Integrating visual stimuli in trapping protocols for longhorn beetles

Longhorn beetles (Coleoptera, Cerambycidae) are among the most significant groups of invasive forest insects worldwide. Hidden within live plants and wood-packaging materials, these beetles can escape routine inspections at entry points become major pests in the invaded environment. Traps baited with pheromones and kairomones and set up in and around entry points are commonly used to improve chances of intercepting exotic species soon after their arrival. Factors able to affect longhorn beetle catches in traps have been extensively studied in the last years. Whether visual cues can be used to further increase trap attractiveness is instead still unclear. In a trapping study carried out in 2023 at 4 forest sites in northern Italy, we investigated the response of four target longhorn beetle species and a number of non-target species to baited traps characterized by five different visual stimuli, that are: i) black color; ii) the color of the stripes/bands present on the target species elytra; iii) black color plus multiple reproductions of the color and pattern of the stripes/bands present on the beetle elytra; iv) black color plus multiple dots of the same color of the stripes/bands present on the beetle elytra; v) black color plus multiple pictures of the adult individual. Preliminary results clearly demonstrated a species-specific response of both the target and non-target longhorn beetles to the different visual stimuli, indicating that integrating them in baited traps can strongly improve trap efficacy.