Gene Albrigo

University of Florida | UF · Citrus Research and Education Center

This second edition of Citrus , like the original by F.S. Davies and L.G. Albrigo, intends to provide the reader with an updated overview of citriculture from a worldwide perspective. Current theories and technological advances in citriculture are emphasized, citing specific examples of how and where they are used. The text begins with a discussion...

This second edition of Citrus , like the original by F.S. Davies and L.G. Albrigo, intends to provide the reader with an updated overview of citriculture from a worldwide perspective. Current theories and technological advances in citriculture are emphasized, citing specific examples of how and where they are used. The text begins with a discussion...

This second edition of Citrus , like the original by F.S. Davies and L.G. Albrigo, intends to provide the reader with an updated overview of citriculture from a worldwide perspective. Current theories and technological advances in citriculture are emphasized, citing specific examples of how and where they are used. The text begins with a discussion...

This second edition of Citrus , like the original by F.S. Davies and L.G. Albrigo, intends to provide the reader with an updated overview of citriculture from a worldwide perspective. Current theories and technological advances in citriculture are emphasized, citing specific examples of how and where they are used. The text begins with a discussion...

This second edition of Citrus , like the original by F.S. Davies and L.G. Albrigo, intends to provide the reader with an updated overview of citriculture from a worldwide perspective. Current theories and technological advances in citriculture are emphasized, citing specific examples of how and where they are used. The text begins with a discussion...

This second edition of Citrus , like the original by F.S. Davies and L.G. Albrigo, intends to provide the reader with an updated overview of citriculture from a worldwide perspective. Current theories and technological advances in citriculture are emphasized, citing specific examples of how and where they are used. The text begins with a discussion...

This second edition of Citrus , like the original by F.S. Davies and L.G. Albrigo, intends to provide the reader with an updated overview of citriculture from a worldwide perspective. Current theories and technological advances in citriculture are emphasized, citing specific examples of how and where they are used. The text begins with a discussion...

This is a study to create an index to measure the rate of peel matura-tion in citrus as it relates to postharvest handling and keeping quality. Currently, citrus is harvested based on internal quality. Peel changes have not been related to best harvest time. Several physical and chemical parameters were measured for harvest dates to determine if pe...

This study was designed to understand the role of peel maturation in citrus as it relates to postharvest handling and keeping quality of the fruit. Currently, citrus is harvested based on internal quality (edibility). Peel changes have not been related to best harvest time. Peel physical and chemical characteristics may be used to identify peel mat...

This study was designed to understand the role of peel maturation in citrus as it relates to fruit postharvest handling and keeping quality. Currently, citrus is harvested based on internal quality (edibility). Peel changes have not been related to best harvest time. Several physical parameters and chemical parameters were measured at several harve...

The severe citrus (Citrus sp.) disease Huanglongbing (HLB), associated with Candidatus Liberibacter asiaticus, has resulted in widespread tree decline in Florida and overall citrus production is now the lowest it has been in 50 years. More than 80% of Florida citrus trees are HLB affected, and most growers attempt to sustain production on infected...

Citrus is harvested based on internal quality (edibility). Peel changes have not been related to best harvest time. Water stress and growth regulators were applied to induce differences in maturity (advance or delay) to see if any peel physical (weight loss, decay, chilling injury, color index, firmness, and detachment force) or biochemical (TSS: a...

This study evaluated effects of crosswind on the variable rate sprayer application treatments spray coverage and deposition on different citrus canopy sizes. The axial-fan airblast sprayer retrofitted with variable liquid- and air-assist rates was field-tested with different crosswind conditions on small (about 2 m tall and < 1.5 m wide) and medium...

Huanglongbing (HLB) is the most destructive disease that affects citrus worldwide. The disease has been associated with Candidatus Liberibacter. HLB diseased citrus plants develop a multitude of symptoms including zinc and copper deficiencies, blotchy mottle, corky veins, stunting, and twig dieback. Ca. L. asiaticus infection also seriously affects...

Winter weather in the Sao Paulo–Minas Gerais (SP–MG), Brazil, and Florida citrus production areas often varies from adequate to inadequate cold for flower induction and excessive drought for induction in the north of the main Brazilian citrus production area. A program of monitoring winter temperature and rainfall data for farms from near Conchal,...

