Probably not so great for the growers but they'll adjust.
Either voluntarily or through bankruptcy. That's how commodities markets work.
From The Economist, February 16:
Culture | Playing the tuber
Like chips and pancakes? Lucky you
THEy are calling it the Kartoffel-Flut: the potato flood. Germany, the largest producer of spuds in the European Union, is enjoying the biggest harvest in a generation, owing to optimal growing conditions and increased tuber cultivation. Last year’s yield was 17% higher than the long-term average. Belgium, France and the Netherlands have also had a bounty.
In fact, there are so many potatoes—one farm near Leipzig had a surplus of 4,000 tonnes—that they are being given away. Some 200 distribution points have been set up across Berlin. Gasthaus Mutter Hoppe, a restaurant, had a tonne of taters to dish out; a waitress says they “ran out within days”. The Berliner Tafel, a food bank, took 22 tonnes. Schools, homeless shelters and even the zoo have stocked up.
If you were to have an abundance of any crop, you would pick the potato. Not only does it store well, but it is filling and calorie-dense relative to other vegetables. It also lends itself to an extraordinary variety of meals. Germans are making potato dumplings and pancakes. The organisers of the giveaway have launched a recipe challenge to inspire Kartoffel cooks, sharing tips for soups, salads and plenty more. As Sam memorably says in “The Lord of the Rings”, you can “boil ’em, mash ’em, stick ’em in a stew!”....
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You can order up some Pommes Duchesse, just be sure to have a defibrillator nearby.
Possibly also of interest:"How Antoine Augustin Parmentier Tricked The World Into Loving Potatoes"