Here in Switzerland we eat a lot of chestnuts every year in the form of desserts such as vermicelli or roasted on a grill and sold on street corners.
But an invasion of an oriental gall wasps “Dryocosmus kuriphilus”, originally from Asia, has depleted yields since about 6 years. In the Italian part (Ticino) of Switzerland, the harvest yield fell from 60 tons to a few hundred kilos between 2006 and 2014. The gall wasps arrived in Switzerland from Italy and began affecting harvests in the cantons of Ticino, Valais and Vaud. The gall wasps attack checkout trees, weakening the tree and reducing its foliage without actually killing it. One solution is to introduce another Asian wasp, “Torymus sinensis”, which is a natural enemy of the gall wasp.
This insect has already surfaced in Italy, where it has a beneficial impact on the chestnut harvest.
It is not permitted to import the gall wasp’s natural enemy into Switzerland but the wasp does not know our immigration regulations ;-) and has already begun to cross the Swiss border.
Chestnut trees near the Italian border produced a better harvest this year and the situation relaxes.
It will take a long time until the harvest yields are back on the former quantities. So sweet chestnuts are an expensive delicacy here. But sooooooooo delicious.
I personally am a little ambivalent about the “use” of invasive species (Neobiota) who were brought to an ecosystem by humans where they have not existed before. But who am I to rate something like this...