As in arabidopsis (Arabidopsis thaliana), putative citrus (Citrus) Flowering locus T (FT) homologs are strong promoters of flowering and apparently are key components of the molecular mechanism controlling floral induction in these species. An abundance of citrus FT gene transcripts during floral induction is consistent with the role of their produ...

Cool ambient temperatures (5 to 20 °C) and water deficit are the only factors known to induce flowering in sweet orange (Citrus sinensis). Whereas the effects of cool ambient temperatures on flowering have been described extensively, reports on the mechanisms underlying floral induction by water deficit in sweet orange (and other tropical and subtr...

An axial-fan air-assisted sprayer, adapted with variable rate nozzles and adjustable air-assist flow control, for citrus tree-specific precision spraying, was tested. Static experiments were conducted to determine spray patterns at varied nozzle flow rates and air-assistance settings. Spray patterns confirmed that the sprayer delivered variable liq...

Evaluation of the spray patterns is essential for making adjustments to an agricultural sprayer that would result in less chemical usage, less spray run-off onto the ground, and increased spray targeting accuracy. Therefore, in this study, a vertical patternator was fabricated to evaluate an axial-fan airblast sprayer. The airblast sprayer was retr...

Citrus trees were induced to flower by either exposure to low temperatures or water deficit. In the last decade, several genes considered to be involved in the regulation of flowering have been isolated and their expression characterized in response to low temperature in Citrus. However, reports on the effect of floral-inductive water deficit on th...

Phloem plugging of citrus trees affected with Huanglongbing (HLB) was shown previously to result from two types of materials in sieve elements, callose and a lectin of phloem protein2 (PP2) (Achor et al., 2010). An associated study (Etxeberria et al., 2009) found that diversion of sugars to starch accumulation left the root system of affected trees...

Airborne multispectral and hyperspectral imaging can be used to detect potentially diseased trees rapidly over a large area using unique spectral signatures. Ground inspection and management can be focused on these detected zones, rather than an entire grove, making it less labor-intensive and time-consuming. We propose a method to detect the areas...

This reports a preliminary study to understanding the role of peel maturation in citrus as it relates to postharvest handling and keeping quality of the fruit. Currently, citrus is harvested based on internal quality (edibility). Peel changes have not been related to best harvest time. Several physical parameters (weight loss, decay, chilling injur...

The loss of leaves, branches and flowers along with bark scuffing and root exposure that can occur during mechanical harvesting (MH) has not reduced long term yields of healthy trees. Nonetheless, such visible injuries have limited the widespread adoption of mechanical harvesting in Florida's citrus industry. There was little measurable physiologic...

Huanglongbing (HLB) or citrus greening is a bacterial disease recently discovered in Florida, which threatens the state's multi-billion dollar citrus industry. No cure exists for this disease and tree removal is the only effective control method to prevent the spread of the disease. Currently, scouting and visual inspection is used by growers to id...

Disease detection at early stages is a critical component of managing citrus greening (HLB) disease. Multiple optical sensing techniques for detection of HLB have been investigated. This presentation covers an overview of various sensing techniques and data analysis methods for detection of citrus greening disease. Different approaches such as visi...

An airblast sprayer was modified with individually adjustable volume spray nozzles and an adjustable louver diverter for the lower 60% of air volume. These are to be controlled based on laser sensor determination of tree size and canopy density. A previously designed tower collector for spray pattern was modified to allow collection of spray driven...

This research was carried out on ‘Marsh’ grapefruit and ‘Valencia’ orange, aims to understand the role of peel maturation in citrus as it relates to postharvest handling and storability. Currently, citrus is harvested based on edibility. Peel changes have not been related to best harvest time, but most handling problems are peel related. Changes in...

An airblast sprayer was modified with individually adjustable volume spray nozzles and an adjustable louver diverter for the lower 60% of air volume. These are to be controlled based on laser sensor determination of tree size and canopy density. A previously designed tower collector for spray pattern was modified to allow collection of spray driven...

The diversity and stability of bacterial communities present in the rhizosphere heavily influence soil and plant quality and ecosystem sustainability. The goal of this study is to understand how 'Candidatus Liberibacter asiaticus' (known to cause Huanglongbing, HLB) influences the structure and functional potential of microbial communities associat...

