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Cover Story
Advances in Automated Spray Technology Can Lower Your Pesticide Costs
By Karl McKim, Extension Assistant, UT Department of Plant Sciences
Dave Lockwood, Extension Specialist and Professor, UT Department of Plant Sciences
Amy Fulcher, Extension Specialist and Professor, UT Department of Plant Sciences
Nursery producers are encouraged to use Integrated Pest Management (IPM) to prevent and control pests in their nurseries, ensuring that plants remain healthy and marketable. IPM programs utilize a combination of proactive measures, such as:
quarantining new plants
targeted scouting to detect pests early
selecting cultivars with insect and disease resistance
maintaining healthy plants through appropriate amounts of water and fertilizer
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Pests can refer to a variety of organisms, including insects that may infest and/or feed on the leaves, trunks, and roots of trees, as well as diseases caused by fungi, bacteria, or viruses that infect and damage plants.
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When pests do arise, spraying pesticides is a common practice. Pesticide application should be done in a targeted manner to avoid unnecessary input and labor costs as well as to avoid harming non-target insect and mite species, including those that provide control of pest insects.
Air-blast sprayers are the most common method of pesticide application in US nurseries. These sprayers propel pesticide solutions as a cloud into crops with strong airflows generated by a large fan, often indiscriminately. Air-blast sprayers equipped with the Smart Apply variable-rate intelligent spray control system use sensors and pulse width modulating (PWM) solenoids to control each nozzle’s output and deliver a more targeted and efficient pesticide application than conventional sprayers (Figure 1). The system works by detecting crops with a LiDAR sensor that communicates with an onboard computer. An algorithm uses information from this sensor and an onboard GPS to determine the appropriate spray output. Each nozzle is responsible for delivering this calculated volume to a designated zone of the crop. A nozzle does not spray when a target (plant) is not detected in its dedicated zone. This reduces both the total volume sprayed and the amount of spray delivered to unintended areas such as the space between trees.
The University of Tennessee tested this laserguided variable-rate technology at nurseries growing trees in multi-row blocks of field and pot-in-pot production systems, as well as apple orchards utilizing a range of training systems. In each trial the technology effectively controlled insect pests and diseases including several leaf spots and powdery mildew, a common fungal-borne disease in Tennessee nurseries, and several different types of leaf and fruit rots common to apple orchards (Figure 2). In research at six different nurseries and orchards, variable-rate technology consistently sprayed between 34% and 74% less pesticide than conventional air-blast sprayers. The technology also reduced the amount of spray landing in unintended areas within production blocks, as well as spray carried outside of blocks on wind, known as drift.
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Thinking about Buying Variable-Rate Technology? Here’s What You Should Know
Intelligent, variable-rate technology was conceptualized and developed by Dr. Heping Zhu and his team at USDA-ARS and tested for more than 15 years primarily by the University of Tennessee, The Ohio State University, and Oregon State University. The technology has been robustly tested especially for foliar applications, including in Tennessee nurseries and orchards. Variable-rate technology has proven to be as effective as conventional sprayers at controlling foliar pests while emitting a significantly lower spray volume, reducing a nursery’s environmental impact, and reducing chemical and labor costs.
Variable-rate technology is now commercially available at Smart-Apply, which is owned by John Deere. There is a one-time expense based on nozzle number and a yearly subscription. This technology has qualified for TAEP funding, although it is always best to verify a planned TAEP purchase before submitting your application.
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The reduced output results in economic savings for growers, who spend less on chemicals, water, fuel and labor to apply pesticides, while the reduced off-target applications limit the impact of pesticide spray on non-target organisms such as beneficial insects, and residue that workers contact after re-entry intervals have passed. Nurseries also benefit from increased productivity due to recouping worker time that was previously spent mixing pesticides and refilling the spray tank.
Ongoing research at the University of Tennessee is evaluating efficacy of using intelligent variable-rate technology to apply contact insecticides to tree trunks (Figure 3) and further potential for reductions in pesticide volume when spraying for foliar pests.
Laser-guided variable-rate spray technology is proven to reduce the volume of pesticide sprayed and enhances the efficiency of pesticide application versus conventional air-blast sprayers. Studies conducted at Tennessee nurseries and orchards have shown significant reductions in pesticide use, generally around 50%, and off-target ground loss, while still achieving comparable pest control. For detailed information on this technology, see UT Extension Publication W1280 “Using Smart Apply Variable-Rate Technology to Improve Air-Assisted Air-blast Sprayer Pesticide Application Efficiency in Nurseries and Orchard Crops”
https://utia.tennessee.edu/publications/wp-content/uploads/ sites/269/2024/09/W1280.pdf
Acknowledgments
The authors thank Blankenship Farms and Nursery, Hale and Hines Nursery, Oren Wooden’s Apple House, Pleasant Cove Nursery, The Apple Barn, University of Tennessee East Tennessee Research and Extension Center, and Walker Nursery for their partnership, Grace Pietsch and Wesley C. Wright for their invaluable research contributions, and USDA SCRI Grant # 2020-51181-32199 and USDA ARS SCA 58-5082-9-012, without which the research described in this article would not have been possible.
