Citrus Rootstock Propagation: Traditional Techniques and Recent Advances

Freshly cut single internodes placed in potting mix with leaf blade attached but reduced in size

Commercially grown citrus trees are usually composed of two parts: 1) the scion, which is the aboveground portion of the tree that produces the fruit, and 2) the rootstock, which comprises the root system and the lower portion of the trunk. This new 4-page publication, chapter 6 of the forthcoming Citrus Nursery Production Guide, discusses three kinds of rootstock propagation: seed, cuttings, and tissue culture. Written by Ute Albrecht, Lorenzo Rossi, and Mongi Zekri and published by the UF/IFAS Horticultural Sciences Department.
https://edis.ifas.ufl.edu/hs1329

Citrus Production Guide: Plant Growth Regulators

Citrus groves around Lake Alfred, Florida. Oranges, fruit, trees. UF/IFAS Photo by Tyler Jones.

Plant growth regulators (PGRs) are a tool used to manipulate vegetative and reproductive growth, flowering, and fruit growth and development. PGRs have been successfully used in agriculture for decades to amend plant growth characteristics to maximize yield and grower profit. This new 4-page fact sheet discusses auxins, gibberellins, cytokinins, abscisic acid, ethylene, new classes of plant hormones, use of PGRs for HLB-affected trees, and general considerations for PGR use in Florida citrus groves. Written by Tripti Vashisth, Chris Oswalt, Mongi Zekri, Fernando Alferez, and Jamie D. Burrow, and published by the UF/IFAS Horticultural Sciences Department, February 2018.
http://edis.ifas.ufl.edu/hs1310

Irrigation Management of HLB-Affected Trees

Water is a limiting factor in Florida citrus production due to non-uniform rainfall distribution and the low water-holding capacity of our sandy soils. Because periods of low rainfall coincide with critical stages of citrus production, additional irrigation is necessary to reduce the negative effects of water stress. This 6-page document covers recent findings on water use of trees affected by citrus greening and the impact this would have on irrigation management considerations. Written by Davie Kadyampakeni, Kelly Morgan, Mongi Zekri, Rhuanito Ferrarezi, Arnold Schumann, and Thomas A. Obreza and published by the UF/IFAS Department of Soil and Water Sciences, October 2017.
http://edis.ifas.ufl.edu/ss659

Canopy Management of Citrus Trees

Tree canopy and bearing volume are two important factors in fruit production and fruit quality; generally, trees with larger canopy volumes produce more fruit than smaller-canopy trees. Therefore, canopy management is an important aspect of citrus production in Florida to avoid problems associated with overcrowding and excessively tall trees. This three-page document describes canopy management practices for citrus growers. Written by Tripti Vashisth, Mongi Zekri, and Fernando Alferez and published by the UF/IFAS Horticultural Sciences Department, October 2017.
http://edis.ifas.ufl.edu/hs1303

Citrus Propagation

Plant propagation is the art and science of reproducing plants while preserving their unique characteristics from one generation to the next. This 6-page document, written by Ute Albrecht, Mongi Zekri, and Jeffrey Williamson, describes the propagation process for commercial citrus. Published by the UF/IFAS Horticultural Sciences Department, October 2017.
http://edis.ifas.ufl.edu/hs1309

Citrus Production Guide: Rootstock and Scion Selection

Oranges on trees in a grove at the Citrus Research and Education Center. Photo taken on 03/04/16.When preparing for replanting, an important factor to consider is the choice of rootstock. Choosing the right rootstock and scion combination can result in higher economic returns without any additional cost. Rootstocks affect scion vigor, yield, fruit size, juice quality, and pest tolerance. However, tree growth, yield, and fruit quality interact strongly with climate, soil type, tree spacing, and other factors, often producing contradictory reports on rootstock performance in different areas. This 3-page fact sheet discusses soil characteristics, rootstock effects on pests and diseases, tree spacing and size, and rootstock/scion combination. Written by Ute Albrecht, Fernando Alferez, and Mongi Zekri, and published by the UF/IFAS Department of Horticultural Sciences, September 2017.
http://edis.ifas.ufl.edu/hs1308

Citrus Irrigation Management

A farmer operating an IFAS-developed mobile app to control citrus irrigation.The chapter on irrigation management of citrus is largely taken from guidelines provided in SL253 on trees prior to Huanglongbing (HLB) prevalent conditions. A section has been added to cover recent findings on water use of trees affected by HLB and the impact this would have on the irrigation management considerations. This 6-page fact sheet discusses water supply, allowable soil water depletion, irrigation scheduling, soil moisture measurement, water budgeting, smartphone apps, irrigation strategies to improve nutrient uptake and reduce leaching, and irrigation management considerations for HLB-affected trees. Written by Davie Kadyampakeni, Kelly Morgan, Mongi Zekri, Rhuanito Ferrarezi, Arnold Schumann, and Thomas Obreza, and published by the UF/IFAS Soil and Water Sciences Department, September 2017.
http://edis.ifas.ufl.edu/ss660

Fertigation for Citrus Trees

Oranges on trees in a grove at the Citrus Research and Education Center. Photo taken on 03/04/16.

