Ultrasonic Distress Signals: How 'Screaming' Plants Deter Moths from Laying Eggs

Understanding Plant Communication: New Insights into Acoustic Signals

Plants, though lacking a nervous system, have evolved remarkable mechanisms to communicate stress—one of which operates via ultrasonic sound waves inaudible to humans. Recent research from Tel Aviv University has unveiled a fascinating link between these imperceptible plant distress signals and the reproductive behaviors of insects, fundamentally expanding our understanding of plant-animal interactions.

The Scientific Context: Discovering Plant Ultrasound

For years, scientists have recognized that plants under environmental duress, such as drought or physical injury, release chemical signals or visual cues. Building on this foundation, groundbreaking studies have demonstrated that plants—in particular, tomato plants—emit high-frequency ultrasonic “clicks” when stressed by dehydration or damage. These plant-generated sounds, recorded at frequencies above human hearing, prompted researchers to question whether any animals in a shared ecosystem could perceive and respond to these cues.

Experimental Approach: Moth Response to Plant Distress Calls

To probe this question, a team led by zoologist Yossi Yovel and evolutionary biologist Lilach Hadany designed a set of experiments featuring the Egyptian cotton leafworm moth (Spodoptera littoralis), a common agricultural pest known for laying eggs on plant hosts. Female moths were observed for their egg-laying preferences across various scenarios that mimicked the acoustic signature of plant stress.

< h4> Detailed Experimental Setup and Tests

In the first experiment, moths were given a choice between two boxes—one silent, and one playing recorded ultrasonic emissions from a dehydrated tomato plant. Fascinatingly, moths consistently preferred the box with the ultrasonic plant noises, interpreting these sounds as potential plant hosts. When the moths’ auditory organs were disabled, their ability to choose an egg-laying site became random, revealing the critical role of acoustic cues in their decision-making.

A second trial tested whether moths would discriminate between healthy and stressed plants based on sound. Two identical, healthy tomato plants were presented; however, one was accompanied by a speaker replaying distress signals. In this scenario, female moths overwhelmingly favored the silent plant—indicating a refined preference for depositing eggs only on healthy, non-stressed hosts likely to better nourish their larvae.

In a third control experiment, researchers replaced plant sounds with ultrasonic mating calls from male moths. The lack of a distinct moth preference suggested that the insects’ selective behavior was specific to plant-produced ultrasonics, rather than any generic high-frequency sounds.

Key Discoveries: Animals Eavesdrop on Plant Signals

The Tel Aviv University study provides the first empirical evidence that moths and potentially other insects can perceive acoustic emissions from plants and use these cues to guide crucial life choices. This opens an intriguing window onto the hidden complexity of ecosystems: plants acoustically ‘announce’ when they are under threat, and insects listen, adjusting behaviors such as egg-laying in direct response. As Yovel explains, "We hypothesized that if insects could hear these sounds, they might make eco-logical decisions accordingly. This research confirms that such eavesdropping exists in the natural world."

For plants, emitting ultrasonic signals may serve as a survival strategy, subtly influencing the behavior of both herbivores and beneficial pollinators, while for insects, finely tuned hearing provides adaptive advantages when selecting environments for their offspring.

Broader Implications and Future Prospects

These findings not only deepen our understanding of plant bioacoustics and interspecies communication but also suggest new possibilities for sustainable pest management. By manipulating or mimicking plant distress signals, farmers might one day influence pest behaviors and protect crops without extensive chemical intervention.

Furthermore, this study hints at a much broader tapestry of sonic signaling in nature, not just between plants and insects but potentially among plants themselves. As the authors suggest, the world of plant-generated acoustic signals is just beginning to be charted—and more hidden interactions may await discovery.

Conclusion

This pioneering research from Tel Aviv University evidences that ultrasonic distress emissions from plants can deter moths from laying eggs on stressed hosts, fundamentally reshaping our picture of plant-insect communication. By uncovering these sophisticated acoustic interactions, scientists move closer to decoding the silent language plants use to manage their ecological relationships—and the opportunities such discoveries may bring for both biodiversity conservation and agricultural innovation.