Pruning and Controlled-Release Fertilizer to Rehabilitate HLB Trees

Abstract

Previous research has shown that HLB-affected trees have a reduced root system and a higher rate of root turnover. In a greenhouse experiment, a significant imbalance in in root to shoot ration was observed in HLB-affected trees as compared to same age healthy trees (Figure 2).  The diminished root system cannot support the existing above ground canopy and production of fruit; as a result, the tree enters into a continuous carbohydrate stress cycle and declines in health.  Imbalance of the root to shoot biomass is detrimental as the vicious cycle of imbalance intensifies as the carbohydrate stress continues. Therefore, pruning to correct the root- to-shoot ratio can be beneficial for trees. In addition to pruning, it is important to promote rejuvenation of the tree for which plant nutrition plays a critical role in regrowth and development. HLB-affected trees have a smaller root system therefore the nutrient uptake is limited at any given time. Thus, it seems reasonable that a small and constant supply of nutrients throughout the growing season should provide the stressed root system a better chance to effectively take up nutrients.