In order to keep insect pests away from cultivated areas, researchers proposed, as early as the 1960s, to broadcast ultrasound imitating those emitted by bats to locate their prey. But the attenuation of the signal in the atmosphere makes this repellent system unsuitable for large areas, so it has not been properly evaluated. A Japanese team believes, however, in PNAS of October 10, that the method could work on smaller plots and in greenhouses. Ryo Nakano (Tsukuba Plant Protection Institute) and his colleagues first tested different artificial ultrasounds mimicking those of bats in the hunting phase to determine those to which the striped moth, a caterpillar moth from Asia gluttonous, was sensitive. They then carried out full-scale tests, which confirmed the effectiveness of the process.
The army moth frightened by ultrasound
Insectivorous bats and moths are engaged in an arms race. The former to locate their meal by echolocation by emitting ultrasounds, the latter by carrying out avoidance maneuvers or by dropping to the ground as soon as they perceive this signal.
1 Eardrums on the chest
The striped fruitworm (Spodoptera litura) is one of approximately one hundred thousand species of moths with eardrums located on the thorax. A Japanese team measured the ultrasound frequencies to which the nerve cells connected to these membranes were sensitive and, in the wind tunnel, specified those which caused the flapping of the wings to stop.
2 Add sound to the plots
Scientists tested the repellent effectiveness of artificial ultrasound on onion plots and greenhouses with strawberries, to measure the best arrangement of transmitters and ensure that the signal spreading over a long period would not lead to a habituation of insects.
3 Promising results
Japanese researchers have observed a drop in cutworm egg laying. They estimate that the bats will find their pittance at the edge of the protected plots. And stipulate that the spreading of pesticides had to continue there to fight against other pests.
Source : Nakano et al., PNAS 2022.