Agricultural robots show promising potential for digital farming and handling the problems of workforce shortage and declining profitability. Field robots that autonomously monitor and collect data empower growers with detailed real-time information about their crops and farms, revealing upstream images for making analytical data-driven decisions. Unmanned Aerial Vehicle (UAV) technology combined with image data analytics can provide promising Precision Agriculture (PA) solutions to deal with many of the challenges. In several recent studies, Unmanned Aerial Vehicles (UAV) were used as a sensing platform for disease detection. The development of an autonomous weeding machine and field scouting robot requires a vision system capable of detecting and locating the position of the crop. Such a vision system should recognize the accurate position of the plant stem and protect it during weed control by detecting early disease detection. Based on the available literature, it was found that there is a need for an improved UAV system for online disease identification and targeted delivery of pesticides for plants. This has motivated the current research on deep learning-based plant disease identification and targeted delivery of pesticides using UAV.