Light beams from lasers or reflective devices are intended to disturb wildlife, and make vision uncomfortable and thereby deter them from agricultural crops.
In New Zealand, Fukuda et al. (2008) tested the Peaceful Pyramid, a mirror pyramid which is rotating and reflecting light beams towards the sky. In the trials to deter bird damage on grapes, no effect was observed between treatment and control plots, where the damage levels were overall high (RR = 1.01).
In Rhode Island, USA, a portable, battery-powered robotic scarecrow was designed to continuously move a 14 mm diameter, 532 nm wavelength beam from a 50 mW laser to reduce damage from European starlings and red-winged blackbirds to sweet corn (Brown and Brown 2021). During three subsequent years, lower proportions of damage were observed in treatment plots than in control plots, but the relative risk increased over time in response to reduced damage in control plots (year 1 RR = 0.30, year 2 RR = 0.58, year 3 RR = 0.73). Clausen et al. (2019) used hand-held lasers (Agrilaser 500) to displace grazing barnacle geese (Branta leucopsis) and brent geese (Branta bernicla bernicla) from farmland pastures in Denmark. In treatment plots, grass sword height was 87 % greater than in controls.
In Nebraska, USA, Gilsdorf et al (2004) evaluated the electronic guard with a photocell, timer, flashing white strobe light (70,000 cp, flash rate=60/minute), and a 1.4-kHz modulating siren (15–20 modulations/minute, 116-dB output at 1 m), for its effect in reducing damage from white-tailed deer (Odicoileus virginianus) on corn. Only a 5 % difference in yield was observed between treatment and control fields, leading to the conclusion that the intervention was ineffective.
