Visual modelling can optimise the appearance and capture efficiency of sticky traps used to manage insect pests

Abstract

Sticky traps are one of the most important tools for monitoring and mass trapping of insect pests. Their effectiveness depends on attracting and capturing target pests efficiently. Trap colour strongly affects capture rates, but currently a principled approach to identifying optimal trap colour for a given pest and growing context is lacking. Here we propose that modelling pest colour vision enables identification of trap colours that optimise pest capture rates. We test this novel approach to trap design in field trials on Western flower thrips (WFT) Frankiniella occidentalis, an economically damaging pest of agriculture and horticulture worldwide. Prior studies have reported that WFT prefer blue and yellow sticky traps, aligning with recent evidence that WFT have trichromatic colour vision with peak sensitivities in the UV, blue and green portion of the visual spectrum and a blue-green colour opponent mechanism. Therefore, we hypothesised that a shade of blue that maximally stimulates the blue photoreceptor whilst minimally stimulating the green photoreceptor would improve sticky trap capture rates, while a shade of blue that decreased the opponent response would reduce capture rates. In three field experiments, we found strong support for this hypothesis: the optimised blue colour captured 1.3–2.6 times more WFT than current commercial trap colours. Our results also demonstrated that visual modelling can identify optimally contrasting colours for two-colour traps that further improve capture rates. This study provides a novel and principled approach to the design of visual traps that could be extended to other pest management contexts.

Colour shade and chemical influences on the capture of adults Frankliniella occidentalis (Thysanoptera: Thripidae) in blackberry crops

“…This supports the hypothesis that attractiveness will be optimized when blue colours maximally stimulate blue photoreceptors while minimally stimulating green photoreceptors (Dearden et al, 2023).…”

“…Colour contrast also plays a crucial role in the localization and identification of suitable hosts for numerous fruit-eating and frugivorous insects (Burns & Dalen, 2002;Schaefer et al, 2006;Schmidt et al, 2004;Teixeira et al, 2010). Encouraging results have been observed when assessing visual stimuli in contrast to the background colour for WFT attraction (Dearden et al, 2023;Mainali & Lim, 2010;. It has also been reported that adding 200-400 μg of neryl (S)-2-methylbutanoate (aggregation pheromone) to blue and yellow traps increased capture rates by 2.5-3 times compared to the same traps without bait (Cruz-Esteban et al, 2020).…”

Attraction of Frankliniella occidentalis Females towards the Aggregation Pheromone Neryl (S)-2-Methylbutanoate and Kairomones in a Y-Olfactometer

“…In one experiment conducted in England, traps baited with ( S )-(-)-verbenone significantly caught more thrips than traps baited with the solvent, whereas, in a second experiment conducted in Turkey, the results of the same odor treatment could be hardly distinguished from the solvent control [ 45 ]. Recently, a commercial lure, namely Thrips Charm ® , a mixture of p -anisaldehyde and ( S )-(-)-verbenone significantly increased catches from visual traps in the field [ 46 ]. No details about the ratio of both compounds in the commercial lure could be found.…”