Use of unmanned aerial vehicles for application of low-risk insecticides to control Japanese maple scale, 2023 Open Access

The weeping Japanese maple trees used in our experiment were field-grown and about 1.5–2 m tall and 1 m wide. The soil was clay loam with a pH between 6.0 and 6.5. These trees were naturally infested and sustained a high population of L. japonica scale. Treatments were assigned to individual trees under a RCB design with 6 replicates. Buffer trees were left untreated between sprayed trees. The treatments were drone applications of 2 insecticides, Mainspring GNL (cyantraniliprole), Talus 70DF (buprofezin), and an untreated control. Treatment applications were made on 26 June 2023 using a DJI 30 Drone, manufactured by DJI (https://www.dji.com/), with 3.16 L applied per each tree. A pre-treatment evaluation conducted on 26 June 2023 by sampling a 15–20 cm section of 4 ordinal branches per tree confirmed the presence of scale. On this date, all branches were infested with JMS, and at an average of 96 live scales per branch section. Before treatment, 4 ordinal branches per tree were tagged and had live scale on their basal portions but none on the ends. Flagging tape was used to mark the limit of the branch scale infestation. No live scales were observed to be present past the flagging tape. Treatment effects were evaluated on 4 Jan 2024 after natural defoliation when scales are visible on the infested trees. The 4 previously flagged branch sections on each tree, identified as clean on the pre-treatment date, were again checked visually for first- and second-instar settled stages. Post-treatment insect counts were made on 4 Jan 2024 using a 16× hand lens. Japanese maple scale numbers from individual branches were summed for each tree prior to analyses. Analysis was made using a generalized linear model with a Poisson error distribution. Insecticide treatment had a significant effect on scale abundance.

Pairwise means comparisons using Tukey’s HSD showed that Mainspring and Talus treatments significantly reduced scale abundance relative to the untreated check but were not significantly different from one another (Table 1). Mainspring reduced scale abundance by 98.6% relative to the control, while Talus reduced scale abundance by 98.8%.¹

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