Mode of Fusarium solani penetration into rough lemon citrus rootstock seedling fibrous roots was determined and root symptomatology was evaluated using light, scanning, and transmission electron microscopy. Roots contained limited subepidermal infection 15 h after inoculation. Invasion of epidermal cells was principally through broken epidermal and...

AdditionAl index words. Citrus sinensis, floral induction, shoot maturation, flush growth Three hurricanes from late summer through the fall of 2004 caused severe leaf loss, sometimes over the same citrus production areas in Florida. A vegetative flush occurred after each hurricane, and by December, new shoots were 3 to 12 weeks old prior to trees...

A modeling approach to determine optimal viewing angles that reduce the impact of signal mixtures in orchards was evaluated on citrus. Orchards statistics from high-resolution images in Florida and Western Cape province (South Africa) citrus producing areas show that pixel unmixing between adjacent fields can be avoided for pixel sizes below 10 to...

Linear spectral mixture analysis (SMA) has been used extensively in remote sen-sing studies to estimate the sub-pixel composition of spectral mixtures. The lack of ability to account for sufficient temporal and spatial variability between and among ground component or endmember spectra has been acknowledged as a major shortcoming of conventional SM...

Huanglongbing is a serious phloem limited bacterial disease of citrus now present in Florida. The recommended control includes scouting for the disease symptoms 3 to 4 times per year, tree removal as soon as possible and control of the psyllid vector with frequent insecticidal sprays. Currently, infected trees are stumped with a large cutter-trac...

We determined if winter drought stress could delay flowering and fruit development of immature ‘Valencia’ sweet oranges to avoid young fruit loss during late-season mechanical harvesting. Beginning in December over three consecutive seasons (2007–2009), Tyvek� water-resistive barrier material was used as a rain shield groundcover under 13- to 15-ye...

We determined if winter drought stress could delay flowering and fruit development of immature ‘Valencia’ sweet oranges to avoid young fruit loss during late-season mechanical harvesting. Beginning in December over three consecutive seasons (2007–2009), Tyvek® water-resistive barrier material was used as a rain shield groundcover under 13- to 15-ye...

This study was undertaken to develop a better understanding of the relationship between symptom development and the nature of the citrus disease, huanglongbing. The most characteristic symptom of huanglongbing (HLB) is the non-symmetrical mottled chlorosis of leaf blades. Starch accumulation and phloem collapse have been associated with symptom dev...

The objectives of this research paper were to 1) compare tree counts between oblique and ortho images and 2) determine the accuracy of tree height measurements from oblique images. Accurate determination of tree count and canopy volume can aid growers in planning some orchard operations and estimating yield. The analytical capability of Feature Ana...

The citrus disease Huanglongbing (HLB or citrus greening) is characterized, among other symptoms, by extraordinary levels of starch accumulation in leaves. This condition denotes imbalances in carbohydrate source sink relationship which in turn may have direct implications in the overall health of HLB-trees and in future strategies to manage the di...

Introduction Diagnostic Methods Citrus Decline and Nutrient Constraints Nutrient Constraints Remediation Summary and Conclusion Literature Cited

Attention to the management of insects that feed on foliar flush growth has increased in Florida citrus as a result of the establishment of invasive plant diseases associated with insects that develop exclusively on flush. Citrus can be monitored to identify peak periods of flush abundance to time insecticide applications for these insects; however...

Huanglongbing (HLB), also known as citrus greening is one of the most destructive disease in citrus due to the non-specific nature of disease symptoms and absence of a reliable early detection method, this disease can not identified in trees effectively in the grove. Hyperspectral imaging may have the potential to detect HLB-in at earlier early sta...

Studies have been conducted to determine growth requirements for fungi belonging to the genus Byssochlamys. Incubation temperature significantly affected growth, with visual detection in 2 days at 30° C and 4 days at 20° C. Sugar concentration was important in liquid culture techniques, with no growth observed in 30° Brix apple drink base after 2,6...

Up to three hurricanes (Charley, Frances, and Jeanne) passed over the same citrus-producing areas of Florida in August and September 2004. In October 2005, hurricane Wilma also passed over South Florida. We began evaluating citrus tree recovery in four commercial groves (red and white grapefruit, and `Murcott' tangerine) following the 2004 hurrican...

