An Automated Delivery System for Therapeutic Materials Using Needle-Based Trunk Injection to Treat HLB Affected Citrus

Direct trunk injection is a promising alternative to foliar spray and soil drenching for delivering bactericides and other therapeutics for managing HLB and its vector. Most of the currently available pressurized trunk injection systems drill relatively large holes, which causes substantial wounding and leaves the tree open to infection and decay. In this project, a multi-hole trunk injection was performed with two different prototypes. In the first prototype, a micro-needle-based (3 mm long) roller fixed on a spring-loaded arm mounted on an electric linear actuator was used for creating holes. The needles were able to penetrate the tree bark to about 1-2 mm depth and the compound uptake was visualized in the vascular tissue of small (trunk diameter less than 20 mm) and medium (20-40 mm diameter) greenhouse trees through the presence of a dye. In the second prototype, a hollow-needle-based pressurized injection system was designed. A hub containing 6 hollow needles (ID: 0.085”, OD: 0.109”) in vertical rows of 3, was mounted at the end of a pneumatic cylinder. The cylinder was able to achieve the target penetration depth (3-8 mm) for 5-year-old field-grown trees (Valencia/Kuharske rootstock). This prototype was modified to reduce needle clogging and avoid the “pushing” effect on the tree by using a different cylinder setup and a revised clamping mechanism for piercing and injection. This automated injection system could potentially reduce the intensity of tree wounding and is a more adaptive, fast, and efficient method compared to existing trunk injection devices.