Evaluating how travel speed and target size influence the accuracy and precision of GPS-guided spray

Evaluating how travel speed and target size influence the accuracy and precision of GPS-guided sprayers in targeted pesticide applications

By Elisabeth Kitchin Graduate Student, Virginia Tech

Precision turfgrass management offers an exciting opportunity to apply resources such as pesticides, fertilizers, and water exactly where they are needed, reducing waste and optimizing turf health. Many modern sprayers are equipped with advanced features that can adjust spray patterns in real-time based on an uploaded map. These systems can shut off individual nozzles over areas that don’t require treatment, making them ideal for targeted pesticide applications. Previous research by Jordan Booth, Ph.D., showed that targeted fungicide applications for spring dead spot can maintain the same level of control as blanket fungicide applications while drastically reducing inputs. While the concept of site-specific pesticide application isn’t new, its practical implementation has been limited due to concerns about efficacy and precision. Additionally, there is still limited evidence showing how factors like travel speed and target size impact the precision and efficacy of these applications. This research project focuses on addressing these concerns by assessing how travel speed and target size influence the accuracy and precision of GPS-guided sprayers in targeted pesticide applications.

Figure 1: Data collection using UV lights and drone.

This study was conducted on a fairway at the Virginia Tech Golf Course in Blacksburg, VA. The trial area was divided into three rows, each sprayed at a different travel speed: 3 mph, 4.5 mph, or 6 mph. Within each row, circular targets of varying diameters (0.5 meters, 1 meter, and 2 meters) simulated turfgrass pest infestations of various sizes. Target locations were mapped, and each target’s center was marked with fluorescent orange paint to aid in post-application analysis. A Toro Multipro 5800G sprayer, equipped with GeoLink Precision Spray technology, was used to apply a UV fluorescent dye as a proxy for pesticides. This biodegradable dye allowed us to observe the exact spray deposition from the sprayer without compromising the health or appearance of the turfgrass. After spraying, UV lights were used to illuminate the trial area, and aerial images of sprayer deposition were captured using a drone. These images were analyzed to assess how much of the target area had been covered by the sprayer (accuracy), the distance between the target and the sprayer deposition, and the consistency of applications across replications (precision).

The results of the study showed great potential for the use of GPS sprayer technology in targeted pesticide applications:

• Accuracy and Precision: The sprayer applications were highly accurate, with nearly every target being hit and 70% of targets achieving 100% overlap accuracy, meaning the spray perfectly matched the intended target. This shows that GPS-guided sprayers can consistently deliver treatments to precise treatment maps.

• Target Size: Target size had no significant impact on the accuracy or precision of the applications. This means that GPSguided sprayers can effectively treat pests of varying sizes, from small spots of disease to larger weed infestations.

Figure 2: UV lights illuminating fluorescent dye deposition.

• Travel Speed: Speed was a critical factor in application success. Targets sprayed at 3 mph had lower accuracy and were further from the intended targets compared to speeds of 4.5 mph and 6 mph. This indicates that maintaining a travel speed of 4.5-6 mph is essential in order to achieve optimal application precision.

In conclusion, GPS-guided sprayers offer turfgrass managers a precise and sustainable way to manage pests while reducing pesticide use and minimizing environmental impact. As long as treatments are applied at appropriate travel speeds, these systems can treat pests of all sizes with high accuracy, providing effective management for turfgrass pests such as diseases and weed infestations. By addressing industry concerns about the efficacy of targeted applications, we hope to support the broader adoption of precision turfgrass pest management practices.