Operational effects of unmanned helicopters for pesticide spraying in rice field

Objective  To test and compare the operation effects of single-rotor unmanned aerial vehicle (UAV) type HY-B-15L and multi-rotor UAV type MG-1S on pest and disease control in rice field.

Method  The mixing solution of rhodamine-B and nano-pesticide was selected to spray in rice field, and field spraying experiments were carried out by changing the working altitude of helicopter and the amount of pesticide spraying. The polyester fiber cards and water-sensitive papers deposited by droplets were collected and analyzed by fluorescence spectrophotometer and image analysis software “DepositScan” to obtain deposition effects of the droplets.

Result  The deposition of droplets increased with the increase of pesticide application. Compared with 46.67 mL·hm^–2 pesticide, when pesticide application was 66.67 or 100.00 mL·hm^–2, the deposition of droplets sprayed by single-rotor UAV increased by 48.50% or 137.73% respectively, while the deposition of droplets sprayed by multi-rotor UAV increased by 66.60% or 111.88% respectively. The spraying height of UAV influenced the deposition and uniformity of droplets on the sampling point. When the spraying height ascended from 1.5 m to 2.5 m, the deposition and uniformity of droplets decreased by 19.3% and 53.6% respectively for single-rotor UAV, and decreased by 48.7% and 22.9% respectively for multi-rotor UAV. The spraying performances of single-rotor UAV were better than those of multi-rotor UAV under four spraying conditions. Compared with multi-rotor UAV, the deposition of single-rotor UAV increased by 85.8%, 26.5%, 59.4% and 123.4% from treatment 1 to treatment 4. When single-rotor UAV worked at the height of 1.5 m and a dosage of 46.67 mL·hm^–2, the preventive effect of pesticide was the best which were 87.63%, 76.67%, 84.08%, 59.26% and 82.33% respectively against Nilaparvata lugens, Cnaphalocrocis medinalis, Chlorops oryzae, bacterial leaf streak and rice blast. When multi-rotor UAV worked at 1.5 m and a dosage of 66.67 mL·hm^–2, the preventive effects against those rice pests and diseases were close to the former and were 86.54%, 78.62%, 89.47%, 66.67% and 83.33% respectively.

Conclusion  Because of different wind field below the UAV rotor, the droplet deposition of two UAVs are different. The spraying effect of single-rotor UAV is better than that of multi-rotor UAV, but there is no significant difference of control effect between two UAVs. The preventive effects of pesticides sprayed by both UAVs can reach the criterion of China.