Currently, we are studying the mechanisms of lethal effects of blue LED Street Light on insects. In the preliminary experiments, we confirmed that the amount of H2O2 in the whole body of Drosophila pupae was increased by blue-light irradiation and showed similar specificity of wavelengths between H2O2 production and lethal effects. In addition, we confirmed that the growth of cultivated cells of Drosophila embryos was suppressed by blue-light irradiation.

In the present study, we investigated the lethal effect of only blue lights because the photon flux densities of green (530 nm), yellow (590 nm), and red (660 nm) lights were less than 10 × 1018 photons·m-2·s-1 at the maximum power. It is thought that the lethal effects of wavelengths of light longer than 530 nm are negligible because these wavelengths were not lethal to Drosophila pupae10 and did not suppress the growth of Drosophila cells in the preliminary experiments.

The wavelengths that are effective against the target growth stage of a target insect should be investigated when using blue light for pest control because the effective wavelength of blue light is species-specific and growth-stage-specific. The wavelength of around 440 nm, which is considered appropriate for irradiation during the egg stage, and that of around 470 nm, which is commonly used in blue LED lights and exhibited a relatively high effect on both the eggs and pupae, are promising wavelengths for controlling the strawberry leaf beetle. In the near future, we will examine the efficacies of LED lights with these wavelengths against beetles in field tests.