Visual cues may be important for attracting wildlife to crop seeds and fruits, and disruption with other colours could then repel consumption of crops.
A preliminary study from France (Destrez et al. 2022) used blue colour on sunflower seeds to deter carrion crows (Corvus corone) from feeding on the seeds. Colouration appeared to reduce the risk of seed predation (RR = 0.43) over the four-hour trial. Mitchell and Bruggers (1985) evaluated a white compound (CaCO3) and a blue compound (Carpenter's chalk) to repel Hispaniolan woodpecker (Melanerpes striatus) from damaging cacao pods in Dominician Republic. Damage reductions occurred in both treatment and control, and the relative risk was thereby not reduced by neither white (RR = 1.29) nor blue (RR = 1.8) compounds.
