Whether they are brown or green, although totally harmless to humans and our pets, no one likes finding themselves in the house of bedbugs. In these autumn days you can see dozens and dozens of them on the walls and in the gardens Asian bedbugs brown (Halyomorpha halys), sort of invasive alien coming from Asian countries such as China, Japan and Taiwan, which seek shelter in sunny places protected from the cold. This year too there has been an explosion of this species in many Italian regions, particularly in the North-East. This is a phenomenon that is now showing signs periodic recrudescences: some years the presence is moderate and manageable, in others the specimens proliferate and become a real one scourge for many crops, especially fruit trees. Both harmless for humans and dangerous for crops: it causes considerable damage toagriculture, leading to significant losses in the fruit and vegetable sector and, more recently, also in corn and soya production. They are morphologically very similar to common green bugs Nezara viridula and to the native species Palomena prasinadifferent from these both for the marbled grey-brown color and for the geographical origin very far from our territories. Furthermore, it causes much more damage than that of green bugs, because it is numerically much more abundant and it has few natural enemies in our latitudes. But be careful not to crush them! Whether bright green or marbled, all bedbugs, if disturbed, are capable of emitting a acrid and persistent stench produced by particular odorous glands.
Characteristics of green and brown bedbugs: similarities and differences in appearance
In Italy there are four species of marbled bugs including, for some years now, the Asian bug (Halyomorpha halys). There are also four species of green bugs, of which the most common are the Southern green bug (Nezara viridula) and the Common green bug (Palomena prasina). They all belong to the Pentatomids, a family of Heteroptera insects which has 4,000 species worldwide. They are called Pentatomides because the body, when observed from above, recalls the geometric shape of one pentagonal shield.
By carefully observing both the adult and juvenile stages (nymphs), some differences can be seen:
- The Asian bedbugs they have a dorsal color gray-brown marbled with the outer edge of the abdomen (called connexivum) characterized by light bands alternating with black bands. The antennas also have a light and dark banding;
- There Southern green stink bug it is, however, completely bright green with the anterior portion of the antennae equipped with reddish bands;
- There common green bug It has a green body with a brown membranous base of the elytra (i.e. wings). Furthermore, the entire individual turns dark brown before entering diapause in the winter. The last portion of the antennae has dark bands.
Where do Asian bedbugs come from?
The Asian bedbug originating from eastern Asia, was accidentally introduced into Europe in the 2000s and the first specimens were reported in Italy, in the province of Modena in 2012. It is currently widespread in the United States and in most of the European States and is therefore a species for our territories allochthonous And invasive. The southern green bug Nezara viridula It is now native to North Africa cosmopolitanwhile the common green bug Palomena prasina it’s one European native bedbugdistributed throughout Italy.
What do green and brown bugs eat: damage to agriculture
That of the so-called host plants which they feed on is certainly the most problematic aspect of the presence of bedbugs, considering the extent of the damage they cause to both wild and cultivated plants. Almost all species are phytophagousthey then feed on plant tissues and plant sap by inflicting stings with their type mouthparts biting-sucker. The mandible and maxilla, transformed into thin stylets, penetrate the tissues and inject a saliva containing enzymes that predigest the pulp of fruits and berries, gradually leading them to deformation until complete rotting.
The Asian bedbug is polyphagouscan attack much further 170 species of plants and among these also the fruits of the apple tree, the pear tree and the vine. Indeed, recent studies show that he prefers red grapes over white ones and some vines such as Cabernet and Merlot. The attack on the grape berries negatively affects the aroma and flavor of the must. The Southern Green Stink Bug also feeds on various cultivated species, but i damage is more limited both in extension and in the number of species it can affect. Among these there is certainly the tomato on which it causes punctate necrosis e disgusting taste, the soy pods that shrivel under the effect of the stings and the cabbage that quickly darkens.
Feared in Piedmont and Lazio, the common green bug is mainly the enemy of hazelnut which causes the so-called phenomenon of “bedbug” that is, an organoleptic alteration of hazelnuts that makes them bitter and disgusting.
What is being done to eradicate the Asian bug in Italy
In their countries of origin, Asian stink bug populations are controlled by a number of natural enemies including several species of egg-parasitoid Hymenoptera. Among these, the most famous is the samurai wasp (Trissolcus japonicus), the use of which for the biological fight against the Asian bedbug has also been authorized in Italy starting from 2020. In the meantime, research has also been conducted in Europe on the effectiveness of other parasitoid insects widespread in European territory.
Other methods of struggle involve the use of anti-insect nets on orchards or spraying plants with natural repellents or authorized synthetic insecticides.
An innovative machine, recently tested, the NIR-HSI allows an early verification of the attack of bugs on fruits through the use of infrared rays. Infrared detects necrosis already in the initial phase and before the fruit is completely damaged. This process allows for a rapid sorting of spoiled fruit that is not put on the market.
