Development of a plant protection UAV and evaluating its efficacy in managing rice leaf folder (Cnaphalocrocis medinalis Guenee.)

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Drones (Unmanned Aerial Vehicles, UAV) have revolutionized agriculture by optimizing the use of several farm operations and through reducing input costs. The present study aimed at designing a plant protection UAV and evaluating its efficacy against rice leaf folder. A hexacopter drone was designed by Acharya N G Ranga Agricultural University and designated as “ANGRAU Pushpak-01” with certain specifications and Payload Data suitable for plant protection spraying in rice. Field studies were taken up during kharif seasons (rainy seasons) of 2020 and 2021 in farmers fields of Guntur district of Andhra Pradesh, India on transplanted rice. The test insecticide used in the present study was flubendiamide 480 SC (39.35% W/w). The UAV hexacopter was optimized for its forward flight speed, height of aerial spraying for delivering spray width and for obtaining maximum spray width using standard protocols. Field studies involved five treatments (four replications), a) 100% RDP (recommended dose of pesticide) with UAV, b) 75% RDP with UAV, c) 50% RDP with UAV, d) 100% manual spray with human back pack motorized spray, and e) water spray using UAV in a RCBD fashion. Nursery was raised during both seasons of study and 30-days-old seedlings were transplanted into main fields and treatments were imposed with flubendiamide spray at 60 days after transplanting (DAT). Leaf folder damage was assessed at prior to flubendiamide spray treatment-wise, then periodically and finally at 10 DAS (Days after spray). Grain yields were harvested replication-wise, pooled and assessed treatment wise for both the field studies in successive years. Our results on optimization of spray technology indicated that aerial spray with UAV at a height of 0.6 m above canopy was ideal in delivering maximum spray width. Further, at this height, there was good amount and uniform distribution of flubendiamide as evaluated by HPLC. The flubendiamide at 75% UAV spray could yield uniform deposition on rice canopy (top, medium, and bottom), and is equally effective compared to 100% UAV spray of flubendiamide. Further, UAV sprays at both these concentrations are more effective in terms of droplet distribution compared to 100% UAV spray with human back pack motorized spray. Field studies indicated that leaf folder damage was effectively reduced with flubendiamide sprays at 100% and 75% RDPs with UAV with no significant differences. However, these treatments were significantly superior to 100% RDP of spray using human back pack sprayer. Similarly, grain yields were significantly superior in 100% RDP and 75% RDP-UAV sprayed plots with no significant differences between them. Further, both these treatments were significantly superior to 100% RDP spray using human back pack sprayer in grain yield enhancement. Overall, our results suggested the efficacy of “ANGRAU-Pushpak-01” UAV hexacopter in reducing leaf folder in rice and enhancing grain yields when sprayed with flubendiamide at 75% RDP, thus offering scope for reduced pesticide costs compared to spraying with 100% RDP of flubendiamide using human back pack motorized sprayer under the conditions evaluated.