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Improving UAV effectiveness for spot application of Btk during incursion responses

Unmanned aerial vehicle (UAV) platforms are proliferating throughout the world. One identified UAV niche is applying plant protection products to discrete tall trees situated in sensitive areas such as urban environments.


The use of UAVs for treating individual tall trees infested with unwanted insects or pathogens has potential advantages over other spray delivery technologies such as helicopters for this type of operation. UAVs may deliver spray applications with increased efficiency and efficacy through improved on-target deposition and reduced unwanted environmental impacts and risks to the public.


This project was designed to simulate an incursion response and quantify the efficiency of spray delivery from a UAV to a tall tree . An aligned project considered social and cultural perspectives of UAV operations with a view to co-designing acceptable practice.


Previous B3 research to quantify UAV-applied spray deposition throughout the canopy of a tall tree showed that the typical aerially applied lepidopteran bio-insecticide spray application, neat Foray48B with fine ~125 µm volume median diameter (VMD) droplets at low ~5 L.ha-1 rate, is at high risk of wind induced spray displacement and drift. Even wind speeds >1.5 m.s-1 (light breeze on the Beaufort scale) at the point of release, ~17m above ground level, will cause significant spray displacement of this standard treatment from a UAV reducing targeting accuracy and risking contamination of neighbouring properties.


This current study investigated a lower drift-risk application method using 7.25% diluted Foray48B and medium ~300 µm VMD droplets applied at 69 L.ha-1. This treatment should deliver the same dose and number of droplets per unit foliage area as the standard treatment.


It was found the diluted and neat Foray48B formulations had similar surface tension and wetting (contact angle on easyand hard-to-wet surfaces) properties which indicate similar spray adhesion and retention would be expected.


A bespoke UAV with micromiser nozzles was used to apply each treatment to a 15m tall Gingko tree. Preliminary results suggest the low drift application provided similar penetration and coverage to the standard treatment, under ideal wind conditions which would not compromise the targeting accuracy through wind displacement or drift.


Evaluating any effects of the diluted product on efficacy against a target insect requires separate evaluation.


Contact Project Leader Justin Nairn [email protected]