###### Abstract  
Pest control is essential for increasing agricultural production. Agricultural drones with spraying systems for pest control have generated great interest among farmers. However, spraying systems installed on unmanned aerial vehicles, like any other sprayer, can cause damage to the environment due to drift of the agent. Air induction (AI) nozzles are known to produce less drift (e.g., larger spray drops) than other nozzles, but there is a lack of research analyzing their effectiveness in combination with drones. In this study, AI and flat fan nozzles were installed on drones to evaluate their spray and pest control performance. Aerial spraying was conducted on rice and soybeans to measure the coverage and penetration ratio and analyze the crop production as well as the crop damage due to pests and diseases. The drone flight was conducted at an altitude of 3 m and a velocity of 2 m/s. Spray droplets were collected using water-sensitive paper at two heights above the soil surface. The experiments showed that the crop coverage with the AI nozzle was 130% higher than that with the flat fan nozzle. The drift reduction of AI nozzles increased the coverage of spray droplets. But the difference in the penetration ratios, which is the ratio of agents to be delivered inside the crop, was not significant between the nozzles. Also, there was no significant difference in crop yield and pest control efficacy. Consequently, the performance of the AI nozzle did not show differences from that of the XR nozzle, except for coverage. However, the AI nozzle raised less drift, so it should be considered for use in aerial control. agricultural drones; air induction nozzle; aerial spraying; control efficacy; coverage; penetration ratio +
Footnote †: journal: Medical  
from the rotor. Agricultural drones facilitate convenient operations, high work efficiency for targeted application, and high worker safety; therefore, their use by farmers is gradually increasing [13; 14; 15]. In particular, agricultural drones are widely used in East Asia [16]. For example, China has 106,000 drones for pest control, and their work area is estimated to be 64 million hectares [17]. [PERSON] et al. [18] analyzed the current pest control status using drones in China, Japan, and South Korea and presented the challenges of aerial spraying. In Europe, a few studies of spray drones in mountainous terrain have been conducted in spite of regulation [19]. Several studies focused on improving the usability of agricultural drones have been also conducted [20; 21]. With the growth of the agricultural spraying drone market, there is a huge concern about the drift of pesticides and drop bounce from agricultural drone spray systems [22]. In Europe, aerial spraying is generally not permitted due to the risk of drifts [23]. In South Korea, aerial spraying has also become a problem due to revised pesticide use standards in 2019. The quantity of drift is generally associated with the ratio of fine spray droplets [24]. Depending on the size of the spray droplets, more than 70% of the volume can be drifted [25]. Many factors including flight altitude, additives, and downwash can affect the spraying performance of agricultural drones [26; 27; 28]. Various studies have been conducted to analyze droplet downwash from drones [29]. [PERSON] et al. [30] conducted a study to build a CFD model to analyze the effects of downwinds and crosswinds on the behavior of sprayed droplets. [PERSON] et al. [31] researched influence of the downwash airflow of UAVs and found that the strength of the airflow is positively correlated with deposition and penetration and negatively correlated with uniformity and drift. The type of nozzle determines the diameter of the sprayed droplets and the spray angle and shape, thereby substantially impacting spraying performance [32; 33]. [PERSON] et al. [25] used four flat fan nozzles with different orifice sizes to analyze the effect of droplet size on droplet deposition and drift.