Objective 1: Leaf nutrient thresholds We requested a 6-month no cost extension for the project in order to make up for lost time after hurricane Irma in 2017. The collection of survey data is now complete and the remaining months until December 2018 will be spent completing and cross-checking the comprehensive analyses and particularly the validity of results and recommendations for growers. Objective 1: Leaf nutrient thresholds Samples from all the sites have been processed and the first phase data analysis is complete. Using stepwise multiple regression and artificial neural networks, this phase screened the entire survey database of some 119,000 data points collected over three years for significant correlations between measured variables and tree performance. We then used these selected data for more intensive linear regression ANOVA testing, followed by Cate-Nelson analysis whereby the data sets were segregated into responsive and unresponsive groups. At the intersection of the two groups we identified the critical threshold values (CT) for deficiency of the leaf nutrient concentrations. These CTs will be useful in future to guide growers how much fertilizer to apply to specifically the HLB-affected groves. We need to re-analyze and cross-check all the results before we are ready to release the new advisory CTs. Objective 2: Determine soil conditions that favor root hair and VAM proliferation Based on the preliminary successful results from the Murcott seedling experiment, where tricalcium phosphate promoted root hair growth, we decided to repeat the experiment with a rootstock seedling. We have 3 new tanks running with 9 Carrizo seedlings each. We are utilizing three nutrient solutions, 1. Complete fertilizer, 2. Complete fertilizer minus Phosphorus, with Rock Phosphate (RP) as the source of Phosphorus, and 3. Complete fertilizer minus Phosphorus, with Triple Calcium Phosphate (TCP) as the source of Phosphorus. Root hair development seems enhanced in the low P, high Ca environment and will be studied closer over the next few weeks, utilizing the microscopy lab to quantify and identify root hair development in each treatment.