necrosis of the affected plant tissues. Severe deformations can be observed in fruits, along with hardening in the exact area of the puncture. Indirect damage is caused by the excretions, which soil the fruits and give rise to annoying sooty mold.
How to Eliminate Asian Stink Bugs from Plants
Eliminating the Asian stink bug is a genuinely problematic task for all the reasons we’ve just explained.
Agricultural manuals often suggest chemical control as the main method for eliminating the brown marmorated stink bug. However, this strategy has proven to be ineffective from the outset. On the other hand, at Coltivazione Biologica, we keep repeating: chemical control brings more harm than benefits. Just think about the Colorado potato beetle, an insect that became more aggressive and resistant due to chemical treatments. Some species have significant adaptation and absorption capabilities for the various treatments they are subjected to in their DNA. This creates a vicious cycle: farmers apply increasingly strong, numerous, and toxic treatments to the environment, while the insects become stronger. Therefore, the only way is to intervene with biological remedies.
Marseille Soap and Soft Potassium Soap
To eliminate the Asian stink bug with biological control, it’s necessary to understand its vital mechanisms well. This insect breathes through the pores it has under its strong outer shell. So, it’s enough to block those pores to kill it. And Marseille soap, with its drying properties, is capable of sealing them. It should be noted that not all soaps are suitable. The practical solutions are:
- Soft potassium soap specifically for agriculture,
- Pure Marseille soap.
Both are products permitted in organic agriculture.
Pros and Cons of this Biological Remedy
The effectiveness of Marseille soap against Asian stink bugs depends on the difficulty of application. These Chinese stink bugs, in fact, have the habit of hiding under leaves, which makes the operation problematic. So, it becomes essential to thoroughly inspect the underside, which should be well-soaked. Another problem is dictated by the insect’s anatomy itself. If there is no direct contact with the pores, the solution cannot take effect. This type of intervention, therefore, has a higher chance of success when the Halyomorpha halys are in the nymph stage. When they are adults, their shell prevents the soap from penetrating the pores and makes the treatment less effective. Nymphs, on the other hand, move in groups, making them easier to reach. Here you can find an excellent soft potassium soap specifically for agriculture.
Insects that Eat Asian Stink Bugs
The emergency caused by the invasion of Asian stink bugs has put regional phytosanitary services and research institutes on high alert to find a solution. Unfortunately, in recent years, the economic damage caused by this oriental insect has been substantial. In some areas, the fruit and vegetable sector has been severely affected. The solution lies in finding insects in nature that feed on the Asian stink bug, the so-called antagonists; thus, it can be contained in an eco-friendly way. The endeavor is not easy, precisely because it’s an “alien” insect that lacks sufficient natural enemies in our environment. A first attempt was made by researchers at Crea with the insect Ooencyrtus telenomicida. This is a hymenopteran capable of parasitizing the eggs of Halyomorpha halys. Unfortunately, after the initial encouraging results, this research stalled. Thus, the controlled introduction of this antagonist insect was not possible. In 2019, another possibility was suggested by Crea, involving the use of the samurai wasp (Trissolcus japonicus). To date, we are still waiting for empirical data on experimentation and, above all, authorizations for the release of the antagonist insect in orchards.
How to Protect Fruit Trees from Asian Stink Bugs
As we have seen, the most significant damage from Asian stink bugs occurs on fruit trees. A successful agronomic defense technique tested by fruit growers is the use of insect-proof nets. The insect-proof net has proven to be an effective barrier for reducing the damage from feeding punctures by adults. Its application significantly limits the movement dynamics of populations, avoiding direct contact with plants. For very extensive orchards, this solution has a certain cost and is difficult to apply. However, on a domestic scale, to protect a few trees during the peak of infestation, it’s a simple and safe solution that we recommend adopting. This type of net also protects fruits from damage caused by severe hailstorms.
Here you can find suitable shade nets.
How to Get Rid of Asian Stink Bugs in Homes
After their summer and autumn banquets, Chinese stink bugs seek a cozy place to overwinter. Our homes, especially those made of wood, serve as excellent shelters. In late autumn or in the heart of winter, it’s essential to search around our garden to understand where Asian stink bugs might have nested. Decaying wood, large stones, cracks in concrete, and perforated bricks can be ideal hiding spots. That’s where we should start our search. Once the nest is located, it should be destroyed. Where allowed by amendments made to Legislative Decree 152 of April 3, 2006, fire is, in our opinion, the best solution. However, of course, great care must be taken!
It goes without saying that fire is excluded if the Halyomorpha halys nest is inside the house. In that case, they should be captured and removed, so muster your strength and courage. To catch the bugs, many recommend using old clothes or sheets, preferably flannel. These should be placed in strategic locations or in an old cellar. The insect is attracted to the fabric and will likely end up trapped. At that point, it will be easier to collect the cloth with the bugs inside and get rid of them.
Why the Invasion of Asian Stink Bugs Occurred
The invasion of Asian stink bugs is likely due to international trade, just like in the case of the tomato leafminer, the oriental fruit fly, or the Japanese beetle. In fact, invasions of non-native insect species in our ecosystem are becoming more frequent. At this point, perhaps we should all stop and ask ourselves: “Does it make sense to continue engaging in international trade of agricultural products that can be grown locally?”
This kind of trade risks damaging ecosystems and ruining the work of many people. Not only that, it also creates conditions of exploitation for farmers, who sell their products at very low prices, a necessary step to keep their sales competitive in distant countries. With this type of trade, the greatest profit always goes to the large distributors that manage it. As if that weren’t enough, this trade doesn’t benefit consumers either. While they might save a few cents on their groceries, they end up with poorly inspected products on their tables. We can be even more certain that local ecosystems do not benefit from it. As we’ve seen, they often end up invaded by destructive insects for which they are unprepared. The Asian stink bug is a glaring example.
What Can We Do
But how can we prevent new invasions of insects like Asian stink bugs? The truth is that it requires the commitment of each one of us. Given the perverse mechanism of the international distribution of the fruit and vegetable sector, what needs to be done is simple: consume healthily and consume locally!
Therefore, the invitation we want to extend is to primarily boycott products from international markets as consumers. When buying a South American tomato, for example, we’re not supporting a small producer from South America; we’re only helping a huge distribution chain exploit that farmer and disrupt not only the ecosystem but also fair economic dynamics.
An example that stands out is the deforestation of the Amazon rainforest, carried out to create vast areas of intensive agriculture that is not environmentally friendly.