Effect of red LED irradiation, established for control of Thrips palmi in melons and other vegetables, on Frankliniella intonsa density in strawberries

Abstract

Frankliniella intonsa (Trybom) is a major pest in greenhouse-grown strawberries. Although red light-emitting-diode (LED) irradiation of crops suppresses the density of several thrips species, its effectiveness against F. intonsa in strawberries remains unknown. This study aimed to evaluate the effect of a red LED irradiation method, established for controlling Thrips palmi Karny on melons, eggplants, and cucumbers, on the density of F. intonsa on strawberries through greenhouse experiments in 2024 and 2025. Strawberry plants were irradiated with red LED light (peak wavelengths: 620–630 nm in 2024 and 660 nm in 2025) at 1.35–3.79 × 10¹⁸ photons/m²/s. In both years, no significant differences were observed in thrips densities on strawberry flowers between the non-irradiated control and red LED-irradiated plots. In 2024, the cumulative number of F. intonsa adults caught from ethanol-washed flowers was rather significantly higher in the red LED-irradiated plots than in the control plots, whereas no significant differences were observed in 2025. The results indicate that this red LED irradiation method did not suppress F. intonsa density in strawberries. Unlike a previous study, our findings suggest that red LED irradiation did not inhibit the settlement of F. intonsa on the plants. These differences may be attributed to various factors, including the irradiated plant species and their parts, variations in light susceptibility among thrips species, and irradiation intensity and conditions; thus, further investigations are necessary.