In order to evaluate possible reduced nitrate leaching while maintaining yield, `Hamlin' orange and `Flame' grapefruit trees on `Carrizo' or `Swingle Citrumelo' rootstocks were grown from planting using only foliar urea or soil-applied nitrate or ammonium N. An intermediate treatment of foliar and ground N was included also. From the 4th year, yiel...

A production practices scheduling system has been developed that allows coordination of production activities to the proper stage of reproductive growth. The program is driven by a flowering expert system that predicts flowering intensity and date of bloom. Other major phenology stages of fruit development are predicted from bloom date. The floweri...

Recent interest in reducing nitrate levels in ground water has stimulated a re-examination of the potential use of foliar applications of urea on citrus trees. We examined the penetration characteristics of urea through isolated cuticles in relation to their thickness and surface wax content in citrus (Citrus paradisi Macf.) leaves using a finite d...

Copper (Cu) fungicides are contact action products commonly used for control of citrus fungal diseases. Cu residues are subject to weathering (rain and wind) and dilution from fruit expansion during early growth. Growers often over-spray, which leads to inadequate disease control, or under-spray, which leads to environmental concerns and Cu phytoto...

Permanent chlorosis of leaves on plants fertilized with urea containing high levels of the contaminant biuret has been observed in several crops including citrus. Little has been reported as to the cellular changes that result from such chlorosis. Branches from 'ruby red' grapefruit (citrus paradisi macfadyn) and 'hamlin' orange [c. Sinensis (l.) o...

Florida citrus areas were affected by four severe hurricanes (three direct hits) within a 6-week period in August and September 2004. All segments of the Florida citrus industry were impacted either directly or indirectly. Citrus nurseries suffered extensive losses and bearing trees were uprooted, broken or lost leaves and fruit. Compared to the 20...

Grapefruit are susceptible to melanose from initial set until fruit diam. is 6-7 cm, which can span 3 months. Common Indian River melanose-control practice has been application of Cu fungicides at petal fall, with reapplication every three wks. through the infection period. Research data were previously used to develop a computer model to estimate...

Citrus flowering is a complex phenological process influenced by a number of interacting factors. Low winter temperatures are recognized as an important factor, but the flowering response has not been quantified under Variable natural conditions. A study was conducted to monitor the flower bud induction response of 'Valencia' and 'Hamlin' sweet ora...

Yields of fruit tree crops are determined primarily by flowering intensity and subsequent fruit set from those flowers. The processes related to flowering and fruit set are discussed in this mini-review particularly for tropical-subtropical behavior of citrus with some references to subtropical avocado and more tropical mango, litchi, and longan fr...

Commercial application of foliar urea in the winter-time and NPK sprays in the spring-time commonly occur in Florida citrus production because of reported benefits of increased flowering and yield. There were no measurements of actual nutrient uptake accompanying the early work on yield benefits. Biuret toxicity from contaminants in commercial urea...

The authors are part of a Florida group of research, extension and grower personnel engaged in development of an integrated Decision Support System (DSS) to provide growers with recommendations for their citrus production practices. To assist growers in the timing of production practices, a JAVA-based DSS was developed, that includes modules for ph...

Foliar-applied urea nitrogen (N) has potential to become an important component in fertilizer programs for citrus in Florida and other citrus growing areas as it can reduce nitrate leaching into ground water. We evaluated seasonal absorption characteristics of three urea formulations, Triazone-urea, liquid urea, and spray grade urea by citrus leave...

Except for `Orlando' and `Minneola' tangelos, most citrus hybrids grown in Florida are small-flowered and produced less than half the nectar of large-flowered cultivars. Sugar contents in large- and small-flowered cultivars were not different in 1997, but the concentration of sugars doubled in 1998 over 1997 for small-flowered hybrids, while nectar...

Citrus melanose, caused by Diaporthe citri, is a major disease of fresh market grapefruit which is controlled primarily by preventive applications of copper fungicides. The goal of this research was to improve melanose control without increasing the total amount of metallic copper utilized. Disease control was assessed in field experiments for 3 ye...

Temporal studies were conducted from mid- to late-harvest season of 'Ruby Red' grapefruit (Citrus paradisi Macf.) to evaluate the effect of on- and off-tree storage, fruit size, and juice vesicle position on the development of granulation. Juice vesicle fresh and dry masses were highest at the stem and stylar positions of the fruit section and were...

