Research progress on spray drift of droplets of plant protection machainery

More than 80% of pesticide formulations are used in plant protection by spraying in China. The spraying drift, including wind drift and evaporation drift, caused by the spraying liquid from the nozzle to the target crop is one of the important factors that pesticides cause human and animal health risks and ecological damage. With the pesticide application technology system shifting from grounded-based application to ground-based and aviation application in China, spray drift has become the focus and hot spot of application technology research. In order to better understand the spray drift, including spray droplets (size distribution, viscosity, surface tension, vapor pressure, volatility, density, etc.), spray pattern(nozzle type, spray speed and height, spray method) and external conditions(wind speed, wind direction, temperature, humidity, airflow and operator technical level, etc.) are systematically analyzed in this article. Meanwhile, the advantages and shortcomings of spray drift determination methods like field tests, indoor tests, computer simulation and new testing techniques are reviewed in detail, and proposed that the study of spray drift for plant protection unmanned aerial vehicle should be carried out combining indoor determination, field tests and computer simulation together. Furthermore, the risk control techniques of spray drift are analyzed and summarized, which are directly controlled by changing the movement mode and physicochemical properties of spray droplets and indirectly controlled by field layout.