Evaluation of Impacts of Mechanically Harvesting High-density Semi-dwarf Citrus on Tree Health and Yield

In the 1990s, Florida had 845,000 acres of citrus and was competitive with Brazil. That number has since reduced to approximately 531,500 acres due to hurricanes, canker eradication program, urban development, economic downturn, and finally the discovery and spread of Huanglongbing (HLB), which causes tree decline and death. Many of the factors affecting the Florida citrus industry also concern other citrus producing states—such as Texas, Arizona, and California. The national threat of HLB has set the stage for developing new approaches and technologies for citrus production and harvesting that secure a future means to thrive in the midst of various invasive diseases and pests. One approach being considered is Advanced Citrus Production and Harvesting Systems (ACPHS), which uses high density semi-dwarfed trees, and intensive fertigation with optimized nutrient and water availability that accelerates plant growth. Adopting ACPHS for citrus production could increase yield production per acre, while simultaneously shortening the time to return on investment, meaning that grove life can be shortened by disease pressure and still remain economically viable. However, this new grove architecture presents new engineering problems for managing production and harvest of citrus groves. Since ACPHS has smaller trees planted at high density with limited opera­tional area, existing machines are not suitable. One reoccurring challenge to the adoption of mechanical harvesting technology is grower concerns about the impact of mechanical harvesting on tree health, next year’s crop, and fruit damage. This concern has been amplified due to the presence of HLB, which weakens the tree and could have po­tential negative interaction with tree longevity when trees are vigorously shaken by the harvesting machine. In this paper, the authors introduce a new Over the ToP Citrus Harvester (OTPCH), which has been specifically designed for high density semi-dwarf trees, and a multi-year experimental trial that is being conducted to evaluate the impact of harvesting on tree health. The first results of a two-year study are presented. Tree health indicators are measured in the field before and after harvest.