Spectral discrimination by Synanthedon myopaeformis (Lepidoptera: Sesiidae) when orienting to traps baited with sex pheromone or feeding attractants

Abstract

AbstractApple clearwing moth, Synanthedon myopaeformis (Borkhausen) (Lepidoptera: Sesiidae), is an invasive species in Canada and a destructive pest of commercial apple trees in British Columbia. Adult mass trapping is being developed to help organic apple producers manage this pest. We manipulated and measured spectral reflectance from delta traps, unitraps, and bottle traps used to deploy sex pheromone, phenylacetaldehyde, and grape juice mass-trapping baits and compared catches in baited traps having different reflectance properties. Synanthedon myopaeformis did not discriminate among pheromone-baited delta traps painted yellow, green, or white, from those left clear (group 1), nor among those painted purple, blue, red, or black (group 2). Catches by all treatments in group 1 were significantly greater than all in group 2. Catches in pheromone-baited delta traps were positively correlated with their intensity of green wavelength reflectance (500–550 nm). Fluorescent yellow delta traps reflected more green and ultraviolet (300–400 nm) light than standard yellow or green traps but caught significantly fewer moths when baited with pheromone, implying an antagonistic interaction of green versus ultraviolet-sensitive behaviours. Pheromone-baited all-yellow unitraps caught significantly more moths than equivalent all-green, all-white, or all-red unitraps. Catches in pheromone-baited all-yellow unitraps decreased when any component (lid, funnel, or bucket) was replaced with a green one. Changing the intensity or quality of reflectance from funnels had the greatest impact on unitrap catches (82% reduction). Spectral preferences were modulated by odours eliciting different behaviours (mating versus feeding). When baited with the floral feeding odour phenylacetaldehyde, yellow and green delta traps were among the least attractive, whereas black and blue traps were among the most attractive. When baited with grape juice food baits, black bottle traps caught significantly more moths than any other colour except white, and the former are recommended for maximising mass trapping of females while minimising nontarget impacts of juice baits.