Lethal effect of blue light on Liposcelis bostrychophila (Psocoptera: Liposcelididae)

We previously reported that blue light is lethal to various insect species. However, it was also revealed that effective blue light wavelength is species and growth-stage specific. We, therefore, investigated the lethal effects of blue light on booklice, Liposcelis bostrychophila Badonnel (Psocoptera: Liposcelididae), which frequently occur in food processing and storage facilities, where insecticides cannot often be used because of the risk of their contamination on the food products. Liposcelis bostrychophila eggs were killed by irradiation with 408–462-nm blue light and 378-nm UVA at 5 × 10¹⁸ photons·m⁻²·s⁻¹, with 100% mortality. In particular, 420-nm blue light had a strong lethal effect, showing 96.5% mortality at 1.5 × 10¹⁸ photons·m⁻²·s⁻¹. The adults were killed by irradiation with 378–494-nm light at 5 × 10¹⁸ photons·m⁻²·s⁻¹. Irradiation with 378–440-nm and 462-nm light showed 96%–100% mortality at this photon flux density. In particular, 378 and 408-nm light notably exhibited strong lethal effects, showing 100% and 87% mortality, respectively, at 3 × 10¹⁸ photons·m⁻²·s⁻¹. These results show that blue light irradiation is useful for controlling booklice occurrence in food facilities. Additionally, this study revealed for the first time that blue-light irradiation is lethal to hemimetabolous insects.