The present project investigates timeline of the HLB infection in citrus, as reflected by emission of volatile organic compounds (VOCs) for advanced disease diagnostics. We have completed the preliminary arrangements at the Containment Research Facility (CRF) for the longitudinal study. We have developed experimental plans for plants testing that include testing schedule, randomization of plant position in green house, and work flow (sequence of testing steps with different methods). Supplies and parts necessary for the study have been arranged. An overhaul of instrumentation has been conducted for the study. We have conducted all the necessary personnel hire and training and established schedule tables for the rotation at the facility to ensure complete use of available time at the facility. We have conducted multiple sets of preliminary experiments to develop optimized protocols for the VOC testing using gas chromatography/differential mobility spectrometry (GC/DMS). The current protocol utilizes PTFE bags to envelop the tested branch and purge with dry air. The first sets of data using the developed protocols have been collected. 200 samples for GC/DMS have been collected so far. The data analysis revealed satisfactory data quality for the first sample collected, but poor data quality for consecutive replicate samples. Further improvements to the protocol are currently being considered based on the collected body of data. The improvements include changes in purge with the makeup air and different sample intake time. In parallel, we have conducted development of experimental protocols for mass spectrometry analysis. Specifically, we have conducted sampling using solid-phase microextraction (SPME) sorbents and stir bar sorptive extraction (SBSE). We have conducted sampling of trees in the laboratory conditions, in the greenhouse and at the CRF facility for the gas chromatography/mass spectrometry (GC/MS) analysis. Both the sampling protocols and the GC/MS protocols have been optimized. The collection of volatiles was conducted using active sampling device developed under previous CRF-funded effort. We have discovered that SBSE sampling resulted in large variability of the data. Currently we are investigating the ways to mitigate such variability by modifying sampling procedure. We have received a future-generation GC/DMS device for in-field use from the industry partner, Applied Nanotech Inc. and have been adopting the unit for the greenhouse testing. We have conducted, along with ANI, troubleshooting and modifications of the device. We have also compiled the set of guidelines/recommendations from the end user perspective for further improvements of the design and interface. Glenn Sellar from NASA JPL has visited UC Davis. We have installed the rig for the hyperspectral measurements of citrus canopy at the CRF facility and conducted training of all UC Davis personnel involved in sample collection to assure that we will be able to collect hyperspectral measurements independently as a part of multi-method rotation. Current data analysis is focused on ensuring consistent data are being collected and therefore is focused on unsupervised analysis to observe variations within the collected data. We have presented the VOC study aspect of the collaborative project of early HLB detection at the 2014 Citrus Showcase in Visalia, CA.