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Building a physical barrier around citrus trees or groves can prevent contact between trees and Asian citrus psyllids, the carrier of the pathogen that causes huanglongbing. This new 4-page article is for growers, scientists, and industries that are interested in this approach to protect citrus from huanglongbing. Written by Timothy A. Ebert, Arnold W. Schumann, Laura Waldo, Daniel Stanton, and Philippe Rolshausen, and published by the UF/IFAS Department of Soil and Water Sciences.

The information provided in the 2008 2nd edition is still sound for healthy citrus trees under Florida production conditions. Much of the information provided in this document on nutrients, application methods, leaf and soil sampling and irrigation scheduling are also effective for huanglongbing (HLB) affected citrus trees. However, research conducted since HLB was detected in Florida in 2005 has established changes in many production practices, including nutrient rates, irrigation scheduling, soil pH management, and use of Citrus Under Protective Screen (CUPS). Changes to the 2nd edition of SL253 will appear in boxes similar to this one at the beginnings of chapters 2, 6, 8, 9, and 11.

Using tricalcium phosphate (TCP) to maintain solution P at low concentrations may be a novel approach for increasing root hair proliferation in HLB-endemic citrus groves, potentially improving nutrient uptake and increasing citrus tree health. It is worth noting that mycorrhizal associations with roots can also enhance their surface area for nutrient uptake, with benefits that are similar to root hairs, and that a similar low-P environment is most conducive for optimal mycorrhizal performance.

The following description of citrus fertilizer uptake, soil and leaf testing and nutrient recommendations were taken from SL 253* and reflects citrus nutrient management for healthy trees prior to citrus greening or HLB entering Florida. Additional information on nutrients obtained since the publication was released appear in this document as "the effect of HLB" on various aspects of citrus nutrient management and are noted as such with published papers cited. *Nutrition of Florida Citrus Trees, 2nd Edition By Thomas A. Obreza and Kelly T. Morgan (2008) SL253/SS478: Nutrition of Florida Citrus Trees, 3rd Edition. (ufl.edu) This 9-page fact sheet is part of the 2019–2020 Florida Citrus Production Guide. Written by K. T. Morgan, D. M. Kadyampakeni, M. Zekri, A. W. Shumann, T. Vashisth, and T. A. Obreza, and published by the Agronomy Department, March 2019. CMG13/CG091: 2022–2023 Florida Citrus Production Guide: Nutrition Management for Citrus Trees (ufl.edu)

This 2-page fact sheet is part of the 2019–2020 Florida Citrus Production Guide. Written by A. W. Schumann, A. Singerman, A. L. Wright, and R. S. Ferrarezi, and published by the Horticultural Sciences Department, March 2019. CMG19/HS1304: 2022–2023 Florida Citrus Production Guide: Citrus under Protective Screen (CUPS) Production Systems (ufl.edu)

This 5-page fact sheet is part of the 2019–2020 Florida Citrus Production Guide. This chapter on irrigation management of citrus is largely taken from guidelines provided in SL253 Chapter 9 on trees prior to citrus greening: SL253/SS478: Nutrition of Florida Citrus Trees, 3rd Edition. A section has been added to cover recent findings on water use of trees affected by citrus greening and the impact this would have on the irrigation management considerations. Written by D. M. Kadyampakeni, K. T. Morgan, M. Zekri, R. S. Ferrarezi, A. W. Schumann, and T. A. Obreza, and published by the Agronomy Department, March 2019. CPG12/CG093: 2022–2023 Florida Citrus Production Guide: Irrigation Management of Citrus Trees (ufl.edu)

Fertilization is an important aspect of growing citrus commercially. Citrus tree growth, health, and fruit production and quality are closely affected by plant nutrition. This 3-page fact sheet is part of the 2019–2020 Florida Citrus Production Guide. Written by M. Zekri, A. W. Schumann, T. Vashisth, D. M. Kadyampakeni, K. T. Morgan, B. Boman, and T. Obreza, and published by the Agronomy Department, March 2019. CMG14/CG092: 2022–2023 Florida Citrus Production Guide: Fertilizer Application Methods (ufl.edu)

Water is a limiting factor in Florida citrus production during the majority of the year because of the low water holding capacity of sandy soils resulting from low clay and the non-uniform distribution of the rainfall. In Florida, the major portion of rainfall comes in June through September. However, rainfall is scarce during the dry period from February through May, which coincides with the critical stages of bloom, leaf expansion, fruit set, and fruit enlargement. Irrigation is practiced to provide water when rainfall is not sufficient or timely to meet water needs. Proper irrigation scheduling is the application of water to crops only when needed and only in the amounts needed; that is, determining when to irrigate and how much water to apply. With proper irrigation scheduling, yield will not be limited by water stress. With citrus greening (HLB), irrigation scheduling is becoming more important and critical and growers cannot afford water stress or water excess. Any degree of water stress or imbalance can produce a deleterious change in physiological activity of growth and production of citrus trees. The number of fruit, fruit size, and tree canopy are reduced and premature fruit drop is increased with water stress. Extension growth in shoots and roots and leaf expansion are all negatively impacted by water stress. Other benefits of proper irrigation scheduling include reduced loss of nutrients from leaching as a result of excess water applications and reduced pollution of groundwater or surface waters from the leaching of nutrients. Recent studies have shown that for HLB-affected trees, irrigation frequency should increase and irrigation amounts should decrease to minimize water stress from drought stress or water excess, while ensuring optimal water availability in the rootzone at all times.