That animals communicate with each other is something we take for granted. But plants also possess a sophisticated warning system – they emit scents to alert other members of their species to danger. An international study led by the University of Neuchâtel and Hangzhou Normal University, published in January 2026 in the renowned journal PNAS , now shows for the first time how tomato plants use this ability to defend themselves against viruses. The discovery could fundamentally change agriculture.
The threat: Tiny insects with devastating effects
The threat comes from an inconspicuous insect: the whitefly ( Bemisia tabaci ). This tiny creature, only a few millimeters long, is one of the most dangerous agricultural pests worldwide. It not only sucks plant sap but also transmits begomoviruses – including the tomato yellow leaf curl virus (TYLCV), which can destroy entire tomato harvests.
The figures are alarming: In 2023 alone, whitefly viruses caused economic damage of nearly 100 billion yuan (approximately 13 billion Swiss francs) in China. Worldwide, these pests threaten numerous crops, including tomatoes, cotton, and cassava.
The close symbiosis between insect and virus is particularly insidious: the viruses multiply not only in the plant but also in the body of the whitefly. Infected insects are more efficient vectors and infest more plants – a perfidious mechanism that dramatically accelerates the spread of the disease.
The discovery: A fragrance as an alarm signal
Researchers led by renowned plant ecologist Ted Turlings from the University of Neuchâtel and Chinese scientist Zhang Pengjun made a remarkable discovery. They found that tomato plants infested with virus-carrying whiteflies release a very specific fragrance: beta-caryophyllene . This volatile compound is a sesquiterpene hydrocarbon molecule found in many plants.
Important: The alarm signal is triggered much earlier and more intensely if the attacking insects actually carry viruses. The plant thus distinguishes between "harmless" and "dangerous" enemies – and reacts accordingly.
The message is getting through: What the neighboring plants are doing
Neighboring plants perceive this scent through their leaves and react immediately. They then enter a state of heightened alertness, which experts call "priming." This means: They are not yet producing expensive defense substances, but are now ready to react instantly in the event of an actual attack.
The research results reveal two specific protective mechanisms. :
1. Activation of the virus defense
The warned plants activate their immune system against the viruses. If a virus-carrying whitefly later feeds on them, they can suppress the replication of the viruses in their tissue much more effectively. They are resistant to the disease.
2. Attracting helpers
In addition, the warned plants begin to release further aromatic compounds – including methyl salicylate and beta-myrcene. These substances act like a distress signal: they attract tiny parasitic wasps ( Encarsia formosa ), which are natural enemies of the whitefly. These beneficial insects lay their eggs inside the pest larvae, thus killing them. The plant is essentially summoning its own "bodyguards."
The double benefit: How the plant breaks the virus-insect alliance
What's particularly fascinating is the strategic effect of this warning system. By alerting their neighbors, the tomato plants break the dangerous alliance between virus and insect. :
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The neighboring plants become resistant to the viruses – the virus can no longer multiply.
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At the same time, they become less comfortable for the whitefly (due to the attracted parasitic wasps).
The researchers were able to confirm this effect experimentally. They used both synthetic beta-caryophyllene and genetically modified tomato lines that produced more of this aromatic compound. In both cases, the treated plants showed significantly improved resistance to the viruses and better protection against insects. .
Not every tomato variety can warn you.
A key finding of the study: Not all tomato varieties possess this ability. The researchers tested various cultivated and wild tomato varieties and found significant differences in the production of beta-caryophyllene. .
This finding is of great importance for agriculture. It opens up the possibility of specifically breeding or cultivating tomato varieties that are particularly "communicative" and can effectively warn their neighbors.
Perspectives for agriculture
The study, which also involved researchers from Hangzhou Normal University and Chongqing Normal University, received funding from the National Natural Science Foundation of China and Zhejiang Province. It is a prime example of successful international cooperation.
The practical applications are obvious:
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Breeding : Selection of tomato varieties with high beta-caryophyllene production
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Plant protection : Use of synthetic fragrance dispensers in fields to activate the plants' defenses.
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Integrated cultivation : Combination with beneficial insects (parasitic wasps) for natural plant protection
Ted Turlings, one of the study's lead authors, emphasizes: "Our discovery reveals a previously unknown level of plant communication. The plants prioritize their defenses strategically – they protect themselves first against the viruses that pose the greatest long-term threat." .
Conclusion
The discovery that tomato plants can warn their neighbors of viruses via scent and even attract beneficial insects is a milestone in plant research. It demonstrates how complex and sophisticated nature's survival strategies are. At the same time, it opens up entirely new avenues for sustainable plant protection that does without chemical pesticides – a major benefit for both the environment and agriculture.
The study provides further evidence that plants are by no means passive organisms, but actively communicate and help each other. What sounds like a scene from a fantasy film is scientific reality: The tomatoes in the field warn each other when danger threatens.