Microirrigation is an important component of citrus production systems in Florida. For citrus trees, microirrigation is more desirable than other irrigation methods for several reasons: water conservation, fertilizer management efficiency, and freeze protection. Research has shown that when microirrigation systems are properly managed, water savings can amount to as much as 80% compared with subirrigation and 50% compared with overhead sprinkler irrigation. Research has also shown the important advantage of microsprinklers for freeze protection of citrus. This 4-page fact sheet discusses fertilizer solubility and some common fertigation materials. It also offers a fertigation summary. Written by Mongi Zekri, Arnold Schumann, Tripti Vashisth, Davie Kadyampakeni, Kelly Morgan, Brian Boman, and Tom Obreza, and published by the UF Horticultural Sciences Department, September 2017.
http://edis.ifas.ufl.edu/hs1306

Grove Planning and Establishment

Orange grove.

Many factors need to be considered when preparing for new tree plantings. Careful planning and preparation is necessary to ensure success and reduce future frustrations. This three-page document describes the factors that contribute to the success of new grove establishment. Written by Mongi Zekri, Ute Albrecht, Christopher Vincent, and Tripti Vashisth and published by UF’s Horticultural Sciences Department, September 2017.
http://edis.ifas.ufl.edu/hs1302

Citrus Nutrition Management Practices


A new two-page fact sheet has been published by the Horticultural Sciences Department and the UF/IFAS Citrus Research and Education Center about citrus nutrition management practices. It was written by J.D. Burrow, T. Vashisth, M. Zekri, S.H. Futch, and A. Schumann.
http://edis.ifas.ufl.edu/hs1292

Freeze Damage Symptoms and Recovery for Citrus

Figure 6. Fruit drop in citrus after a severe winter freeze. Credits: Mongi Zekri, UF/IFAS
Citrus trees are evergreen, never become fully dormant, and cannot withstand temperatures as low as those tolerated by deciduous trees. But citrus trees can become preconditioned or acclimated to cool air temperatures that occur in late fall and winter. One of the best ways to lessen cold injury and to hasten recovery from cold damage is to maintain healthy trees. This five-page fact sheet discusses the symptoms of freeze damage and ways to help recover trees that have been damaged. Written by Mongi Zekri, Chris Oswalt, Steve Futch, Gary England, Camilly McAvoy, Laurie Hurner, and Parker Platts, and published by the Horticultural Sciences Department.
http://edis.ifas.ufl.edu/hs1250

Mechanical Pruning of Citrus Trees

Topping and hedging of large citrus trees
When citrus trees are not regularly pruned, less sunlight reaches the lower parts of the trees, which can reduce flowering and fruit development, quality, and color. Less sunlight also increases the risk of fungal infection. This 3-page fact sheets explains how growers can prune trees to maximize light exposure. Written by Mongi Zekri, and published by the UF Department of Horticultural Sciences, August 2015.
http://edis.ifas.ufl.edu/hs1267

Boron (B) and Chlorine (Cl) for Citrus Trees

Figure 1. Boron deficiency—Small size and misshapen fruit, thick albedo containing gum pockets, and aborted seeds with gum deposits around the axis of the fruit.Since mineral nutrition is a major factor in maximizing yield of high-quality fruit, understanding the functions of mineral elements, diagnosing nutrient deficiencies, and providing needed fertilizers are essential. This 4-page fact sheet describes and discusses boron (B) and chlorine (Cl) deficiencies, functions, and recommended practices to alleviate nutritional problems. Written by Mongi Zekri and Tom Obreza , and published by the UF Department of Soil and Water Science, March 2014.
http://edis.ifas.ufl.edu/ss619

