Effects of Nozzle Types and Spraying Volume on the Control of Hypera postica Gyllenhal by Using An Unmanned Aerial Vehicle

In the current study, an unmanned aerial vehicle (UAV) was selected for agricultural spraying, with two nozzles, two insecticides and three spraying volumes as the spraying variables; this paper explores the impact of spraying volume on the droplet deposition in alfalfa fields. Furthermore, by comparing the control effect of spraying insecticides on alfalfa leaf weevils and the safety of pasture by UAV, the aim is to establish efficient pesticide spraying techniques for pest control in alfalfa fields, providing guidance for the green control of alfalfa leaf weevils. The effective droplet proportion of the fan-shaped nozzle (SX11001VS) was higher than that of the hollow conical nozzle (TX-VK4), and increasing the spraying volume cannot significantly improve that situation. When the spraying volume increased from 22.5 L/ha to 45.0 L/ha, the average droplet coverage, density and deposition of the two types of nozzles increased with the spraying volume. However, when the spraying volume was 30.0 L/ha and 45.0 L/ha, the average deposition of the two types of nozzles was similar. The control effect of chlorantraniliprole on alfalfa leaf weevils sprayed by using a UAV was higher than that of spinosad. There was a positive correlation between the spraying volume and the control effect, and the prevention effect of the hollow conical nozzle was better than that of the fan-shaped nozzle. The residues of chlorantraniliprole in alfalfa plants after spraying increased with the spraying volume, whether a fan-shaped nozzle or a hollow conical nozzle was used.