Intelligent, variable-rate spray technology reduces total pesticide output while controlling foliar disease of Shumard oak

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

Submitted to: Journal of Environmental Horticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/30/2023
Publication Date: 10/5/2023
Citation: Fessler, L., Xiaocun, S., Wright, W.C., Zhu, H., Fulcher, A. 2023. Intelligent, variable-rate spray technology reduces total pesticide output while controlling foliar disease of Shumard oak. Journal of Environmental Horticulture. 41(3):109-120. https://doi.org/10.24266/0738-2898-41.3.109.
DOI: https://doi.org/10.24266/0738-2898-41.3.109

Interpretive Summary: Field tests have consistently demonstrated that the laser-guided intelligent variable-rate spray technology can significantly reduce pesticide consumption and off-target waste when it is retrofitted onto sprayers commonly used in commercial nurseries. However, pest control with this new technology for different nursery production systems must be sufficiently investigated to give growers confidence in its adoption. In this research, effectiveness of the intelligent variable-rate spray technology retrofitted on an air-assisted sprayer was tested in a commercial nursery with multiple-row pot-in-pot production systems. It was also compared with the same sprayer practicing conventional constant-rate applications. Test results showed that the intelligent spray application could control two fungal borne diseases equally or better than the conventional spray application while reducing the spray volume by 43%. Additionally, this study discovered substantial spray deposits on the container potting surface with both intelligent and conventional applications, which could be helpful to maintain healthy substrate and tree roots for the pot-in-pot production systems. Thus, the large reduction in pesticide use and the effective disease control with the intelligent spray technology can not only decrease annual input costs for growers but also mitigate potential chemical risks to human and environmental health.

Technical Abstract: Air-blast sprayers have known inefficiencies in nursery production systems. Intelligent, variable-rate spray technology aims to improve application accuracy and reduce total pesticide consumption by utilizing pulse-width modulated solenoid valves, laser scanning and ground speed sensors, and a computerized algorithm to customize spray output based on plant presence, size, shape, and density. This study used an air-blast sprayer retrofitted with this variable-rate spray technology to directly compare spray characteristics and pest control of the sprayer operated in intelligent, variable-rate mode and conventional, constant-rate mode to spray 57-L (15-gal) trees in a multi-row pot-in-pot production system. Variable-rate mode reduced total spray volume by 43% while providing equivalent, and at times better, disease control compared to the constant-rate mode for two fungal borne diseases of Shumard oak (Quercus shumardii Buckley). This research demonstrates the capability of variable-rate technology to reduce input costs, environmental harm, and risk of pesticide exposure while simultaneously controlling disease and maintaining saleable crops.