Molybdenum (Mo) and Nickel (Ni) for Citrus Trees

Figure 1. Molybdenum deficiency—Large interveinal chlorotic spots Since mineral nutrition is a major factor in maximizing yield of high quality fruit, understanding the functions of mineral elements, diagnosing nutrient deficiencies, and providing needed fertilizers are essential. This publication describes and discusses molybdenum (Mo) and nickel (Ni) deficiencies, functions, and recommended practices to alleviate nutritional problems.This 3-page fact sheet was written by Mongi Zekri and Tom Obreza , and published by the UF Department of Soil and Water Science, March 2014.
http://edis.ifas.ufl.edu/ss618

Iron (Fe) and Copper (Cu) for Citrus Trees

Figure 1.  Iron deficiency symptomsSince mineral nutrition is a major factor in maximizing yield of high-quality fruit, understanding the functions of mineral elements, diagnosing nutrient deficiencies, and providing needed fertilizers are essential. This publication describes and discusses iron (Fe) and copper (Cu) deficiencies, functions, and recommended practices to alleviate nutritional problems. This 7-page fact sheet was written by Mongi Zekri and Tom Obreza, and published by the UF Department of Soil and Water Science, March 2014.
http://edis.ifas.ufl.edu/ss617

Manganese (Mn) and Zinc (Zn) for Citrus Trees

Figure 1.  Manganese deficiency symptomsSince mineral nutrition is a major factor in maximizing yield of high-quality fruit, understanding the functions of mineral elements, diagnosing nutrient deficiencies, and providing needed fertilizers are essential. This publication describes and discusses manganese (Mn) and zinc (Zn) deficiencies, functions, and recommended practices to alleviate nutritional problems. This 5-page fact sheet was written by Mongi Zekri and Tom Obreza , and published by the UF Department of Soil and Water Science, March 2014.
http://edis.ifas.ufl.edu/ss616

Calcium (Ca) and Sulfur (S) for Citrus Trees

Figure 2. These fruit show calcium deficiency symptoms; they are undersized and misshapen with shriveled juice vesicles. Credit: Dr. R. C. J. KooCalcium and sulfur are sometimes called secondary nutrients. This term does not mean that these nutrients play a secondary role in citrus plant growth and development. Ca and S are as essential as N, P, K, Mg, and other nutrients for healthy plant growth. An inadequate supply of Ca and/or S can be a major constraint to crop production and quality. This 5-page fact sheet was written by Mongi Zekri and Tom Obreza, and published by the UF Department of Soil and Water Science, July 2013.
http://edis.ifas.ufl.edu/ss584

Potassium (K) for Citrus Trees

Figure 1. One symptom of potassium deficiency is small fruit. Credit: M. ZekriCitrus fruits remove large amounts of K compared to other nutrients. Potassium moves from leaves to fruit and seeds as they develop. Potassium is necessary for several basic physiological functions such as the formation of sugars and starch, synthesis of proteins, normal cell division and growth, and neutralization of organic acids. Potassium is important in fruit formation and enhances fruit size, flavor, and color. This nutrient also helps to reduce the influence that adverse weather conditions (such as drought, cold, and flooding) have on citrus trees. This 4-page fact sheet was written by Mongi Zekri and Tom Obreza, and published by the UF Department of Soil and Water Science, July 2013.
http://edis.ifas.ufl.edu/ss583

Phosphorus (P) for Citrus Trees

Figure 1. A thick rind and hollow core are both symptoms of P deficiency in citrus trees. Credit: Dr. R.C.J. RooPhosphorus deficiency is not common in Florida citrus groves. If it does occur, it is more difficult to diagnose than nitrogen (N) deficiency or other nutrient element deficiencies. Growth is reduced when P supply is too low. Phosphorus is highly mobile in plants, so when it is deficient, it may move from old leaves to young leaves and other actively growing areas where energy is needed to form seeds and fruit. This 4-page fact sheet was written by Mongi Zekri and Tom Obreza, and published by the UF Department of Soil and Water Science, July 2013.
http://edis.ifas.ufl.edu/ss581

Magnesium (Mg) for Citrus Trees

Figure 2. The leaves on this citrus tree show magnesium-deficiency symptoms. Notice how the leaves have an inverted V-shaped area pointed on the midrib. Credit: M. ZekriMagnesium deficiency has been a major problem in citrus production. In Florida, Mg deficiency is commonly referred to as “bronzing.” Trees with inadequate Mg may have no symptoms in the spring growth flush, but leaf symptoms develop as the leaves age and the fruit expand and mature in the summer and fall. Magnesium deficiency symptoms occur on mature leaves following the removal of Mg to satisfy fruit requirements. This 4-page fact sheet was written by Mongi Zekri and Tom Obreza, and published by the UF Department of Soil and Water Science, July 2013.
http://edis.ifas.ufl.edu/ss582