Drought-Stressed Plants Emit Sounds That Guide Moth Egg-Laying Choices

Research published on November 14 via bioRxiv has indicated that ultrasonic sounds produced by drought-stressed plants may play a role in the egg-laying decisions of female moths. It has been suggested that these high-pitched noises, undetectable by humans, are evaluated by moths to avoid dehydrated plants when selecting suitable hosts for their caterpillars.

The study was led by Rya Seltzer, an entomologist from Tel Aviv University, whose team investigated whether the ultrasonic clicking sounds of stressed plants could influence the behaviour of the Egyptian cotton leafworm moth (Spodoptera littoralis), as per a report by The New York Times. Experiments were conducted in controlled environments where moths were exposed to speakers emitting sounds mimicking those of dehydrated tomato plants. It was reported that in the absence of real plants, moths laid eggs closer to the speakers emitting these sounds.

Observations with Live Plants

In subsequent experiments, live tomato plants were introduced, with one side of the test arena containing a hydrated plant and the other a water-stressed plant. Moths were observed laying eggs more frequently on the healthier plants. A further setup involved placing hydrated plants on both sides while one side emitted artificial stress sounds. The moths were found to favour the silent plants over those accompanied by simulated stressed plant noises.

According to the researchers, this indicates that moths not only detect these ultrasonic signals but associate them with the physiological condition of the plants. It was further noted that moths raised entirely in laboratory conditions, with no prior exposure to plants, displayed this behaviour, highlighting its genetic foundation.

Implications for Pest Management

Biologist Björn Thorin Jonsson from the University of Graz told NYT that widespread and reliable acoustic cues could be utilised by insects to locate better resources. Fernando Montealegre-Zapata, a sensory biologist at the University of Lincoln, suggested that these findings could hold applications in agriculture. He questioned whether stress sounds could be employed to deter pests from laying eggs on healthy crops.

Rya Seltzer told the publication that this discovery may represent only the beginning of uncovering acoustic interactions between plants and insects. It was proposed that similar behaviours might be widespread among other insect species, with potential implications for ecological research and agricultural innovation.