2012 Annual Report 1a.Objectives (from AD-416): To determine the role of calcium nutrition in citrus in relations to plant growth and tolerance to citrus canker and Huanglongbing (HLB). 1b.Approach (from AD-416): Conduct factorial experiments to isolate the effects of calcium on root and shoot growth and tolerance to citrus pathogens. Fertilizer treatments will be conducted under "clean" (i.e. no plant pathogens) in a protected-environment structure (i.e. greenhouse). Citrus trees will then be moved to the field where citrus canker and HLB are prevalent. Citrus trees will continue to receive their respective treatments in the field and will be routinely monitored for development of aforementioned citrus pathogens. 3.Progress Report: This project is related to Objective 1 of the in-house project: Gain fundamental knowledge of the plant-substrate-water-nutrient system. All citrus trees receiving supplemental calcium nitrate treatments have tested positive for citrus greening during the reporting period. These infected trees, however, in general, appear “healthy” and are productive.