An experiment was designed and setup for Objective 3, Effect of Fe2+ and citric acid treatment on HLB titer of model HLB system determined. The experiment tests Treatment Solution B reported in Patent US 8,945,631, Liquid for treatment of citrus greening disease and treatment method using same. Greenhouse-grown citron plants propagated from HLB-infected citron were tested by RT-PCR. Thirty-six plants that tested positive and showed HLB symptoms were planted into Ruck’s pots. The experiment included 3 treatments applied to three groups of twelve plants. The treatments included Treatment Solution B at two concentrations – 30 ppm Fe and 150 ppm Fe. 30 ppm Fe was the concentration used in the field experiment of the patent. 150 ppm Fe was the upper limit of Treatment Solution B the patent’s authors thought was possible without significant phytotoxicity. Treatment Solution B is applied to foliar and soil at 150 ppm Fe weekly. For soil, 40 mls is added to each pot. The testing of F11 as described in the February, 2019 report continues. A third experiment to determine the phytotoxicity threshold of F11 and Treatment Solution B was initiated. Citron cuttings were taken, planted, and plants selected. Eight iron treatments, including an untreated control, and 12 replicates arranged in a randomized block design were finalized. The 8 iron treatments include 1) F11 applied to foliar-only to runoff; 2) F11 @2X to foliar + soil; 3) F11 @10X to foliar + soil; 4) Fe chelate mixture applied to foliar + soil; 5) Sequestrene 138 (a standard Fe treatment) to foliar + soil; 6) Treatment Solution B applied to foliar + soil; 7) a proprietary iron mixture with high Fe2+ to foliar + soil; and 8) an untreated control receiving standard recommended citrus nutrition. With the exception of the Fe chelate mixture (#4) and Sequestrene 138 (#5), all Fe treatments are high Fe2+ and meet the patent’s specifications for the use of Fe2+ to manage HLB. To determine the number of replicates a power analysis was conducted using tree quality and fruit yield data from the subcontractor’s field site (Florida Research Center for Agricultural Sustainability, Vero Beach, FL) where the field experiments will be conducted. The analysis calculated the number of replicates required to detect a difference between treatments that would be of sufficient size to be useful for managing HLB. For tree condition, measured on a 0-4 scale, an 18% difference can be reliably detected. For boxes/tree, a 124% difference between treatments can be reliably detected. Both measures used 12 replicates and the standard 5% significance and 80% power thresholds. Based on this analysis 96 uniform Red Grapefruit trees on USDA 897 rootstock (P.D. 12/19/18) have been randomly assigned to one of the eight treatments in 12 replicated plots using a Randomized Complete Block (RCB) design. Trees were allowed time to establish root systems and exposure to native population of ACP before treatment applications. This supports Objective 7, Determine the effect of Fe2+ + organic acid solutions on newly planted (<2 years old) field trees.