Scotophase interruption with LEDs and OLEDs to inhibit photoperiodic induction of diapause in Tetranychus urticae and T. kanzawai (Acari: Tetranychidae)

Abstract

Tetranychus urticae Koch and T. kanzawai Kishida enter facultative diapause in response to short-day photoperiods. To determine the effect of various colors of light-emitting diodes (LEDs) and organic light-emitting diodes (OLEDs) on diapause induction, both species were reared under different photoperiods at 18°C and 2.0 W m -2 light intensity, in which photon flux density (PFD) was 7.9–11.0 µmol m −2 s −1 depending on light quality. Under blue, green, and white LEDs, critical photoperiods were ca. 13.5:10.5 h L: D for T. urticae and ca. 12.5: 11.5 h L: D for T. kanzawai , but no diapause was induced in either species under red LEDs. Under blue, green, orange, and white OLEDs, the critical light phases were ca. 13.3–13.5 h for T. urticae and ca. 12.5 h for T. kanzawai . The inhibitory effects of the duration, quality, and intensity of scotophase-interrupting lights on diapause induction in both species were tested under an 8:16 h L: D photoperiod. In T. urticae females, diapause induction was prevented by interrupting the scotophase with 1 h of light from all colors of LEDs or OLEDs except red LEDs. However, in T. kanzawai females, diapause was fully induced with 1-h scotophase interruption of all light colors and types, even when the PFD was as high as 20 µmol m −2 s −1 . Interrupting the scotophase with 3 h of 20 µmol m −2 s −1 light from blue, green, and white LEDs, and from blue, green, orange, and white OLEDs completely inhibited diapause induction in both species. When interrupting the dark phase with 3 h of light at the lowest intensity tested (0.2 µmol m −2 s −1 ), blue and green inhibited diapause induction in T. urticae , whereas only blue light inhibited diapause induction in T. kanzawai . Therefore, blue LED and OLED performed best to inhibit diapause of T. urticae and T. kanzawai at 3-h scotophase interruption even at low light intensity.