Reducing the nursery pesticide footprint with laser-guided, variable-rate spray application technology

Authors: FESSLER, L - University Of Tennessee; FULCHER, A - University Of Tennessee; SCHNEIDER, L - University Of Tennessee; WRIGHT, W - University Of Tennessee; Zhu, Heping

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/20/2021
Publication Date: 12/10/2021
Citation: Fessler, L., Fulcher, A., Schneider, L., Wright, W.C., Zhu, H. 2021. Reducing the nursery pesticide footprint with laser-guided, variable-rate spray application technology. HortScience. 56(12):1572-1584. https://doi.org/10.21273/HORTSCI16157-21.
DOI: https://doi.org/10.21273/HORTSCI16157-21

Interpretive Summary: While pesticides are essential for pest management and save approximately $40 billion worth of crops each year in the U.S., it is estimated that the environmental cost of pesticides approaches $10 billion. Nursery operators face a number of unique challenges when it comes to pesticide application due to lack of crop uniformity in shapes, sizes, growth patterns, and harvest schedules. To overcome these changes, the laser-guided variable-rate intelligent spray technology was developed and commercialized. In this research, the use of this intelligent spray technology was validated in a commercial nursery in Tennessee. Tests were conducted to compare control of a pervasive disease on a highly susceptible host, spray volume, and spray application characteristics of the intelligent sprayer with those of a conventional air-blast sprayer. Under the southern climate conditions, powdery mildew, a ubiquitous and costly disease for dogwood producers, was controlled effectively in the commercial nursery planted in multi-row blocks by both sprayer types throughout the course of two seasons. However, when compared to an already reduced conventional constant-rate application of 187 liter per hectare, the intelligent sprayer reduced spray volume by more than 50% while successfully achieving effective disease control. Thus, the intelligent technology reduced total pesticide use, not only dramatically reducing input costs for growers but also lowering the environmental impact to soil, water, air, and non-target organisms, as well as reducing worker exposure to chemicals.

Technical Abstract: Nursery producers are challenged with growing a wide range of species with little to no detectable damage from insects or diseases. Growing plants that meet consumer demand for aesthetics has traditionally meant routine pesticide application by the most time-efficient method possible, an air-blast sprayer, in spite of known poor pesticide application efficiency. New variable-rate spray technology allows growers to make more targeted applications and reduce off-target pesticide loss. In this research, a prototype laser-guided variable-rate sprayer was compared to a traditional air-blast sprayer. Pesticide volume, spray application characteristics, and control of powdery mildew were evaluated over two growing seasons. Spray application characteristics were assessed using water sensitive cards (WSCs) and DepositScan software. This prototype sprayer reduced pesticide volume by an average of 54% across both years despite being tested against a low rate, below 250 L'ha-1. In 2016, the conventional sprayer had more than double the deposit density on target WSCs among distal trees than the variable-rate sprayer; however, within proximal trees there was no difference between the two sprayer types. In 2017 when the trees were larger, within both the distal and proximal trees, the conventional sprayer had greater deposit density on target WSCs than the variable-rate sprayer. In 2016, coverage on target WSCs was nearly 7-fold greater in the conventional treatment than the variable-rate treatment. In 2017, when trees were larger, there was greater coverage on target WSCs in proximal trees (3.8%) compared to distal trees (1.0%) regardless of sprayer type. This variable-rate spray technology provided acceptable control of powdery mildew severity on individual branch and whole tree ratings and maintained incidence of powdery mildew to levels comparable to that occurring among trees sprayed with a traditional air-blast sprayer. Therefore, the variable-rate spray technology has the potential to effectively control disease, dramatically reduce the pesticide footprint, and preserve natural resources such as ground and surface water, soil, and beneficial insects found within and around nurseries.