The Italian region of Emilia Romagna has started an experimentation for the biological pest control of the brown marmorated stink bug – which destroys agricultural crops and fruit plants – by contrasting the insect with the introduction of the samurai wasp.
Halyomorpha halys is a parasitic insect endemic of China and Japan. It has probably arrived in Italy from the United States and it causes great damage to crops and fruit plants.
The mouth of the brown stink bug ends with a proboscis that allows the insect to pierce the plant tissue in order to suck its fluid and leave the rest of the crop dimpled or necrotic. This parasite is extremely dangerous in that it proliferates by depositing eggs at least twice a year, each time producing around 400 bugs.
In Italy the stink bug has no endemic predators. As a consequence, the samurai wasp – which does not harm human beings – had to be imported from Asia.
In 2020 around 66 thousand specimens of samurai wasp (Trissolcus japonica) have been introduced in hedges, green areas and woodlands where the brown marmorated stink bug typically lays eggs.
As a matter of fact the samurai wasp does not feed on bugs themselves but it inserts its larvae into the bug’s eggs, thus making the bug’s eggs harmless. The regional phytosanitary service has made some observations in the areas where the wasps had been introduced in order to verify the validity of the experimentation: the first results show that the index of efficacy stands around 5.6% (that is to say, the wasp has invaded 5 eggs on 10). At the moment no collateral damages to the environment have been registered.
The regional project of biological pest control towards the brown marmorated stink bug has been made possible thanks to the cooperation of various bodies: the regional phytosanitary service, Modena’s phytosanitary service, the council for the research in agriculture and the analysis of agricultural economy, the University of Bologna, Modena and Reggio Emilia and some technicians from the main horticultural organisations of the Emilia Romagna region.
Samurai wasp – Photo: Science
It is interesting to note how in order to create a big number of lab-grown samurai wasps a lot of stink bug’s eggs are needed, which means that thousands of stink bugs have to be grown as well in laboratories.
