"Stopping Pests with 'Bat Sounds'? New Agricultural Tech Uses Ultrasound to Prevent Moth Egg-Laying: The Power of Ultrasound Demonstrated by Chiba University"

Pest Control Just by Playing "Sounds"?

"The era of stopping pests with 'sound' instead of pesticides might be coming."

Such a seemingly science fiction-like research finding has been reported by a team from Chiba University and the National Agriculture and Food Research Organization. The theme is the "silent war" between moths flying around the fields at night and the bats that prey on them. By playing ultrasonic sounds similar to bat calls from speakers, a certain type of moth stops flying, which could potentially reduce the next generation that feeds on crops.Phys.org

The research findings have been published in the international journal of pesticide science, Pest Management Science, and have been disseminated worldwide through Phys.org and the English site of Chiba University.Phys.org

Bats vs. Moths: A 60-Million-Year "Arms Race"

For nocturnal moths, "listening" is a lifeline. Bats, flying at high speeds in the dark, emit ultrasonic sounds and read the reflections to accurately locate moths. When moths detect this sound, they have survived by making sharp turns, flying in zigzags, and even evolving their wings and body shapes to deflect sound waves.Phys.org

The research team focused on this endless "coevolutionary arms race" between the two. This time, they closely examined how the agricultural pest Autographa nigrisigna, which is widely distributed from East Asia to South Asia, distinguishes bat ultrasounds.CHIBADAI NEXT

Experiment: Artificially Reproducing Bat "Conversation Speed"

Bat ultrasound is not just a simple "beep" sound. When searching for prey, it is slow, but just before capturing, it becomes a very rhythmic signal, like a machine gun with rapid "tat-tat-tat" sounds. The number of pulses per second is called the "Pulse Repetition Rate (PRR)."Phys.org

The research team prepared 100 adult moths (50 males and 50 females) and observed their reactions to artificial ultrasounds with different PRRs. The PRRs set were broadly in three stages.CHIBADAI NEXT

• Low speed: 1, 5, 10 Hz
  The stage where bats are still leisurely exploring for prey.

• Medium speed: 20, 40 Hz
  While closing in on the moth.

• High speed: 80, 160 Hz
  Just before predation, the so-called "terminal buzz."

The results were very clear. With low-speed sounds, the moths only took simple evasive actions, like slightly changing direction. However, at medium speed, their flight became irregular, and at high speed, many individuals stopped flying as if they were "frozen."Phys.org

Why Females Carrying Eggs Become More "Fearful"

The research team also focused on females carrying eggs (gravid females). When exposed to the same ultrasound, they reacted more strongly than unmated individuals and were more likely to stop flying at high PRRs.Phys.org

This reveals the moths' decision-making process of weighing **"life" and "offspring."**

• If they are preyed upon while carrying eggs, both they and the eggs are lost.

• Therefore, it is more prudent to protect themselves by giving up moving or laying eggs the moment they judge the danger to be high.

Indeed, when counting the number of eggs laid within a certain period, there was a tendency for the group exposed to high PRR to lay fewer eggs, confirming the flow of "hearing dangerous sounds" → "not flying" → "fewer opportunities to lay eggs."CHIBADAI NEXT

Potential and Challenges of "Ultrasonic Speaker Farming"

If this characteristic can be effectively utilized, small ultrasonic devices could be installed in fields to play sounds similar to the bat's "terminal buzz" at night, potentially reducing the time moths fly around and consequently suppressing the number of eggs laid. The research team also points out that introducing ultrasonic emitters could suppress nocturnal moth activity and lead to a reduction in pesticide use.Phys.org

The benefits compared to traditional chemical pesticides can be summarized as follows:

• Reduced environmental impact: No residues in soil or water systems

• Target specificity: The possibility of targeting only the PRR disliked by specific moths

• Less likely to cause resistance issues: Less evolutionary pressure like that from pesticide resistance

On the other hand, there are also several challenges.

1. Will it work the same outdoors?
   The experiments were conducted in a controlled indoor environment, and further verification is needed to see how effective it will be in fields with wind and other sounds.Phys.org

2. Impact on other creatures
   Although ultrasonic sounds are hard for humans to hear, other animals besides bats can detect them. It is necessary to determine frequencies and outputs that do not adversely affect predators or beneficial insects.

3. Cost and operation
   How many speakers to install depending on the size of the field, how to secure power, and whether to change sound patterns depending on the season and crops are themes that need to be addressed from a practical perspective.
   
   
   

What kind of reactions might appear on social media

This research finding has been covered by science news sites like Phys.org and EurekAlert!, and the press release has been shared from EurekAlert!'s official X (formerly Twitter) account.Phys.org

At present, it feels like the "pre-buzz" stage, but when such news circulates on social media, comments of the following types tend to appear. Here, we will organize the "atmosphere" of typical reactions rather than actual examples of posts.

1. Voices welcoming the reduction of pesticides

From environmentally conscious users,

"If this becomes practical, it seems like pesticides could be significantly reduced."
"Organic farming + ultrasonic speakers seem like a good match."

Such hopeful comments are likely to emerge. In Japan, where neonicotinoid pesticides and their impact on biodiversity are frequently discussed, many people might intuitively have a positive impression, thinking "sound might be safer."

2. Concerns about "unforeseen" impacts on ecosystems

On the other hand,

"If bat sounds are played 24/7, won't real bats get confused?"
"It might affect not just moths but other insects and animals too."

Cautious opinions like these will inevitably appear. Since ultrasonic sounds are invisible, the fact that "it's hard to understand what's happening" tends to be a source of anxiety. Researchers must also evaluate the impact on non-target organisms.

3. Simple questions and light-hearted jokes

Furthermore, simple questions from the perspective of general users are sure to fly around.

• "Can humans really not hear it? Are pets okay?"

• "If I play it on my balcony, will the night insects quiet down...?"

• "I wish ultrasonic sounds could also make mosquitoes go away."

Some might even post jokes like "better than the neighborhood kids' screams."

The Future Vision of Researchers: A New Piece for IPM

Professor Masafumi Nomura of Chiba University specializes in "pest management with low environmental impact (IPM: Integrated Pest Management)" and has taken an approach that combines natural enemies, lighting, and physical controls like this study.CHIBADAI NEXT

The method using ultrasound can be said to add a new piece to the IPM puzzle.

• Biological control with predatory insects during the day

• Attracting adults with pheromone traps in the evening

• Suppressing flight and egg-laying with ultrasonic speakers at night

If such "multi-layered defense by time of day" can be realized, it might lead to much more sustainable and risk-diversified pest management than relying on a single pesticide.

The "Silent Story" of Bats and Moths Could Change the Future of Fields

This research is just the first step towards practical application. However, inspired by the "predator-prey interactions that have unfolded in the night sky," a path is opening to make human agriculture gentler and smarter.Phys.org

Perhaps in a few years, when driving past fields at night, small speakers quietly emitting ultrasound in the silent darkness might be engaging in "silent negotiations" with the moths.##