Precision trunk injection technology for treatment of huanglongbing (HLB)-affected citrus trees-a review

The outbreak and spread of huanglongbing (HLB) disease have brought about tremendous negative effects and economical losses on citrus production all over the world. The scientists have carried out various preventive and therapeutic methods including genetic improvement, seedling detoxification, chemical control, physical control and biological control to contain huanglongbing harmfulness. Compared to other methods, trunk injection technology is a promising, precise and environmentally friendly treatment method which has achieved valuable effectiveness by utilizing various injection apparatus. In this paper, the critical factors influencing the effectiveness of trunk injection implementations are reviewed in multiple aspects including biology, chemistry, ecology and technique. The researchers concluded that the research results of delivering liquid pesticides or antibiotics to cure various tree diseases and manage invasive pests by trunk injection demonstrated remarkable manifestation. Furthermore, the studies and technological tendencies including the trunk injection interactive mechanism and fundamental theories, the specialized injectable chemical substances adapting to different tree species or diseases, the reduction and closure of trunk injuries, the development of high-efficiency trunk injection automatic equipment, etc., are presented and discussed at the end of this paper. The researchers need to carry out fundamental theoretical researches and interaction mechanisms between injection system and target. The development of automated and accurate high-efficiency injection devices and integrated pest management platform with the functionalities of detection, prevention, treatment, environmental monitoring and key technologies of AI, flexible manipulator operations, agricultural sensors, are the promising tendencies of precision agriculture.