Effects of timed LED regimes on tomato plant traits, performance of two-spotted spider mites, and predatory mites (Phytoseiulus persimilis)

Background: Light-emitting diodes (LEDs) are being used in controlled environments to enhance crop production and pest management with most studies focusing on continuous treatments (applied throughout the entire daytime or nighttime period). Here, we tested the hypothesis that providing tomato plants with timed LED regimes (daily 3-h doses of red, blue, or far-red LED) during the day or at night may affect their traits (leaf reflectance indices, element composition, and phenolic profile), performance of two-spotted spider mites (Tetranychus urticae) (TSSM), and a species of predatory mite (Phytoseiulus persimilis).

Results: Nighttime LED regimes significantly altered leaf element composition: red LED increased K levels, blue LED enhanced Mg levels, and far-red LED enhanced Mn and Cu and reduced Zn levels. Among daytime LED regimes, blue LED reduced Zn level. Nighttime LED regimes significantly increased leaf glandular trichome densities (except far-red regime) and reduced total phenolic content. Among a series of leaf reflectance indices, ARI and CRI increased significantly in response to nighttime red and blue regimes but decreased with far-red LED regimes. Performance bioassays showed significantly lower TSSM populations on nighttime plants than on daytime and control plants. LED regimes did not affect predatory mites' population and their feeding capacity, except for blue daytime regime, which was reduced on mobile TSSM. These results suggest that timed LED regimes have potential to strategically manipulate plant-prey-predator interactions.

Conclusion: We conclude that timed LED regimes can be crucial in designing integrated pest management strategies that promote both plant growth and effective biological control in controlled environments. © 2025 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.