Until recently, the reed leafhopper fed exclusively on reed grass. But now it also attacks crops such as sugar beets, potatoes, carrots and onions. Biologists have now traced how it managed to develop into an agricultural super pest. Accordingly, the cicada currently lives in symbiosis with seven types of bacteria, which enable it to attack various plants. However, at least two of these microbes can also transmit plant diseases and thus lead to significant crop losses. The knowledge could now help to regulate the spread of the cicada via its bacterial inhabitants.
Originally, the reed leafhopper (Pentastiridius leporinus) was a highly specialized insect that only ate reed grass. Due to this restriction, the insect was threatened with regional extinction in Germany. In recent years, however, the cicada has evolved so much that it now also attacks root vegetables such as sugar beets, potatoes, carrots and onions. It has also conquered grains such as winter wheat and spring barley as well as perennial plants such as asparagus and rhubarb as new host plants.
The cicada only causes minor damage to the individual plants. Nevertheless, it is now a dangerous pest and feared enemy of farmers in Europe. The native insect transmits two bacteria that cause the plant diseases SBR and Stolbur and lead to massive crop failures – especially in sugar beets and potatoes.
Seven microbial residents
But why was this insect able to spread so widely and what role did its microbial inhabitants play in expanding its diet? Researchers led by Heiko Vogel from the Max Planck Institute (MPI) for Chemical Ecology in Jena have now investigated this. To do this, they took samples from different places on the bodies of three cicadas and analyzed which microbes live there.
The surprising result: The reed leafhopper harbors not just two, but at least seven different types of bacteria. The researchers confirmed two of them in the samples as the two already known bacterial species that transmit the plant diseases SBR and Stolbur. Accordingly, the culprits are Candidatus Arsenophonus phytopathogenicus and Candidatus Phytoplasma solani.
In addition, the team found five other species of bacteria in different parts of the reed leafhopper’s body. “It seems to be absolutely dependent on three of them. These symbionts live in specific organs and are passed on from generation to generation via the eggs. They contribute to the cicada’s nutrition by producing ten essential amino acids and B vitamins,” reports Vogel. These three bacteria come from the genera Purcelliella, Karelsulcia and Vidania and, with their metabolic products, supplement the nutrients that the cicada itself receives from the plant juices, as the team found.
The function of the bacterial partners should be further researched
“The significance of the two remaining bacteria for the insect host remains unclear,” says Vogel. These microbes are representatives of the genera Rickettsia and Wolbachia. These could also transmit diseases, as some tests suggest. In general, all symbiosis partners could have helped the reed leafhopper to adapt to the diverse defense mechanisms of its host plants. The team suspects that the bacteria could, for example, produce antidotes to plant toxins or bypass the plants’ immune defenses. This ultimately enabled the cicada to transform from a picky reed grass specialist to a multi-plant connoisseur. However, exactly how this development into an agricultural super pest took place is still unknown.
With knowledge of the symbiosis partners, targeted strategies can be developed in the future to control the spread of the reed leafhopper. This could promote beneficial bacteria and combat harmful ones instead of fighting the cicada itself. One approach also involves manipulating the cicadas’ saliva to prevent the harmful bacteria from being transmitted to crops. However, follow-up studies should first investigate the exact role and interactions of the individual microbial partners of the reed leafhopper.
Source: Max Planck Institute for Chemical Ecology; Specialist article: mBio, doi: 10.1128/mbio.03103-25