Can a LiDAR-enhanced Air-blast Sprayer Improve Coverage on Tough Targets like Tree Trunks and Emerging Shoots?

Abstract

Eastern filbert blight (EFB) and pacific flatheaded borer (PFB) are two problems of Pacific Northwest orchard and nursery production. Fungicides and insecticides used to manage these issues are typically applied to plant tissues with minimal foliage present that can result in considerable spray waste or drift. The Intelligent Spray System (ISS) is a laser-guided, variable-rate sprayer that detects objects in the target zone and releases spray volumes proportional to the density of plant tissues, thereby increasing application efficiency and reducing waste. However, the ISS has not been tested when targeting low-foliage plant tissues such as emerging shoots and trunks. Three experiments were conducted from 2018 to 2021 to evaluate the potential use of the ISS for EFB and PFB management by assessing spray coverage on emerging hazelnut shoot tips, hazelnut tree trunks, and maple tree trunks. On hazelnut shoot tips, coverage was <10% of the shoot on both adaxial and abaxial sides, with the highest coverage on the adaxial side (9.5%) resulting from spraying in standard mode (no sensors) at 3.1 kph. On hazelnut trunks, application at the slowest tested speed (3.1 kph) in intelligent mode resulted in spray coverage greater than or equal to that applied in standard mode at 5.1 kph. In addition, coverage was significantly higher on cards placed on the ground between trees when the sprayer was used in standard mode, indicating higher amounts of wasted spray and drift over intelligent mode. On maple trunks, the slowest speed tested (3.1 kph) resulted in the highest coverage of tree trunks facing the sprayer that were two and three rows away from the sprayer, with the highest coverage levels on the row of trees closest to the sprayer occurring at the highest tested speed of 6.4 kph. On cards placed on trunk sides not facing the sprayer, the slowest tested speed of 3.2 kph resulted in significantly higher coverage than both treatments at 6.4 kph and intelligent mode at 4.8 kph in the tree row closest to the sprayer. This work has demonstrated a baseline of coverage that hazelnut buds receive when spraying for EFB, illustrates that the ISS was able to effectively target trunks, and could be an alternative to drenches for PFB control.