Young expanding leaves of 'Ambersweet' [Citrus reticulata Blanco x C. paradisi Macf. x C. reticulata) x C. sinensis (L) Osb.] with feeding injury by third larval stage of citrus leaf miner (Phyllocnistis citrella) were examined by light and electron microscopy for extent of injury and tissue recovery over time. Results confirmed that injury is conf...

In citrus blight, a decline disorder of unknown etiology, the tree canopy exhibits symptoms of Zn deficiency while Zn accumulates in the trunk phloem. We have purified a Zn-binding protein (ZBP) from phloem tissue of healthy and blight-affected citrus (Citrus sinensis [L.] Osbeck on Citrus jambhiri [L.]). The molecular weight of the ZBP was estimat...

Foliar applications of urea-nitrogen are widely used to alleviate N deficiencies in citrus; however, improper applications can cause serious foliar burn and loss of active green leaf area. Light (LM), transmission (TEM), and scanning (SEM) electron microscopy were used to characterize anatomical and ultrastructural details of foliar burn in citrus....

The recent infestation of Florida citrus by the Asian citrus leafminer required that more information be obtained about the time interval for a flush to expand and the leaf area contributed by flushes in seasons when leafminer populations are likely to increase and cause leaf area loss. Time for leaf and shoot expansion was determined for spring an...

Foliar applications of urea nitrogen (N) is a relatively new practice in Florida citrus production resulting from applied research and changes in citrus fertilizer management philosophy. The present study investigated the effect of leaf age and surface morphology on leaf wettability as measured by contact angles, and absorption efficiency of foliar...

In Florida, pesticides, nutritional and growth regulators are often sprayed in tank mixes to reduce sprayer use. Many individual spray components are phytotoxic and result in spray burns in combination or if applied with adjuvants. The toxicity level of standard spray materials is not known and new product testing for phytotoxicity is not routine....

Upper surface leaf lesions on `Sunburst' mandarin [( Citrus reticulata Blanco × ( C. paradisi Macf. × C. reticulate )] associated with feeding by the citrus rust mite [ Phyllocoptruta oleivora (Ashm.)] are more severe than those on other citrus cultivars. Development of leaf lesions on `Sunburst' mandarin and two other cultivars were examined by li...

In Florida, pounds soluble solids per box (% soluble solids × % juice × weight) can be 60% higher in some years compared to the lowest years. Pounds solids, soluble solids and juice content data were obtained for the different citrus growing districts in Florida for a 20-year period from the USDA and Florida Agricultural Statistics Service. Weather...

Citrus blight is an extremely complex decline disorder of unknown etiology, Zinc accumulates in the phloem of the tree 40-50 cm above the bud union 1-3 years prior to visible symptoms of blight (foliage wilt and twig dieback). This is accompanied by Zn deficits in the leaves. A Zn-binding peptide (ZBP) purified from citrus phloem tissue accounts fo...

Cell wall composition and structure were examined in visually normal (N), granulated (G), and collapsed (VC) juice vesicles of `Marsh Seedless' grapefruit (Citrus paradisi) Macf.). According to gel-filtration data, VC appeared to be associated with a modification of water-soluble (WSP) and chelate-soluble (CSP) pectin molecular weight (M r ); small...

Extracts from Zn-accumulating phloem tissue of blight-affected trees had higher Zn-binding capacity than extracts from healthy trees. A 4-kDa, highly anionic, zinc-binding fraction was isolated from the phloem of predecline and decline stage ‘Valencia’ sweet orange [ Citrus sinensis (L.) Osbeck] and ‘Marsh’ grapefruit (C. paradisi Macf.) trees grow...

Marsh' grapefruit harvested from a Florida Indian River district grove from February through June were wrapped with 60 gauge (15 |xm) polyvinylchloride (PVC) film, polyole-fin (PO) film, perforated polyolefin film, or polybutadiene (PB) film and compared to a waxed control. The fruit were stored at 15.5, 21, and 29.5C (60, 70, and 85°F, respectivel...

Citrus blight is a vascular wilt disease of unknown etiology. Blight-affected ‘Pineapple’ sweet orange [ Citrus sinensis (L.) Osb.] trees on rough lemon ( C. jambhiri Lush.) rootstock in early stages of decline were treated with benzimidazole fungicides or with oxytetracycline (OTC) by trunk injection, soil drench, or injection plus drench. The dis...