The Effect of Huanglongbing on Young Citrus Tree Water Use

Understanding the role of Huanglongbing (HLB) caused by Candidatus Liberibacter asiaticus on citrus ( Citrus sp.) water use is critical for determining if changes in water management of commercial citrus orchards affected by this disease is necessary. Reference evapotranspiration (ET o ) is the most used methodology for irrigation scheduling, particularly in light of reports that indicate the lack of water for irrigation will become a major problem in many places around the world including Florida. The objectives of this study were to determine citrus tree water relationship [water use, sap flow, and stem water potential (Ψ)] as affected by ET o and HLB. The study was initiated on Jan. 2014 on two sweet orange ( Citrus sinensis ) cultivars included Hamlin and Valencia grown in a fine sandy soil texture (sandy, siliceous, and hyberthermic Arenic Alaquods) in a greenhouse. Twelve weighing lysimeters of each cultivar (six HLB-affected and six nonaffected trees) were used to determine selected water relation parameters. Results indicated a significant reduction in water use, Ψ, and sap flow for affected trees when compared with nonaffected trees. Citrus water use of healthy trees during the 2-year study was 31% and 27% greater than HLB-affected trees for ‘Hamlin’ and ‘Valencia’, respectively. Lower water use of HLB-affected trees resulted in 10% and 15% greater available soil water content than healthy ‘Hamlin’ and ‘Valencia’ trees, respectively. Therefore, reducing the water supply for HLB-affected trees than healthy trees may be a desirable practice that would lead to significant water savings.