A large-scale trial of greening-tolerant citrus cultivars is addressing the need of Indian River growers to know what are the best rootstocks and scions for growing fresh fruit. The project has two objectives: (i) Assess the performance of new grapefruit cultivars with certain rootstocks in the IR district; and (ii) Evaluate the influence of UFR and other recent rootstocks on grapefruit, navel, and mandarin in the IR in comparison to legacy/standard rootstocks. There are four trials: Trial 1) 18 grapefruit cultivars on three rootstocks; Trial 2) 32 rootstocks with Ray Ruby grapefruit as the scion; Trial 3) 31 rootstocks with Glenn F-56-11 navel orange as the scion; and Trial 4) 31 rootstocks with UF-950 mandarin as the scion. In June 2021, 400 tress were planted to add to the 4,500 trees planted the previous two years. The final 90 grapefruit trees on UFR-8 rootstock will be planted in September 2021. In August 2021, leaf and soil samples were collected from each experimental plot to properly manage fertilizer requirements. Controlled-release polycoated fertilizer was applied appropriately in July 2021. All trees were treated biweekly with appropriate agrochemicals to manage canker, Asian citrus psyllid, mites, and citrus leafminers. Tree height, tree width in cardinal directions (E-W/N-S), and trunk diameter were measured on three middle trees in each experimental plot in June 2021 to quantify canopy volume and tree size. Results to date were presented by MSc student Martin Zapien at the 2021 American Society for Horticultural Sciences in Denver, CO, in August 2021. Martin placed 3rd in the Scholar’s Ignite Competition. Tree size data from June 2021 show some scion/rootstock combinations are exhibiting significant differences in canopy volume. In Trial 1, Pummelette UF-5-1-99-2 grapefruit on US-942 is 9.1X larger (7.3 m3) than US 1-83-179 grapefruit hybrid on sour orange (0.8 m3). In Trial 2, grapefruit on UFR-15 is 2.5X larger (5.5 m3) than on UFR-17 (2.2 m3). In Trial 3, navel orange on US-802 is 2.2X larger (3.7 m3) than on Willits (1.7 m3). In Trial 4, mandarin on C-22 is 2.2X larger (4.3 m3) than on 46×20-04-6 (2.0 m3). Longer-term evaluation is needed to identify the most promising scions and rootstocks to determine their profitability and capability of meeting grower and market needs. Greening disease is spreading in the field as visual greening symptoms are on average 25% (up to 60%) of the total tree canopy volume. Leaf samples for quantifying CLas titer were collected in March 2021 and sent to Southern Gardens for analysis. Trees that are CLas-free (ct values >32) and CLas-infected (ct values of 26-32) can be found in the same plots, but many symptomatic trees are developing vigorous canopies. Many trees are bearing their first fruits. The incidence of Asian citrus psyllids, Diaprepes root weevils, whiteflies, leafminers, and citrus canker was quite apparent during the summer due to abundant rainfall and the emergence of a large amount of flush. Leafminer damage has been substantial. Nonetheless, tree growth has not been significantly adversely affected by these pests due the biweekly application of agrochemicals. The second field day to exhibit this project will take place on October 14, 2021.