P20 plant protection UAV to control cnaphalocrocis medinalis by reduced pesticide application

Plant protection Unmanned Aerial Vehicles (UAV) have widely been applied for rice diseases and pest control in China. This study aims to promote the reduced application of pesticides in rice, thereby exploring the control efficacy of pests and diseases using plant protection UAV. A field experiment was also conducted using a P20 quad-rotor plant protection UAV with a centrifugal spray system at the late tillering and booting stage of rice. A droplet deposition experiment of rice canopy was performed on two spray volume levels of 15 and 22.5 L/hm2. Three levels of pesticide dosage were determined to be 480, 540, and 600 mL/hm2 (80%, 90%, and 100% of recommended dosage) for the cnaphalocrocis medinalis control efficacy with the same two spray volume levels (15, and 22.5 L/hm2). Meanwhile, a pesticide spraying test was conducted with a knapsack electric sprayer (KES) for comparison as well. The droplet deposition test showed that the droplet was evenly distributed in the upper-canopy, better than that in the lower-canopy. There was an extreme difference in the droplet deposition on the upper- and lower-canopy of rice at the same spray period and spray volume. In particular, the droplet deposition on the upper-canopy was much larger than that on the lower-canopy. There were also significant differences among the droplet deposition on the upper-canopy between 15 and 22.5 L/hm2. Compared with that of 15 L/hm2, the spray volume of 22.5 L/hm2 increased the droplet deposition on the upper-canopy by 64.77%, and 60.53% at the late tillering and booting stage, respectively. Nevertheless, there was no significant difference among the droplet deposition of upper- and lower-canopy between the late tillering and the booting stage. The control efficacy test showed that the pesticide dosage presented a great effect on the control efficacy of cnaphalocrocis medinalis, indicating that the larger pesticide dosage achieved better, where the control efficacy of 100% pesticide dosage was the best. Specifically, the control efficacy of plant protection UAV was better than that of KES at the same pesticide dosage. There was a significant difference in the control efficacy between the spray volume of 15 and 22.5 L/hm2. The control efficacy at the late tillering and booting stage with 22.5 L/hm2 increased by 21.51% and 7%, respectively, compared with 15 L/hm2. No significant difference was found on the control efficacy in the treatment of spray volume 22.5 L/hm2 and pesticide dosage 80%, spray volume 15 L/hm2 and pesticide dosage 90%, as well as KES application. The plant protection UAV with a spray volume of 22.5 L/hm2 achieved better droplet deposition on the upper-canopy, and higher control efficacy. Additionally, a spray volume of 22.5 L/hm2 and pesticide dosage of 80% achieved the same cnaphalocrocis medinalis control efficacy as that with the KES with the pesticide dosage of 100%. This finding can provide a sound reference to the parameters set for the plant protection UAV spraying pesticides, thereby promoting the reduction of pesticides in rice.