Field variety trials are a simple but effective tool to test plant horticultural performance under different environmental conditions and enhance the commercial adoption of new cultivars. Large-scale, rapid implementation of HLB-tolerant cultivars depends on reliable data, and the Millennium Block project is addressing the need of establishing field plantings to generate regional, updated information for the Indian River Citrus District. The project has two objectives: (i) Assess performance of new grapefruit cultivars with certain rootstocks under HLB endemic conditions 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. Trials tested: T1) grapefruit cultivars on three rootstocks, T2) 38 rootstocks with `Ray Ruby’ grapefruit as the scion, T3) 36 rootstocks with ‘Glenn 56-11′ navel orange, and T4) 36 rootstocks with `UF-950 mandarin. We planted 3,400 trees in Sep/2019 and 1,100 trees in Aug/2020 and are waiting for the remaining trees on UFR rootstocks from 7 through 14 to be delivered by the nursery (Spring/2021). Masters student started on Jan/2020. Controlled-release poly coated fertilizer was applied in Sep/2019, Jan, May and Sep/2020. Irrigation controller, sand media filtration system and water flow meter were installed. The group met with the certified crop advisor to develop a spray program schedule based on time of year and conditions to be applied as determined by IPM scouting. Hoop boom was modified to spray young trees with higher accuracy, reducing the waste of agrochemical products. We created a tree location map and began production and distribution of QR tags to be used with scanner codes during data collection in the field. Tree height, tree width in two positions (E-W and N-S), and trunk diameter were measured in three central trees from each experimental plot in Feb, July and Nov/2020, and canopy volume calculated. The following summary data reflect the best and worst treatments in each trial during the first months of growth. Statistical significance is omitted for the reporting purposes, and data have been presented at the 2020 ASHS annual conference (https://ashs.confex.com/ashs/2020/poster/eposter.cgi?eposterid=367).Although the trials are independent, we observed rootstock performance varied according to the scions used. In Trial 1 (grapefruit), `UF 5-1-99-2′ Pummelette (DPI-435-86) and `US 6-16-172′ Pummelo Hybrid (DPI-847-6172) on US-942 are producing the most vigorous trees. Canopy volume is 8-fold larger (4.28 m3) than `US 1-83-179’ Grapefruit Hybrid (DPI-847-US 1-83-179) on US-942 (0.5 m3). In Trial 2 (grapefruit), trees on A+Volk×Orange 19-11-8 have developed the most robust canopy, with elongated branches that can reach the ground. Overall, trees on A+Volk×Orange 19-11-8 are 3-fold larger (3.91 m3) than Orange 16 (1.24 m3). In Trial 3 (navel orange), C-22 is outperforming all rootstocks with the development of a dark green, thick canopy that is 2.5 times larger (2.67 m3) than the poorest performer, Willits (0.95 m3). In Trial 4 (mandarin), US-812 grew 3-fold larger (2.01 m3) than the lower performers Sun Chu Sha and Cleopatra mandarins, US-1283, C-57 Furr and Orange 16 (0.13 m3) in the mandarin trial. Asian citrus psyllids, Diaprepes root weevils, whiteflies, and other insects are less abundant in the field, except for leafminers, which caused severe damage due to the excessive rainfall and wind gusts that made pesticide application challenging during this quarter. Nonetheless, tree growth has not been significantly affected by these pests. Leaf samples for determining HLB incidence were taken from a pool of trees from each experimental plot in May and Sept/2020 and sent to the Southern Gardens lab for analysis; on average, all samples tested negative (no trees with Ct values <32) but there are several positive trees with visible symptoms. Fruit phenology, pests and diseases have been monitored monthly. Canopy thickness, canopy color and HLB incidence have been measured quarterly in all experimental plots.The Ferrarezi Lab organized a very successful drive-thru field day in the project on 10/09/2020 with 49 growers attending (limited by covid-19 regulations). An estimated 24,000 acres of citrus were represented at the event (70% of the current grapefruit industry acreage, highlighting the importance of the event and my program engagement with the industry). Attendees came from local and neighboring counties including St. Lucie, Charlotte, and Okeechobee counties. Another field day took place on 12/10/2020 with 4 large growers and industry leaders.Overall, trees are building up vigorous canopies, and morphological differences among scions/rootstocks are beginning to show. However, longer-term evaluation is required to identify the most promising scions and rootstocks to determine their profitability and capability of meeting grower and market needs.