Oxytetracycline injection using automated trunk injection compared to manual injection systems for HLB-affected citrus trees

Abstract

The manual injection of therapeutic materials to trees is laborious and time-consuming, posing implementation challenges for commercial citrus growers. Compared to manual injection, a previously developed automated trunk injection mechanism reduced the labor required and the size of the injection port. The injection system has now been field-tested on HLB-infected Glen Navel orange trees grafted onto ’Swingle’ citrumelo rootstock while applying oxytetracycline hydrochloride (OTC) and water. The multi-puncture drill-free injection mechanism creates injection ports using a needle attached to an end effector and delivers the required volume of liquids using a metering pump. Injection parameters, including injection duration, pressure, and flow rate, were examined while performing injections, and a comparison was made with a manual trunk injection device commonly used for OTC injection of HLB-affected citrus trees. Maximum pressure was not significantly different between the automated and manual injection systems and for the different liquids injected (100 ml of 5500 ppm OTC, 11000 ppm OTC, and deionized water) as 0.1735 ± 0.054 MPa. However, the automated system had a significantly higher flow rate, decreasing injection duration by 81 times compared to the manual injection. Modifications and improvements to the previously developed automated injection system are also described, including the development of a clog-free needle, automation of the positioning arm, and a control system capable of delivering precise volume to each injection port on both sides of a tree trunk.