Diel and Circadian Patterns of Locomotor Activity in the Adults of Diamondback Moth (Plutella xylostella)

SIMPLE SUMMARY: Plutella xylostell is a worldwide migratory insect pest that mainly damages cruciferous vegetables. In this study, we established a system for measuring the diel locomotor activities and used it to evaluate the locomotor circadian patterns of P. xylostella. We tested the locomotor activities of P. xylostella adults under several laboratory settings. We found that both the males and females showed nocturnal activity under a light:dark (LD) cycle, with activity peaking very early after lights off and quickly declining after lights on. Both males and females had high locomotor activity levels in constant darkness (DD) but weak in a constant light condition (LL). In addition, circadian patterns analysis showed that males exhibit much better rhythmic characteristics than females, especially in low temperature conditions. Overall, our proposed system for studying the locomotor activities in P. xylostella is reliable, which will help us to have a better understanding of the diel activity of P. xylostella and may finally be helpful in the development of an effective pest management strategy. ABSTRACT: The Diamondback Moth (Plutella xylostella) is a highly destructive lepidopteran pest of cruciferous crops. However, there still is relatively little known about the locomotor activities of diel and the circadian patterns in P. xylostella. Here, we present an analysis of the diel locomotion of P. xylostella under several laboratory settings. We established a system for measuring the individual locomotor activities of P. xylostella and found that both males and females showed a nocturnal pattern of activity under 26 or 20 °C LD conditions, with activity peaking immediately after lights off and quickly declining after lights on. In addition, we showed that it is difficult to assess the free-running circadian rhythms of P. xylostella under 26 °C DD conditions. However, we found that males showed a higher power, rhythm index (RI) and rhythmic ratio than females under 20 °C DD conditions, which indicated that males in low-temperature conditions are much more suitable to study the free-running circadian rhythms of P. xylostella. The findings of this study will help us to have a better understanding of the diel activity of P. xylostella and may provide a foundation for the development of an effective pest management strategy.