Harvest increasingly at risk This insect threatens Swiss potatoes

Farmers in southern Germany and Switzerland are facing a new challenge: The reed glasswing cicada transmits bacteria that endanger the potato harvest.

In southern Germany and Switzerland, farmers are facing an ever-increasing challenge: The reed glasswing cicada, a small insect, is increasingly threatening the potato harvest.

This insect transmits bacteria that cause the syndrome of low sugar content (SBR), which previously mainly affected sugar beet. For about two years now, however, the bacterium has also been detected in potato plants and is spreading rapidly. Also in Switzerland.

Crop loss of over 50 percent

The situation in Germany has worsened in recent years. Regions where potatoes and sugar beet are grown consecutively in a crop rotation are particularly affected. If potato plants are infested, farmers are threatened with a crop loss of over 50 percent, sometimes even a total loss.

The effects are also being felt in Switzerland. "For the past two years, we have had increasing quality problems with potatoes, especially with processing potatoes for chips or French fries," says Stefan Vogel, agronomist and potato researcher at the Bern University of Applied Sciences (BFH), to "SRF". It is strongly assumed that the reed glasswing cicada plays a role here, but many details still need to be clarified.

The reed cicada only causes damage when it transmits certain bacteria such as "Arsenophonus" or "Phytoplasma solani".

The former causes the sugar content in beets to drop and the starch content in potatoes to decrease. The second bacterium causes the roots of the plant to die. As a result, the potatoes no longer get enough water and shrivel up. However, the exact chemistry behind the processes is still being researched.

Yield losses of up to 30 percent in Switzerland

Vogel expects yield losses of up to 30 percent in Switzerland. The baking quality of processing potatoes is particularly problematic. When the potatoes are fried, they turn an undesirable brown color.

"As a result, fewer Swiss products are coming onto the market and more foreign chips and potato chips are being sold in Switzerland," says the agronomist.

As a temporary measure, experts recommend that farmers use crop rotation to contain the cicadas: After the cicadas have laid their eggs on sugar beet, the hatched nymphs also feed on the following crop, in our case winter wheat. However, if this is not cultivated but left fallow, the young animals can no longer feed and die before a spring crop is planted.

However, different and long-term solutions are needed to meet the challenges in potato and sugar beet cultivation.