Attenuation of ultraviolet (UV) radiation does not impede host location in egg parasitoids with positive UV phototaxis

Abstract

Abstract In insects and other terrestrial arthropods, foraging is guided in part by visual cues making use of optical radiation, which includes ultraviolet (UV) radiation. Manipulating UV exposure with lamps and photo‐selective materials can help protect crops by disrupting related wavelength‐dependent behaviours in various pests, but little is known on how this could also affect the behaviour of their natural enemies. To investigate the effects of UV‐A radiation on parasitoid wasp foraging behaviours, we conducted laboratory and semi‐field experiments on female Telenomus podisi and Trissolcus utahensis (Hymenoptera: Scelionidae) that parasitize stink bug egg masses. In small laboratory arenas, both species of egg parasitoid displayed a positive UV phototaxis, but UV exposure also reduced their daily spontaneous locomotor activity regardless of the time of day. In large field cages, parasitism (i.e., host discovery and exploitation) rates were mostly unaffected by UV‐attenuated conditions created by UV‐absorbing filters (macrohabitat level) and/or by the plant canopy (microhabitat level). This study indicates that UV radiation can be involved in egg parasitoid foraging behaviours without UV attenuation negatively affecting parasitism, reflecting the heterogeneity and potentially hazardous nature of this abiotic factor. We highlight the importance of examining the role of UV radiation as an environmental cue in beneficial insects, especially with the prospect of combining physical and biological pest management strategies.