Objective 1 – Determine the effect of the ratio and concentration of Fe2+ + organic acid on hydroxyl radical production and stability. Objective complete. Objective 2 – Determine the phytotoxic levels of Fe2+ + organic acid solutions on citrus. Objective complete. Objective 3 – Determine the effect of Fe2+ + organic acid solutions on HLB titer using a rapid greenhouse, HLB-infected citron, rooted shoot bud assay. Continuing work to develop a rapid greenhouse screening system. Current systems are not yet ready for screening methods to cure or manage HLB. Experimentally robust screening systems are probably the single most important research tool that are needed by the HLB research community. Objective 4 – Requires screening system – see objective 3 discussion.Objective 5 – Requires screening system – see objective 3 discussion. Objectives 6 and 8 (Note: there is no 7) – These are the field tests for the various ferrous iron (Fe2+) and citric acid treatments on HLB status and horticultural measures for both mature (HLB symptomatic) and nonbearing (non-symptomatic) trees. The seven treatments have been applied according to the schedule specified in the project protocol to both bearing and nonbearing age class trees. The nonbearing trees as a class continue to exhibit vigorous growth and are maturing with a good canopy density. There were no significant differences in growth between treatments based on trunk calipers measured on 06/05/2020. Interestingly, there were significant differences in the incidence of HLB symptomatic leaves between treatments (Table 1). Three treatments (Aqua F11-C, Tracite Iron and chelated iron) exhibited fewer incidences of HLB leaf patterns than the untreated control (Table 1).———————————————————————————-Table 1. Number of trees with no HLB symptoms. Each treatment is composed of 12 trees. Treatment # of Trees w/ no HLB Symptoms F11-C (30 ppm) 7 F11-C (60 ppm) 6 Tracite 5% Fe 7 FRC 249 4 Chelated Fe 10 Ferrous sulfate + citric acid 6 Fe Solution 2 Control 5 ———————————————————————————- Aerial images were taken of the young trees and images processed by machine learning to extract various size and shape measures, including canopy area (2D) and canopy density. These data were analyzed and no significant differences were detected between the treatments and the untreated control trees. The bearing grapefruit trees as a class were abandoned on 03/01/2020 due to severe decline caused by irreversible root damage, primarily due to the Phytophthora/Diaprepes complex exacerbated by HLB. Aerial images have been taken of the mature (bearing age) plot immediately prior to tree removal. Images are ready for processing, quantification, and analysis. Also, tree condition assessments, crop yield, and fruit drop counts were made and documented in early January 2020 and revealed no significant differences between treatments. Throughout this quarter as well as the project timeline, conventional pesticide spray applications were applied to all the treatments in the trial and were based on scouting and were in accordance with IFAS guidelines. Similarly, irrigation events were made based on tree and field conditions as determined by soil feel and appearance, tensiometer readings, water table observation well measurements and visual assessment of tree canopy. Fertilizer applications were made via fertigation and were `spoon fed’ with frequent small applications bi-weekly. No dry fertilizer was used.