The reed-crested glass-winged cicada is spreading at an alarming rate in German growing areas. The insect is increasingly threatening potatoes, sugar beet and other vegetable crops. As reported in the German agricultural newspaper ‘Agrarzeitung’, the situation has worsened in recent weeks. Agricultural associations and experts are now sounding the alarm: there is a risk of massive losses in yield and quality – and so far there is a lack of effective strategies for dealing with the situation. ‘We urgently need solutions to keep infested crops, such as potatoes, in production. Nothing less than food security and the loss of regional cycles are at stake,’ warns Olaf Feuerborn, chairman of the Union of the German Potato Industry (UNIKA).

Joachim Rukwied, president of the German Farmers’ Association, takes a similar view.
In an interview with Welt am Sonntag, he warns about the pest: 'The leafhopper is a real threat to our agriculture and to the security of supply with local food. If we don’t get it under control, there will be a shortage of domestic produce – followed by rising prices.'

The cicada can carry two dangerous pathogens: the Stolbur pathogen and a proteobacterium. These can cause massive losses in yield, quality and storage – up to and including total crop failure in the case of potatoes. The German federal states of Baden-Württemberg, Bavaria and Rhineland-Palatinate are particularly affected. In the case of sugar beet alone, the affected area rose from 40,000 hectares in 2023 to at least 75,000 hectares last year – that's around 20 per cent of Germany's total beet-growing area.

Various emergency approvals issued

As reported by ‘20 Minuten’, the situation has become so serious that the German Federal Office for Food Safety has had to issue several emergency approvals for insecticides. Due to the insect, up to 70 percent of the potato harvest was threatened on various farms. A similar situation is unfolding in Austria, where several plant protection products have also been granted emergency authorisation at short notice. The agricultural associations are also calling for increased research and consistent monitoring to better control the spread of the cicada.

The issue has now reached the political arena. However, there is disagreement on how to solve it. Companies like Bayer and BASF have long developed effective insecticides that are already in use in countries such as Japan, the USA, Canada, and Brazil. In Germany, however, they are only approved in exceptional cases. While farmers criticize this restraint as political negligence, environmental groups insist on maintaining the bans. The question arises: is the fight against the glassy-winged sharpshooter failing because of dogma?

However, in addition to immediate measures, long-term solutions are also needed to combat the cicada. Feuerborn emphasises: ‘A reduction to agronomic or breeding measures is not enough to counter the existential threat to arable farms. We need a strategically coordinated package of measures, even in areas where the cicada does not yet occur.’ The report in Welt am Sonntag puts it succinctly: 'What helps against the leafhopper is not dogma, but technological progress in all its breadth.'

Experts such as Guendel Gonzalez, managing director of Bayer’s German Crop Science division, also criticize the fact that emergency authorizations must be reapplied for every year, offering no planning security – neither for farmers nor for the industry. She calls for a science-based, predictable approval process for new crop protection agents: 'That’s where Europe falls short.'

Switzerland also affected

The reed glass-winged cicada is not only a problem in Germany. The pest is also spreading in Switzerland and is causing significant quality problems, particularly in potato cultivation. Since 2017, there have been reports in western Switzerland of potatoes being threatened by the cicada, and in 2023, the proteobacterium Candidatus Arsenophonus phytopathogenicus was detected for the first time.

‘For the past two years, we have been experiencing more and more quality problems with potatoes, especially with processing potatoes for crisps or French fries,’ says Stefan Vogel, an agronomist and potato researcher at the School of Agricultural, Forest and Food Sciences BFH-HAFL, in a report by ‘SRF’. In Switzerland, yield losses of up to 30 percent are expected.

A current study by the Bern University of Applied Sciences is investigating how the damage to sugar beet can be reduced by crop rotation. Initial results show that the cultivation of SBR-insensitive sugar beet (Syndrome Basses Richesses; Syndrome of low sugar content) and the avoidance of autumn crops such as winter wheat has positive effects. Nevertheless, the challenge remains considerable.

According to Zürcher Bauer, monitoring by the beet advisory service has now detected new infestation areas in German-speaking Switzerland, including the Zurich Weinland region. Researchers therefore recommend strictly implementing crop rotations that interrupt the pest’s life cycle: after sugar beet, a summer crop should follow rather than winter grain. This deprives the larvae of food, causing them to die. A consistent adaptation of crop rotation is, according to Zürcher Bauer, essential to slow further spread.

The effects on the baking quality of potatoes are particularly problematic: in 152 samples tested, 74 per cent tested positive for the proteobacterium. In 21 per cent of the samples, the baking test was insufficient, with different varieties being susceptible to varying degrees. As Vogel explains, this results in an undesirable brown colouring when the potatoes are fried.

Innovative approaches are needed

In a commentary in the agricultural newspaper, German journalist René Schaal sums up the problem: ‘Climate change and globalisation are casting their shadows before them: more and more invasive pests are spreading across German fields.’ The reed-winged glass-winged cicada is not an isolated case. The challenge: effective control is hardly possible.

Increasing regulation and little room for innovation are to blame. ‘Due to ever stricter regulation, the chemical cudgel is hardly available anymore. The number of approved insecticides is gradually decreasing, biological alternatives are still in their infancy, and resistance breeding cannot react quickly enough to the constantly changing threat situation,’ Schaal continues.

The consequence: without fast and sustainable solutions, the cicada will not remain the only threat to agriculture. Farmers need stable framework conditions, research, practical innovative approaches and international cooperation to arm themselves against invasive pests. Schaal mentions specific approaches such as the promotion of natural enemies or genetically modified plants.

One thing is certain: the fight against the reed glass-winged cicada is a race against time that can only be won with the help of effective pesticides. Politicians are now called upon to act quickly. Only in this way can the damage to agriculture be kept to a minimum.