Matthew Milburn, Agriculture Program Associate, Rutgers Cooperative Extension of Middlesex County, matthew.milburn@rutgers.edu
David Hlubik, County Agent III, Rutgers Cooperative Extension of Burlington County
Introduction
Among small fruit growers, blueberry producers often experience the highest levels of yield loss due to avian damage. [1] Many of the deterrents available to growers are often cost-prohibitive, not suitable for use in areas with nearby residences, or are overcome through habituation. One emerging technology that has shown promise to bypassing these issues while reducing bird damage is the University of Rhode Island Vegetable Program’s (URI) Laser Scarecrow. [2] The URI Laser Scarecrow is an experimental unit, designed specifically with small to medium-scale growers in mind. The laser system is currently available at cost to growers who are willing to work with and contribute to the URI Program Team’s research efforts. To test the potential efficacy of the URI Laser Scarecrow on blueberries, two adjacent field trials were conducted at the Rutgers Philip E. Marucci Center for Blueberry and Cranberry Research and Extension in Chatsworth, NJ.
Materials and Methodology
For this study, the URI Laser Scarecrow model utilized was the 2025 Berry Prototype. This unit consisted of two 532nm, 50mW laser modules mounted on a rotating arm assembly (Figure1). Features such as laser pathing, rotational speed, and time of operation were all programmable. Safety considerations, including proper signage and eyewear protection, were employed based on the URI Laser Scarecrow Operating Manual and the Rutgers Environmental Health & Safety staff recommendations.
Two adjacent blueberry fields were utilized during the spring and summer of 2025. Fields 1 and 2 were approximately 0.8 acres and 1.25 acres, respectively. Field 1 was in its sixth year of production and was planted with the northern highbush variety ‘Duke’, while Field 2 was in its fourth year and was planted with the variety ‘Draper.’ Neither field received supplemental irrigation nor were harvested fully on a regular basis. A split-block design for each field was implemented, with half the field being treated with laser coverage and the remainder serving as an untreated control (Figure 2). To uncover any differences in feeding due to location, blocks were further divided into an inner and outer stratum. Both fields were noted for experiencing high levels of bird damage in the past, likely due to their location between a woodland border and an irrigation canal, making an ideal habitat for supporting bird populations.
Based on previously established protocols [3], individual branches were randomly selected and marked across both fields. Exterior stratums were allocated 24 replicates per block, while the interior stratums had 12. Due to the loss of a few plants prior to the end of the harvest season, the total replicates for Fields 1 and 2 ended up being 70 and 71, respectively. Initial berry counts were taken around the green fruit stage of development, BBCH microstages 78-81 [4], on June 13th and 16th. Once fruit had begun to ripen, four weekly harvest events were conducted between June17th and July 11th. Berry loss percentages per replicate were calculated by comparing total fruit harvest data to initial berry counts, providing an estimate of bird damage (Figure 3).
Results
The two bird species predominantly observed within the field trials were red-winged blackbirds (Agelaius phoeniceus) and brown-headed cowbirds (Molothrus ater.) Larger flocking bird species that were commonly found in the area, such as Canada geese (Branta canadensis) and a variety of gull species, were rarely observed in the laser-treated field areas.
Across both fields, harvest data indicated reduced berry loss in laser-covered blocks when compared to the control blocks. For Field 1, the laser-covered block experienced 9.10% yield loss, while the control was 18.40%, while Field 2 experienced losses of 19.38% and 25.01%, respectively (Figure 3). Using a three-way ANOVA, the effect of the field location was found to be significant, with a p-value of 0.02 (Figure 4). More importantly, the treatment effect was found to be significant as well, with a p-value of 0.04. There were no significant differences in bird damage between the interior and exterior stratums, and no significant interaction effects among the treatments were observed.
Conclusion
During this study, the use of the URI Laser Scarecrow appeared to be an effective measure for reducing bird damage in blueberries. One major limitation of the study was due to the fields’ infrequent harvesting which would not be comparable to a commercial setting but may relate more with a Pick-Your-Own (PYO) operation. To further validate these initial findings, additional field trials across diverse environments are warranted. If differences in bird damage can be quantified, efficacy field trials on small farm operations, such as PYO’s, should be explored as well. Other crops of interest heavily impacted by bird damage, such as wine grapes, should also be explored as candidates for future laser deterrent efficacy trials.
Acknowledgements
We gratefully acknowledge the New Jersey State Horticultural Society, whose grant allowed us to purchase the two laser module units used in this study. We also thank Dr. Peter Oudemans, Director of the P. E. Marucci Center for Blueberry and Cranberry Research and Extension, along with technicians Matthew Hamilton and Wesley Bouchelle, for facilitating our research efforts this past spring. Special thanks to Dr. Rebecca Brown and the URI Laser Scarecrow Project Team at the University of Rhode Island for providing discounted laser modules and technical support. For more information about the URI Laser Scarecrow Project, visit www.laserscarecrow.info.
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[2] S. T. Manz, K. E. Sieving, R. N. Brown, P. E. Klug and B. M. Kluever, "Experimental assessment of laser scarecrows for reducing avian damage to sweet corn," Pest Management Science, vol. 80, no. 3, pp. 1547-1556, 2023.
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[4] F. K. J. J. S. B. A. W. Merret Anna Wichura, "Phenological growth stages of highbush blueberries (Vaccinium spp.): codification and description according to the BBCH scale," Botany, vol. 102, no. 11, 2024.
