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Huanglongbing (HLB), or citrus greening disease, affects practically all fruitbearing trees in commercial citrus orchards in Florida with no cure identified yet. Highdensity plantings and enhanced nutritional programs such as application of controlledrelease fertilizer (CRF) with higher micronutrient levels can mitigate disease symptoms and extend the tree life span of sweet oranges (Citrus sinensis). The objective of this study was to evaluate the effects of tree planting density and application of CRF blends differing in N to K ratio and micronutrient content on grapefruit (Citrus paradisi) plant health, canopy volume, fruit yield, and fruit quality in an HLB-affected orchard. A study was conducted in Florida for two growing seasons (2017-18 and 2018-19) to evaluate the response of 'Ray Ruby' grapefruit on Kuharske citrange (Citrus sinensis 3 Poncirus trifoliata) to three planting densities (300, 440, and 975 trees per ha) and two CRF blends [12 nitrogen (N)-1.31 phosphorus (P)-7.47 potassium (K) and 16N-1.31P-16.6K] with different nutrient sources and composition. According to quantitative real-time polymerase chain reaction testing, all sampled trees tested positive for Candidatus Liberibacter asiaticus, the pathogen associated with HLB. Trees planted at 975 trees per ha had 33% lower canopy volume per tree but 160% greater fruit yield per hectare and 190% higher yield of solids compared with 300 trees per ha. Fruit produced in high-density planting (975 trees per ha) was 18% more acidic with higher soluble solid compared with low-density planting (300 trees per ha). The use of a CRF blend with higher amounts of micronutrients along with lower Kincreased canopy volume in both seasons and resulted in 24% and 29% reduction in fruit yield per hectare and yield of solids, respectively, in 2017-18. Our results indicate that high-density plantings increase fruit yield per area, and regardless of the N to K ratio, the use of CRF blends supplemented with micronutrients may not increase fruit yield in HLB-affected grapefruit. [ABSTRACT FROM AUTHOR]

Urban tree planting initiatives can experience high levels of mortality during establishment years. Mortality tied to the stresses of transplanting can be partially negated or exacerbated depending on the species selected, nursery materials used, site conditions present, and management practices employed. Past research has quantified post-planting survival, health, and growth. However, varying climates, species, land use types, and management practices warrant additional region-specific research. The purpose of this study is to assess the success of plantings along Florida highways and identify species, site, and management factors related to tree and palm health and establishment. Results show high establishment survival (98.5%) across 21 planting projects ranging from 9 to 58 months after installation (n = 2711). For transplanted palms, the presence of on-site irrigation significantly improved establishment from 96.2% to 99.4%. No establishment differences were detected with regard to irrigation treatment for small-stature trees, shade trees, and conifers. Additionally, there were significant differences in tree health response among tree groups given species, management, and site factors. [ABSTRACT FROM AUTHOR]