Look out, the cicadas are coming!

Two different bacterial pathogens cause SBR (Syndrome Basses Richesses or “low sugar syndrome”) and RTD (rubbery taproot disease). They’re transmitted by cicadas. In addition to sugarbeet, other crops, especially potatoes, and some vegetables can also be infected.

Cicadas – in Germany and Western Europe the reed glass-winged cicada – fly into sugarbeet fields from the end of May to the end of July, suck on the plants and transmit the pathogens. The symptoms become visible from mid-August: SBR-infected plants exhibit yellowed leaves and significantly reduced sugar content, hence the name of the disease. In the case of RTD, the leaves turn yellow and die. In addition, the bacteria deprive a beet of water, causing its body to become rubbery. As a result of the infestation, yields drop sharply, while storability and processing in the sugar factory are hugely impaired. In contrast to Germany, in Southeastern Europe a slightly different glass-winged cicada transmits the bacteria, which is why the RTD disease mainly occurs there. A total of around 150,000 hectares are affected in Europe – and the disease continues to spread.

Breeding of tolerant varieties

At KWS, breeding new varieties that are tolerant to both diseases is currently a top priority. SBR has only been widespread for a few years, so intensive breeding trials have only recently become possible. The pathogen that causes RTD has even been known for only a few years. That’s why KWS has built up testing capacities and significantly increased investment in the relevant breeding programs in recent years. This year, we’ve already tested several thousand genotypes in field trials for tolerance to SBR and RTD. In addition, internal yield trials have been expanded to over 10,000 plots at locations in high-infestation areas. Thanks to these efforts, the first robust varieties for SBR are now available in the shape of MARABELLA KWS and JOSEPHINA KWS, which deliver high yields even in the event of infestation.

In addition to breeding of tolerant varieties, agronomic approaches are also needed to control the disease complex in the long term. The cicada’s lifecycle is adapted to winter wheat after sugarbeet, as a typical crop rotation. This allows the cicada’s offspring to continue their lifecycle in winter wheat during the winter months and fly from the wheat to new sugarbeet fields the next year. In the short term, adapting the crop rotation can interrupt the lifecycle. However, as the sugarbeet-winter wheat crop rotation is economically attractive, field trials are being conducted to investigate whether the lifecycle of cicadas can be interrupted in winter wheat using biological and synthetic seed treatments.

The timing of flight is key

For established diseases, farmers know when agronomic control measures are necessary. However, SBR and RTD are relatively new disease complexes, so this knowledge is still lacking. For the development of new insecticide strategies, we’re systematically investigating the interaction between plants and cicadas. In field trials, we cover plots with nets before the cicadas begin flying in order to prevent infection. During the flight phase, we temporarily open individual nets for defined periods of time. This allows us to determine the period in which the cicadas cause the greatest yield losses, thus enabling targeted and effective measures to combat them.

KWS already offers a wide portfolio of information to share initial findings from the trials. In line with our #YourSeedPartner strategy, we are there to help farmers overcome this challenge hand in hand. |