Objective 1: We conducted tests with nutrient analyses of leaf samples collected from HLB-infected and healthy trees to establish relationships that could be used for (early) diagnosis of HLB. Starch accumulation in symptomatic leaves can significantly alter the interpretation of nutrient status when diagnosed on a dry weight concentration basis. When corrected for starch accumulation by using specific leaf area, Ca, Mg and B are consistently lower and K is higher in HLB-infected trees compared to healthy trees under the same fertilization program. These changes exist in both symptomatic and asymptomatic leaves from infected trees. Similarly, separation between asymptomatic healthy leaves and asymptomatic infected leaves could be achieved using the Diagnosis and Recommendation Integrated System (DRIS), particularly when assessing the Dry Mass Index (DMI) generated by the method. DMI integrates the imbalances caused by nutrient losses and starch accumulation in HLB-infected leaves, thus could indicate infection early on despite the absence of visible symptoms. Leaf samples have been collected from trees infected with CTV, blight and phytophthora to determine if these changes are HLB-specific or are common changes to all diseases. Those samples undergoing testing for nutrient, starch and disease status. We are working to sample other diseases not currently present in Florida as well (e.g. CVC). Due to stress-related abscission of HLB-symptomatic leaves from the exterior of infected canopies for much of the year, we are often forced to sample symptomatic leaves from within the canopy and asymptomatic leaves from the outside. We tested the effect of this unavoidable sampling position difference on the measured leaf nutrients analyzed in healthy trees and found no significant differences in 11 elements measured. In year two we will continue or research efforts to determine which, if any, of these nutrient changes is a unique response to HLB infection. Objective 2: Five field studies have been established to evaluate the effects of various foliar nutrient applications on the expression of HLB in infected trees by evaluating tree nutrient status, growth, yield and visual tree appearance through photographic documentation. The first trial is a survey-type trial to monitor the health and yield of trees in Maury Boyd’s grove in Felda. We have harvested the same Hamlin and Valencia trees for two seasons in tThe first of these trials is in a heavily infected mature Hamlin grove in south Florida. Since the initiation of the project the trees in this study have received six foliar applications of one of nine different treatments. Untreated trees serve as controls. The trees were harvested in December 2009. This was the first harvest since the beginning of the trial and did not reveal any significant differences among treatments; however, that is not unexpected following only 1-year of treatment. The second study is in a young (3-5 years old) commercial Valencia grove in Haines City. Treatments in this study have been underway for approximately 7 months and include fertigation in addition to foliar nutrient sprays. Our initial efforts at this site have been to demonstrate the ability to raise the levels of specific nutrients involved in plant defenses within trees. Since treatments began, B levels have been successfully raised to near toxic levels within infected and healthy trees using both foliar and fertigation applied B. This has demonstrated that good nutrient uptake can be achieved through the treatment methods in a relatively short period of time. Analysis of the large quantity of these studies have generated is still being analyzed as of the writing of this report. As soon as the analyses are complete information will be passed along to the Florida citrus community. Two additional field studies are currently being started for this season. Objective 3: A hydroponics system has been constructed in an HLB approved greenhouse at the CREC. We previously reported that trees were being established in this system; however, for undetermined reasons those trees did not perform well in the hydroponics system. The project has been revised and new trees are being established in sand culture instead of liquid hydroponics. All of the plants will be maintained with a complete nutrient solution until HLB symptoms develop on the inoculated trees. Previous experience with greenhouse graft inoculation indicates that this will take about 90 days. At that time, healthy and infected trees will be subjected to various changes in the nutrient solution composition. Based on the data from objective 1, the levels of Ca, Mg, and B and combinations of these three nutrients will be changed to determine plant response with and without HLB. Trees remaining in complete nutrient solution will serve as controls. This experiment will allow us to begin to separate nutrient and HLB effects on plant growth and development.