A female moth wanders through a Tel Aviv greenhouse. She has two choices: a thriving tomato plant and one starting to dry out. To you, they look the same, but she hears something you can't hear. Small ultrasonic clicks, like popcorn popping, come from the thirsty plant. So she suddenly turns around and leaves.
It's not instinct; it's a reasoned decision based on acoustic information we're just beginning to understand. For the first time in history, scientists have demonstrated that a true sonic dialogue exists between plants and insects.
Moths listening to the silent cry of plants
The team led by Rya Seltzer e Guy Zer Eshel ofTel Aviv University has published results that change the way we view communication in nature. The study, published in the journal eLife, shows that female moths of the species Spodoptera littoralis (commonly known as Egyptian cotton moths) They are able to perceive and respond to ultrasonic sounds emitted by plants under stress.
When a tomato plant starts to dehydrate, its vascular system produces distinctive ultrasonic clicksThese sounds, generated by cavitation in the xylem (the tubes that transport water from the roots to the leaves), are completely imperceptible to the human ear but fall perfectly within the frequency range audible to moths. Nature, as always, proves more sophisticated than we imagined.
The research builds on a previous discovery by the same team, which had already demonstrated how Plants under stress emit ultrasound that many animals can perceive.This time the researchers went further, demonstrating that these sounds are not just “heard,” but actively used to make crucial decisions.
The experiment that changed everything
The scientists designed a series of ingenious tests to isolate the acoustic component from all other factors. In the first experiment, they presented female moths with two boxes: one silent and one containing a speaker playing recordings of a dehydrated tomato plant.
The result was surprising: the moths showed a clear preference for the “noisy” box, probably interpreting those clicks as a signal of the presence of a living plant, albeit one in distress. However, when the researchers impaired the moths' hearing, this preference disappeared completely.
But the real twist came in the second experiment. When the moths were presented with two real, healthy tomato plants, one accompanied by a speaker emitting stress sounds, they unequivocally chose the silent plant. As the researchers explain: “The females' egg-laying preference shifted toward the side without the acoustic signal.”.
This seemingly contradictory behavior actually reveals a sophisticated decision-making mechanism. As I told you in this article on plant communicationPlants use multiple channels to "talk" to their surroundings. Moths, for their part, integrate acoustic, visual, and olfactory information to make the best choice.
Why moths developed this ability
The answer lies in the reproductive biology of these insects. Female moths must carefully choose where to lay their eggs, because the survival of their offspring depends on that decision. A healthy plant will provide abundant food for the larvae when they hatch. A stressed or dying plant, however, could doom them.
Ultrasonic hearing in moths evolved primarily for two reasons: detecting male courtship signals and escaping predatory bats that use echolocation. But nature, with its ability to optimize, has allowed these insects to exploit the same sensory equipment for a third purpose: evaluate the quality of host plants through their ultrasonic “cries”.
This is the first documented case of an animal responding to the sounds produced by a plant. It's a vast unexplored area, an entire world waiting to be discovered.
As Professor points out Yossi Yovel, co-author of the study, many mammals and insects can hear ultrasonic frequencies. If they also use plants' acoustic signals to guide their behavior, we may be witnessing a much more widespread phenomenon than we imagined.
From moths to the agriculture of the future
The practical implications of this discovery go far beyond pure biology. Farmers may one day use ultrasonic sensors to detect water stress in crops early, intervening before problems become visible to the naked eye. Tomato plants, for example, begin emitting stress signals before showing obvious signs of dehydration.
The team has already developed a patent for irrigation systems based on this acoustic information. As I explained to you when talking about the intelligence of plants, the plant world continues to surprise us with capabilities that challenge our traditional conceptions.
This research also opens new avenues for biological pest control. If moths actively avoid plants that emit stress signals, it may be possible to develop systems that "trick" pests into thinking crops are in poor condition.
Researchers are cautious about calling this phenomenon “communication” in the strict sense. The sounds emitted by plants are likely a byproduct of physical stress, not signals evolved specifically to communicate with insects. However, the interaction is real and functional.
This discovery reminds us how much we still have to learn about the mechanisms of communication in nature. We live immersed in a world of signals we cannot perceive, where plants and animals exchange information through channels we have only just begun to decipher. Moths, with their ability to "listen" to the plant world, are teaching us that nature is much more connected and communicative than we ever imagined.
The next time you see a moth flitting around your garden, remember that it's not just flying around at random. It's listening in on a conversation that we, for now, can only watch as spectators.
